Showing 1–50 of 127 results for author: Smith, B J

Dynamics of tidal dwarf galaxies in the system Arp 72

Authors: Osvan M. Portilla-Narvaez, Javier Zaragoza-Cardiel, Gisela N. Ortiz-León, Y. D. Mayya, Beverly J. Smith, Chandreyee Sengupta, Mark L. Giroux, S. Comerón, Luz I. Alvarez-Cruz

Abstract: Some interactions between galaxies produce tidal tails primarily composed of material from their disks. Within these tails, concentrations of gas and stars can form, resembling dwarf galaxies. These tidal objects often begin to form stars and become dynamically independent of their parent galaxies, leading to their classification as Tidal Dwarf Galaxies (TDGs). By definition, TDGs should consist s… ▽ More Some interactions between galaxies produce tidal tails primarily composed of material from their disks. Within these tails, concentrations of gas and stars can form, resembling dwarf galaxies. These tidal objects often begin to form stars and become dynamically independent of their parent galaxies, leading to their classification as Tidal Dwarf Galaxies (TDGs). By definition, TDGs should consist solely of baryonic material, with a negligible dark matter fraction. In this study, we analyze the dynamics of two TDGs in the Arp 72 system using high-resolution Hα observations obtained with the MEGARA multi-spectrograph at the GTC (Gran Telescopio Canarias) and neutral hydrogen (HI) data from the GMRT (Giant Metrewave Radio Telescope). The HI data were also used to determine the gas mass. We derived the rotation curves and velocity dispersion from the kinematic data, which allowed us to estimate the dynamical mass of the systems. The TDGs were modeled through 3D fitting as rotating disks with additional pressure support, assuming a mass distribution following an exponential law. The gas mass was combined with the stellar mass to determine the total baryonic mass. Under specific dynamical considerations, we established the relationship between the dynamical mass and the baryonic mass. Additionally, we used the pressure-support corrected circular velocity to compare the behavior of TDGs in the context of the baryonic Tully-Fisher relation (BTFR) with the literature, showing how detached TDGs fall off the relation. The two studied objects are consistent with the expected properties of a TDG. △ Less

Submitted 18 August, 2026; originally announced August 2026.

Comments: Accepted for publication in Astronomy & Astrophysics (A&A). 19 pages, 17 figures

Galaxy Spiral Arm Count vs. Concentration and Mass: A First Look with Euclid

Authors: Beverly J. Smith, Sydnie Bergner, Mark L. Giroux, Curtis Struck

Abstract: Using catalogued information from Euclid Quick Data Release 1, we compare 2-armed and 3-armed spiral galaxies as classified by the Euclid Zoobot software. Two-armed galaxies have larger concentrations, lower stellar masses (M*), and lower star formation rates (SFRs) on average than 3-armed galaxies. For a given M*, 2-armed galaxies have larger concentrations than 3-armed galaxies. These trends hav… ▽ More Using catalogued information from Euclid Quick Data Release 1, we compare 2-armed and 3-armed spiral galaxies as classified by the Euclid Zoobot software. Two-armed galaxies have larger concentrations, lower stellar masses (M*), and lower star formation rates (SFRs) on average than 3-armed galaxies. For a given M*, 2-armed galaxies have larger concentrations than 3-armed galaxies. These trends have been seen before in nearby galaxies; with Euclid we extend the patterns to redshifts z = 0.4 - 1. Two-armed galaxies have lower SFRs because they have lower masses; at fixed M*, 2-armed and 3-armed galaxies have similar SFRs. We see a bend in the concentration-log M* relation for 2-armed galaxies at M* = 10^10.3 M(sun). Above this mass, 2-armed galaxies show significantly larger concentrations than their lower mass counterparts. The observed concentrations of 2-armed galaxies decrease with increasing redshift, perhaps from morphological K-corrections and resolution differences. About 60% - 70% of Euclid spirals are 2-armed, and about 15% - 20% are 3-armed. One-armed galaxies are rare, with low masses compared to 2-armed spirals. We compare these statistics with Galaxy Zoo Sloan Digital Sky Survey arm counts at low z, and tentatively with JWST at higher z. We discuss these results in terms of theoretical models of spiral arm generation and evolution, and compare with statistics of grand design, multi-armed, and flocculent galaxies. There is a need for more quantitative measurements of arm structure beyond arm counts provided by the Zoobot/Galaxy Zoo or the three standard arm classes. △ Less

Submitted 12 June, 2026; originally announced June 2026.

Comments: ApJ, accepted; 28 pages, 9 figures

Gaming the Answer Matcher: Examining the Impact of Text Manipulation on Automated Judgment

Authors: Manas Khatore, Sumana Sridharan, Kevork Sulahian, Benjamin J. Smith, Shi Feng

Abstract: Automated answer matching, which leverages LLMs to evaluate free-text responses by comparing them to a reference answer, shows substantial promise as a scalable and aligned alternative to human evaluation. However, its reliability requires robustness against strategic attacks such as guesswork or verbosity that may artificially inflate scores without improving actual correctness. In this work, we… ▽ More Automated answer matching, which leverages LLMs to evaluate free-text responses by comparing them to a reference answer, shows substantial promise as a scalable and aligned alternative to human evaluation. However, its reliability requires robustness against strategic attacks such as guesswork or verbosity that may artificially inflate scores without improving actual correctness. In this work, we systematically investigate whether such tactics deceive answer matching models by prompting examinee models to: (1) generate verbose responses, (2) provide multiple answers when unconfident, and (3) embed conflicting answers with the correct answer near the start of their response. Our results show that these manipulations do not increase scores and often reduce them. Additionally, binary scoring (which requires a matcher to answer with a definitive "correct" or "incorrect") is more robust to attacks than continuous scoring (which requires a matcher to determine partial correctness). These findings show that answer matching is generally robust to inexpensive text manipulation and is a viable alternative to traditional LLM-as-a-judge or human evaluation when reference answers are available. △ Less

Submitted 22 December, 2025; originally announced January 2026.

Comments: Accepted to the AAAI 2026 Workshop on AI Governance (AIGOV)

Inferring Relative Consequences of Mechanical Ventilation from Observational Data Using Game-Based Comparisons

Authors: David J. Albers, Tell D. Bennett, Jana de Wiljes, George Hripcsak, Bradford J. Smith, Peter D. Sottile, J. N. Stroh

Abstract: Identifying the effects of mechanical ventilation (MV) protocols in critical care requires analyzing data from heterogeneous patient-ventilator systems in the clinical decision-making environment. Multiscale interactions among these coupled components generate a high-dimensional state space that remains sparsely sampled despite extensive data collection. Analysis of existing data is essential for… ▽ More Identifying the effects of mechanical ventilation (MV) protocols in critical care requires analyzing data from heterogeneous patient-ventilator systems in the clinical decision-making environment. Multiscale interactions among these coupled components generate a high-dimensional state space that remains sparsely sampled despite extensive data collection. Analysis of existing data is essential for understanding current respiratory management practices and generating testable hypotheses about improvement. The scale and complexity of available data motivate the use of reinforcement learning (RL) to explore data-consistent counterfactual trajectories. However, formulating RL in practical applications requires a spatiotemporally dependent reward process that defines state-to-consequence relationships, their context dependence, and the delays over which consequences emerge. These poorly understood elements are not known \emph{a priori} and inferred from data via hypotheses. To that end, categorized observed states are contrasted according to their relative consequences by solving a game-based inverse problem that identifies a comparison model required for downstream probabilistic and stochastic methods such as reinforcement learning for seeking MV optimization and personalization. The inverted-game inference is validated on synthetic data to reveal potential caveats before proceeding to real-world ICU data applications that expose complexities of the data-generating process. Clinical data applications revealed that both breath-type consequences and their relative ordering are inherently context- and time-dependent, varying across patient subgroups, time, and comparison quantities, and effect timescale. The discussion includes potential developments toward a state transition model for simulating the effects of MV management actions using empirical data and game-inferred comparisons. △ Less

Submitted 4 August, 2026; v1 submitted 16 October, 2025; originally announced October 2025.

High-fidelity, quasi-deterministic entanglement generation using phase-matched spectral islands in a zero-added-loss multiplexing architecture

Authors: Jeffrey H. Shapiro, Clark Embleton, Michael G. Raymer, Brian J. Smith

Abstract: Spontaneous parametric down-converters (SPDCs) are the best available entanglement sources for distributing entanglement in a quantum internet. However, their intrinsically probabilistic nature, and their need to operate at low brightness to suppress multipair events, dictate that multiplexed SPDC arrays are required for high-rate distribution in that application. Early SPDC multiplexing proposals… ▽ More Spontaneous parametric down-converters (SPDCs) are the best available entanglement sources for distributing entanglement in a quantum internet. However, their intrinsically probabilistic nature, and their need to operate at low brightness to suppress multipair events, dictate that multiplexed SPDC arrays are required for high-rate distribution in that application. Early SPDC multiplexing proposals involved path switching, whose switching losses significantly degrade performance. The present paper proposes and analyzes a scheme for spectral multiplexing that provides entanglement-distribution rates well in excess of the state of the art. It builds on zero-added-loss multiplexing (ZALM)~[Phys. Rev. Appl. {\bf 19}, 054029 (2023)] for high-rate heralded entanglement generation, which does not require a switched array of SPDCs. Our ZALM's SPDCs rely on nonlinear crystals with $N_I$ phase-matched spectral islands, each generating two-mode squeezed-vacuum states. Also, our ZALM's multiplexing protocol uses both same-island and cross-island heralding, which allows the entanglement-delivery rate to approximately scale as $N_I^2$ in the realistic weak-squeezing regime. As a result, our scheme uses an order of magnitude fewer spectral channels than the original ZALM proposal, which may enable near-term implementations of satellite-to-ground or fiber-optic based ZALM architectures. △ Less

Submitted 9 October, 2025; v1 submitted 18 July, 2025; originally announced July 2025.

Comments: 18 pages, 10 figures, 1 table, additional derivation details added

The Complex Multi-Wavelength Morphology of the Peculiar Compact Galaxy Group IC 2431

Authors: Beverly J. Smith, Roberto Soria, Douglas Swartz, Mark L. Giroux, Curtis Struck, Ryan Urquhart

Abstract: We present new Chandra X-ray imaging spectroscopy of the compact galaxy group IC 2431, and compare with archival ultraviolet, optical, infrared, and radio images. IC 2431 is a starburst system containing three tidally-distorted disk galaxies. All three galaxies may have active nuclei. One galaxy is classified as an AGN based on its optical spectrum, a second is identified as a possible X-ray AGN b… ▽ More We present new Chandra X-ray imaging spectroscopy of the compact galaxy group IC 2431, and compare with archival ultraviolet, optical, infrared, and radio images. IC 2431 is a starburst system containing three tidally-distorted disk galaxies. All three galaxies may have active nuclei. One galaxy is classified as an AGN based on its optical spectrum, a second is identified as a possible X-ray AGN based on the Chandra data, and the third galaxy may host a radio AGN. In optical images, a prominent dust lane crosses the southern galaxy, while Spitzer infrared images show a dusty bridge connecting the two brightest galaxies. Chandra maps reveal a massive (2 x 10^7 M(sun)) concentration of hot gas between these two galaxies, as well as several other knots of hot gas and non-thermal emission. The unabsorbed X-ray luminosity of the hot gas in IC 2431 is ~ 1 x 10^42 erg/s, which is enhanced by about a factor of four relative to the star formation rate, compared to other star-forming galaxies. In radio maps, a bright jet/ridge of radio continuum emission extends 4 kpc from one nucleus. We compare the properties of IC 2431 with those of other interacting galaxy systems, and discuss two different scenarios that may account for the peculiarities of IC 2431: ram pressure stripping of the interstellar medium during a head-on collision between two galaxies, or an AGN-powered radio jet that has been distorted by an interaction with interstellar gas during a tidal encounter between galaxies. △ Less

Submitted 14 July, 2025; originally announced July 2025.

Comments: 41 pages; accepted by ApJ

Entanglement source and quantum memory analysis for zero added-loss multiplexing

Authors: Jeffrey H. Shapiro, Michael G. Raymer, Clark Embleton, Franco N. C. Wong, Brian J. Smith

Abstract: High-rate, high-fidelity entanglement distribution is essential to the creation of a quantum internet, but recent achievements in fiber and satellite-based entanglement distribution fall far short of what is needed. Chen et al. [Phys. Rev. Appl. 19, 054209 (2023)] proposed a means for dramatically increasing entanglement-distribution rates via zero added-loss multiplexing (ZALM). ZALM's quantum tr… ▽ More High-rate, high-fidelity entanglement distribution is essential to the creation of a quantum internet, but recent achievements in fiber and satellite-based entanglement distribution fall far short of what is needed. Chen et al. [Phys. Rev. Appl. 19, 054209 (2023)] proposed a means for dramatically increasing entanglement-distribution rates via zero added-loss multiplexing (ZALM). ZALM's quantum transmitter employs a pair of Sagnac-configured spontaneous parametric downconverters (SPDCs), channelization via dense wavelength-division multiplexing (DWDM) filtering, and partial Bell-state measurements (BSMs) to realize a heralded source of frequency-multiplexed polarization-entangled biphotons. Each biphoton is transmitted to Alice and Bob with a classical message identifying its frequency channel and the heralded entangled state. Their quantum receivers use DWDM filtering and mode conversion to interface their received biphotons to intra-cavity color-center quantum memories. This paper delves deeply into ZALM's SPDCs, partial-BSMs, and loading of Alice and Bob's quantum memories. It derives the density operators for the SPDC sources and the quantum memories, allowing heralding probability, heralding efficiency, and fidelity to be evaluated for both the polarization-entangled biphotons and the loaded quantum memories, thus enabling exploration of the parameter space for optimizing ZALM performance. Even without optimization analysis, the paper already demonstrates two critical features of the ZALM architecture: the necessity of achieving a near-separable channelized biphoton wave function to ensure the biphoton sent to Alice and Bob is of high purity; and the premium placed on Alice and Bob's temporal-mode converters' enabling narrowband push-pull memory loading to ensure the arriving biphoton's state is faithfully transferred to the intra-cavity color centers. △ Less

Submitted 26 September, 2024; v1 submitted 19 June, 2024; originally announced June 2024.

Comments: 26 pages, 15 figure, 1 table

Detection and characterization of detached tidal dwarf galaxies

Authors: Javier Zaragoza-Cardiel, Beverly J. Smith, Mark G. Jones, Mark L. Giroux, Shawn Toner, Jairo A. Alzate, David Fernández-Arenas, Yalia D. Mayya, Gisela Ortiz-León, Mauricio Portilla

Abstract: Tidal interactions between galaxies often give rise to tidal tails, which can harbor concentrations of stars and interstellar gas resembling dwarf galaxies. Some of these tidal dwarf galaxies (TDGs) have the potential to detach from their parent galaxies and become independent entities, but their long-term survival is uncertain. In this study, we conducted a search for detached TDGs associated wit… ▽ More Tidal interactions between galaxies often give rise to tidal tails, which can harbor concentrations of stars and interstellar gas resembling dwarf galaxies. Some of these tidal dwarf galaxies (TDGs) have the potential to detach from their parent galaxies and become independent entities, but their long-term survival is uncertain. In this study, we conducted a search for detached TDGs associated with a sample of 39 interacting galaxy pairs in the local Universe using infrared, ultraviolet, and optical images. We employed IR colors and UV/optical/IR spectral energy distributions to identify potential interlopers, such as foreground stars or background quasars. Through spectroscopic observations using the Boller and Chivens spectrograph at San Pedro Mártir Observatory, we confirmed that six candidate TDGs are at the same redshift as their putative parent galaxy pairs. We identified and measured emission lines in the optical spectra and calculated nebular oxygen abundances, which range from log(O/H) = 8.10 $\pm$ 0.01 to 8.51 $\pm$ 0.02. We have serendipitously discovered an additional detached TDG candidate in Arp72 using available spectra from SDSS. Utilizing the photometric data and the CIGALE code for stellar population and dust emission fitting, we derived the stellar masses, stellar population ages, and stellar metallicities for these detached TDGs. Compared to standard mass-metallicity relations for dwarf galaxies, five of the seven candidates have higher than expected metallicities, confirming their tidal origins. One of the seven candidates remains unclear due to large uncertainties in metallicity, and another has stellar and nebular metallicities compatible with those of a preexisting dwarf galaxy. The latter object is relatively compact in the optical relative to its stellar mass, in contrast to the other candidate TDGs [abridged]. △ Less

Submitted 27 June, 2024; v1 submitted 7 June, 2024; originally announced June 2024.

Comments: Accepted for publication in Astronomy and Astrophysics. 15 pages, 9 figures, 6 tables

Journal ref: A&A 689, A206 (2024)

Grand Design vs. Multi-Armed Spiral Galaxies: Dependence on Galaxy Structure

Authors: Beverly J. Smith, Matthew Watson, Mark L. Giroux, Curtis Struck

Abstract: We developed an algorithm to use Galaxy Zoo 3D spiral arm masks produced by citizen scientist volunteers to semi-automatically classify spiral galaxies as either multi-armed or grand design spirals. Our final sample consists of 299 multi-armed and 245 grand design galaxies. On average, the grand design galaxies have smaller stellar masses than the multi-armed galaxies. For a given stellar mass, th… ▽ More We developed an algorithm to use Galaxy Zoo 3D spiral arm masks produced by citizen scientist volunteers to semi-automatically classify spiral galaxies as either multi-armed or grand design spirals. Our final sample consists of 299 multi-armed and 245 grand design galaxies. On average, the grand design galaxies have smaller stellar masses than the multi-armed galaxies. For a given stellar mass, the grand design galaxies have larger concentrations, earlier Hubble types, smaller half-light radii, and larger central surface mass densities than the multi-armed galaxies. Lower mass galaxies of both arm classes have later Hubble types and lower concentrations than higher mass galaxies. In our sample, a higher fraction of grand design galaxies have classical bulges rather than pseudo-bulges, compared to multi-armed galaxies. These results are consistent with theoretical models and simulations which suggest that dense classical bulges support the development and/or longevity of 2-armed spiral patterns. Similar specific star formation rates are found in multi-armed and grand design galaxies with similar stellar masses and concentrations. This implies that the specific star formation rates in spiral galaxies is a function of concentration and stellar mass, but independent of the number of spiral arms. Our classifications are consistent with arm counts from the Galaxy Zoo 2 project and published m=3 Fourier amplitudes. △ Less

Submitted 2 May, 2024; originally announced May 2024.

Comments: Astronomical Journal, in press, 31 pages, 17 figures

Limitations in Fluorescence-Detected Entangled Two-Photon-Absorption Experiments: Exploring the Low- to High-Gain Squeezing Regimes

Authors: Tiemo Landes, Brian J. Smith, Michael G. Raymer

Abstract: We closely replicated and extended a recent experiment ("Spatial properties of entangled two-photon absorption," Phys. Rev. Lett. 129, 183601, 2022) that reportedly observed enhancement of two-photon absorption rates in molecular samples by using time-frequency-entangled photon pairs, and we found that in the low-flux regime, where such enhancement is theoretically predicted in-principle, the two-… ▽ More We closely replicated and extended a recent experiment ("Spatial properties of entangled two-photon absorption," Phys. Rev. Lett. 129, 183601, 2022) that reportedly observed enhancement of two-photon absorption rates in molecular samples by using time-frequency-entangled photon pairs, and we found that in the low-flux regime, where such enhancement is theoretically predicted in-principle, the two-photon fluorescence signal is below detection threshold using current state-of-the-art methods. The results are important in the context of efforts to enable quantum-enhanced molecular spectroscopy and imaging at ultra-low optical flux. Using an optical parametric down-conversion photon-pair source that can be varied from the low-gain spontaneous regime to the high-gain squeezing regime, we observed two-photon-induced fluorescence in the high-gain regime but in the low-gain regime any fluorescence was below detection threshold. We supplemented the molecular fluorescence experiments with a study of nonlinear-optical sum-frequency generation, for which we are able to observe the low-to-high-gain crossover, thereby verifying our theoretical models and experimental techniques. The observed rates (or lack thereof) in both experiments are consistent with theoretical predictions and with our previous experiments, and indicate that time-frequency photon entanglement does not provide a practical means to enhance in-solution molecular two-photon fluorescence spectroscopy or imaging with current techniques. △ Less

Submitted 25 April, 2024; originally announced April 2024.

Maximum-Likelihood Estimation of Glandular Fraction for Mammography and its Effect on Microcalcification Detection

Authors: Bryce J. Smith, Joyoni Dey, Lacey Medlock, David Solis, Krystal Kirby

Abstract: Objective: Breast tissue is mainly a mixture of adipose and fibro-glandular tissue. Cancer risk and risk of undetected breast cancer increases with the amount of glandular tissue in the breast. Therefore, radiologists must report the total volume glandular fraction or a BI-RADS classification in screening and diagnostic mammography. A Maximum Likelihood algorithm is shown to estimate the pixel-wis… ▽ More Objective: Breast tissue is mainly a mixture of adipose and fibro-glandular tissue. Cancer risk and risk of undetected breast cancer increases with the amount of glandular tissue in the breast. Therefore, radiologists must report the total volume glandular fraction or a BI-RADS classification in screening and diagnostic mammography. A Maximum Likelihood algorithm is shown to estimate the pixel-wise glandular fraction from mammographic images. The pixel-wise glandular fraction provides information that helps localize dense tissue. The total volume glandular fraction can be calculated from pixel-wise glandular fraction. The algorithm was implemented for images acquired with an anti-scatter grid, and without using the anti-scatter grid but followed by software scatter removal. The work also studied if presenting the pixel-wise glandular fraction image alongside the usual mammographic image has the potential to improve the contrast-to-noise ratio on micro-calcifications in the breast. Results: For the TOPAS simulated images, the glandular fraction was estimated with a root mean squared error of 3.2% and 2.5% for the without and with anti-scatter grid cases. Average absolute errors were (3.7 +/- 2.4)% and (3.6 +/- 0.9)%, respectively. Results from DICOM clinical images (where the true glandular fraction is unknown) show that the algorithm gives a glandular fraction within the average range expected from the literature. For microcalcification detection, the contrast-to-noise ratio improved by 17.5-548% in DICOM images and 5.1-88% in TOPAS images. Conclusion: We show a method of accurate estimation of pixel-wise glandular fraction image, providing localization information of breast density. The glandular fraction images also showed an improvement in contrast to noise ratio for detecting microcalcifications, a risk factor in breast cancer. △ Less

Submitted 10 October, 2023; v1 submitted 18 April, 2023; originally announced April 2023.

Comments: Pre-print

Interferometric imaging using shared quantum entanglement

Authors: Matthew R. Brown, Markus Allgaier, Valérian Thiel, John D. Monnier, Michael G. Raymer, Brian J. Smith

Abstract: Quantum entanglement-based imaging promises significantly increased resolution by extending the spatial separation of optical collection apertures used in very-long-baseline interferometry for astronomy and geodesy. We report a table-top entanglement-based interferometric imaging technique that utilizes two entangled field modes serving as a phase reference between two apertures. The spatial distr… ▽ More Quantum entanglement-based imaging promises significantly increased resolution by extending the spatial separation of optical collection apertures used in very-long-baseline interferometry for astronomy and geodesy. We report a table-top entanglement-based interferometric imaging technique that utilizes two entangled field modes serving as a phase reference between two apertures. The spatial distribution of a simulated thermal light source is determined by interfering light collected at each aperture with one of the entangled fields and performing joint measurements. This experiment demonstrates the ability of entanglement to implement interferometric imaging. △ Less

Submitted 21 September, 2023; v1 submitted 14 December, 2022; originally announced December 2022.

The Effect of Environment on Galaxy Spiral Arms, Bars, Concentration, and Quenching

Authors: Beverly J. Smith, Mark L. Giroux, Curtis Struck

Abstract: For a sample of 4378 nearby spiral and S0 galaxies, Yu and Ho (2020) used Fourier analysis of Sloan Digital Sky Survey images to show that the strengths of the spiral arms and the pitch angles of the arms are inversely correlated with central concentration. In the current study, we search for trends in the Yu and Ho (2020) spiral arm parameters with environment and specific star formation rate (sS… ▽ More For a sample of 4378 nearby spiral and S0 galaxies, Yu and Ho (2020) used Fourier analysis of Sloan Digital Sky Survey images to show that the strengths of the spiral arms and the pitch angles of the arms are inversely correlated with central concentration. In the current study, we search for trends in the Yu and Ho (2020) spiral arm parameters with environment and specific star formation rate (sSFR). When comparing galaxies with similar concentrations, we do not find a significant difference in the arm strengths or pitch angles of spiral galaxies in clusters compared to field galaxies. When differences in concentration are taken into account, we also find no significant difference in the parameter f3 for cluster spirals compared to field spirals, where f3 is the normalized m = 3 Fourier amplitude. When concentration is held fixed, both arm strength and pitch angle are correlated with sSFR, but f3 is not. These relations support the suggestion by Davis et al. (2015) of a `fundamental plane' of spiral structure involving pitch angle, bulge stellar mass, and gas surface density. We discuss these results in terms of theories of spiral arm production and quenching in galaxies. To aid comparison with earlier studies based on Galaxy Zoo, we explore how the Yu and Ho (2020) parameters relate to similar parameters measured by Galaxy Zoo (i.e., f3 vs. number of arms, pitch angle vs. winding parameter, and concentration vs. bulge class). △ Less

Submitted 11 August, 2022; originally announced August 2022.

Comments: AJ, in press

Improving performance in multi-objective decision-making in Bottles environments with soft maximin approaches

Authors: Benjamin J Smith, Robert Klassert, Roland Pihlakas

Abstract: Balancing multiple competing and conflicting objectives is an essential task for any artificial intelligence tasked with satisfying human values or preferences. Conflict arises both from misalignment between individuals with competing values, but also between conflicting value systems held by a single human. Starting with principle of loss-aversion, we designed a set of soft maximin function appro… ▽ More Balancing multiple competing and conflicting objectives is an essential task for any artificial intelligence tasked with satisfying human values or preferences. Conflict arises both from misalignment between individuals with competing values, but also between conflicting value systems held by a single human. Starting with principle of loss-aversion, we designed a set of soft maximin function approaches to multi-objective decision-making. Bench-marking these functions in a set of previously-developed environments, we found that one new approach in particular, 'split-function exp-log loss aversion' (SFELLA), learns faster than the state of the art thresholded alignment objective method (Vamplew et al, 2021) on three of four tasks it was tested on, and achieved the same optimal performance after learning. SFELLA also showed relative robustness improvements against changes in objective scale, which may highlight an advantage dealing with distribution shifts in the environment dynamics. Due to publishing rules, further work could not be presented in the preprint, but in the final published version, we will further compare SFELLA to the multi-objective reward exponentials (MORE) approach (Rolf, 2020), demonstrating that SFELLA performs similarly to MORE in a simple previously-described foraging task, but in a modified foraging environment with a new resource that was not depleted as the agent worked, SFELLA collected more of the new resource with very little cost incurred in terms of the old resource. Overall, we found SFELLA useful for avoiding problems that sometimes occur with a thresholded approach, and more reward-responsive than MORE while retaining its conservative, loss-averse incentive structure. △ Less

Submitted 11 August, 2022; v1 submitted 8 August, 2022; originally announced August 2022.

Smartphone-based measurements of the optical properties of snow

Authors: Markus Allgaier, Brian J. Smith

Abstract: Snow is a highly complex medium composed of ice crystals of various shapes and sizes. Knowledge of its intrinsic optical properties such as the scattering and absorption coefficient is tantamount to radiative transfer models in climate research. The absorption coefficient, in particular, allows us to access information about light-absorbing particles contained in the snow. In contrast to snow's ap… ▽ More Snow is a highly complex medium composed of ice crystals of various shapes and sizes. Knowledge of its intrinsic optical properties such as the scattering and absorption coefficient is tantamount to radiative transfer models in climate research. The absorption coefficient, in particular, allows us to access information about light-absorbing particles contained in the snow. In contrast to snow's apparent properties like the albedo, measuring the intrinsic properties is challenging. Here, we present a simple apparatus that can measure bulk optical properties of snow using readily available components and a smartphone camera, and a robust diffuse-optical framework for data analysis. We demonstrate the instrument both on scattering phantoms with known scattering and absorption coefficient as well as in the field. Its low cost, simplicity and portability uniquely qualify this setup for large-scale field work, undergraduate education and citizen science. △ Less

Submitted 13 May, 2022; v1 submitted 11 April, 2022; originally announced April 2022.

Journal ref: Appl. Opt. 61, 4429-4436 (2022)

Direct measurement of optical properties of glacier ice using a photon-counting diffuse LiDAR

Authors: Markus Allgaier, Matthew G. Cooper, Anders E. Carlson, Sarah W. Cooley, Jonathan C. Ryan, Brian J. Smith

Abstract: The production of meltwater from glacier ice, which is exposed at the margins of land ice during the summer, is responsible for a large proportion of glacier mass loss. The rate of meltwater production from glacier ice is especially sensitive to its physical structure and chemical composition which combine to determine the albedo of glacier ice. However, the optical properties of near-surface glac… ▽ More The production of meltwater from glacier ice, which is exposed at the margins of land ice during the summer, is responsible for a large proportion of glacier mass loss. The rate of meltwater production from glacier ice is especially sensitive to its physical structure and chemical composition which combine to determine the albedo of glacier ice. However, the optical properties of near-surface glacier ice are not well known since most prior work has focused on ice made in the laboratory or from deep cores. Here, we demonstrate a measurement technique based on diffuse propagation of nanosecond-duration laser pulses in near-surface glacier ice that enables the independent measurement of the scattering and absorption coefficients, allowing for a complete description of the processes governing radiative transfer. We employ a photon-counting detector to overcome the high losses associated with diffuse optics. The instrument is highly portable and rugged, making it optimally suited for deployment in remote regions. A set of measurements taken on Collier Glacier, Oregon, serves as a demonstration of the technique. These measurements provide insight into both physical structure and composition of near-surface glacier ice and open new avenues for the analysis of light-absorbing impurities and remote sensing of the cryosphere. △ Less

Submitted 24 February, 2022; v1 submitted 19 January, 2022; originally announced January 2022.

Scalar reward is not enough: A response to Silver, Singh, Precup and Sutton (2021)

Authors: Peter Vamplew, Benjamin J. Smith, Johan Kallstrom, Gabriel Ramos, Roxana Radulescu, Diederik M. Roijers, Conor F. Hayes, Fredrik Heintz, Patrick Mannion, Pieter J. K. Libin, Richard Dazeley, Cameron Foale

Abstract: The recent paper `"Reward is Enough" by Silver, Singh, Precup and Sutton posits that the concept of reward maximisation is sufficient to underpin all intelligence, both natural and artificial. We contest the underlying assumption of Silver et al. that such reward can be scalar-valued. In this paper we explain why scalar rewards are insufficient to account for some aspects of both biological and co… ▽ More The recent paper `"Reward is Enough" by Silver, Singh, Precup and Sutton posits that the concept of reward maximisation is sufficient to underpin all intelligence, both natural and artificial. We contest the underlying assumption of Silver et al. that such reward can be scalar-valued. In this paper we explain why scalar rewards are insufficient to account for some aspects of both biological and computational intelligence, and argue in favour of explicitly multi-objective models of reward maximisation. Furthermore, we contend that even if scalar reward functions can trigger intelligent behaviour in specific cases, it is still undesirable to use this approach for the development of artificial general intelligence due to unacceptable risks of unsafe or unethical behaviour. △ Less

Submitted 24 November, 2021; originally announced December 2021.

Quantum-enhanced interferometry by entanglement-assisted rejection of environmental noise

Authors: Alex O. C. Davis, Giacomo Sorelli, Valerian Thiel, Brian J. Smith

Abstract: Sensing and measurement tasks in severely adverse conditions such as loss, noise and dephasing can be improved by illumination with quantum states of light. Previous results have shown a modest reduction in the number of measurements necessary to achieve a given precision. Here, we compare three illumination strategies for estimating the relative phase in a noisy, lossy interferometer. When includ… ▽ More Sensing and measurement tasks in severely adverse conditions such as loss, noise and dephasing can be improved by illumination with quantum states of light. Previous results have shown a modest reduction in the number of measurements necessary to achieve a given precision. Here, we compare three illumination strategies for estimating the relative phase in a noisy, lossy interferometer. When including a common phase fluctuation in the noise processes, we show that using an entangled probe achieves an advantage in parameter estimation precision that scales with the number of entangled modes. This work provides a theoretical foundation for the use of highly multimode entangled states of light for practical measurement tasks in experimentally challenging conditions. △ Less

Submitted 14 October, 2021; originally announced October 2021.

Comments: 2 figures 3 appendices

Spectrally-resolved four-photon interference of time-frequency entangled photons

Authors: Sofiane Merkouche, Valérian Thiel, Brian J. Smith

Abstract: Pairs of photons entangled in their time-frequency degree of freedom are of great interest in quantum optics research and applications, due to their relative ease of generation and their high capacity for encoding information. Here we analyze, both theoretically and experimentally, the behavior of phase-insensitive spectrally-resolved interferences arising from two pairs of time-frequency entangle… ▽ More Pairs of photons entangled in their time-frequency degree of freedom are of great interest in quantum optics research and applications, due to their relative ease of generation and their high capacity for encoding information. Here we analyze, both theoretically and experimentally, the behavior of phase-insensitive spectrally-resolved interferences arising from two pairs of time-frequency entangled photons. At its core, this is a multimode entanglement swapping experiment, whereby a spectrally resolved joint measurement on the idler photons from both pairs results in projecting the signal photons onto a Bell state whose form depends on the measurement outcome. Our analysis is a thorough exploration of what can be achieved using time-frequency entanglement and spectrally-resolved Bell-state measurements. △ Less

Submitted 12 April, 2021; originally announced April 2021.

Comments: arXiv admin note: text overlap with arXiv:2102.03485

Diffuse optics for glaciology

Authors: Markus Allgaier, Brian J. Smith

Abstract: Optical probing of glaciers has the potential for tremendous impact on environmental science. However, glacier ice is turbid, which prohibits the use of most established optical measurements for determining a glacier's interior structure. Here, we propose a method for determining the depth, scattering and absorption length based upon diffuse propagation of short optical pulses. Our model allows us… ▽ More Optical probing of glaciers has the potential for tremendous impact on environmental science. However, glacier ice is turbid, which prohibits the use of most established optical measurements for determining a glacier's interior structure. Here, we propose a method for determining the depth, scattering and absorption length based upon diffuse propagation of short optical pulses. Our model allows us to extract several characteristics of the glacier. Performing Monte Carlo simulations implementing Mie scattering and mixed boundary conditions, we show that the proposed approach should be feasible with current technology. The results suggest that optical properties and geometry of the glacier can be extracted from realistic measurements, which could be implemented with low cost and small footprint. △ Less

Submitted 22 May, 2021; v1 submitted 19 March, 2021; originally announced March 2021.

Quantifying the enhancement of two-photon absorption due to spectral-temporal entanglement

Authors: Tiemo Landes, Michael G. Raymer, Markus Allgaier, Sofiane Merkouche, Brian J. Smith, Andrew H. Marcus

Abstract: When a low flux of time-frequency-entangled photon pairs (EPP) illuminates a two-photon transition, the rate of two-photon absorption (TPA) can be enhanced considerably by the quantum nature of photon number correlations and frequency correlations. We present a quantum-theoretic derivation of entangled TPA (ETPA) and calculate an upper bound on the amount of quantum enhancement that is possible in… ▽ More When a low flux of time-frequency-entangled photon pairs (EPP) illuminates a two-photon transition, the rate of two-photon absorption (TPA) can be enhanced considerably by the quantum nature of photon number correlations and frequency correlations. We present a quantum-theoretic derivation of entangled TPA (ETPA) and calculate an upper bound on the amount of quantum enhancement that is possible in such systems. The derived bounds indicate that in order to observe ETPA the experiments would need to operate at a combination of significantly higher rates of EPP illumination, molecular concentrations, and conventional TPA cross sections than are achieved in typical experiments. △ Less

Submitted 18 March, 2021; originally announced March 2021.

Comments: 14 pages, 2 figures, submitted for publication

Heralding multiple photonic pulsed Bell-pairs via frequency-resolved entanglement swapping

Authors: Sofiane Merkouche, Valérian Thiel, Alex O. C. Davis, Brian J. Smith

Abstract: Entanglement is a unique property of quantum systems and an essential resource for many quantum technologies. The ability to transfer or swap entanglement between systems is an important protocol in quantum information science. Entanglement between photons forms the basis of distributed quantum networks and the demonstration of photonic entanglement swapping is essential for their realization. Her… ▽ More Entanglement is a unique property of quantum systems and an essential resource for many quantum technologies. The ability to transfer or swap entanglement between systems is an important protocol in quantum information science. Entanglement between photons forms the basis of distributed quantum networks and the demonstration of photonic entanglement swapping is essential for their realization. Here an experiment demonstrating entanglement swapping from two independent multimode time-frequency entangled sources is presented, resulting in multiple heralded temporal-mode Bell states. Entanglement in the heralded states is verified by measuring conditional anti-correlated joint spectra as well as quantum beating in two-photon interference. Our proof-of-concept experiment is able to distinguish up to five orthogonal Bell pairs within the same setup, limited in principle only by the entanglement of the sources. △ Less

Submitted 5 February, 2021; originally announced February 2021.

A positive operator-valued measure for two-photon detection via sum-frequency generation

Authors: Sofiane Merkouche, Valérian Thiel, Brian J. Smith

Abstract: Spontaneous parametric down conversion (PDC), in the perturbative limit, can be considered as a probabilistic splitting of one input photon into two output photons. Conversely, sum-frequency generation (SFG) implements the reverse process of combining two input photons into one. Here we show that a single-photon projective measurement in the temporal-mode basis of the output photon of a two-photon… ▽ More Spontaneous parametric down conversion (PDC), in the perturbative limit, can be considered as a probabilistic splitting of one input photon into two output photons. Conversely, sum-frequency generation (SFG) implements the reverse process of combining two input photons into one. Here we show that a single-photon projective measurement in the temporal-mode basis of the output photon of a two-photon SFG process effects a generalized measurement on the input two-photon state. We describe the positive-operator-valued measure (POVM) associated with such a measurement, and show that its elements are proportional to the two-photon states produced by the time-reversed PDC process. Such a detection acts as a joint measurement on two photons, and is thus an important component of many quantum information processing protocols relying on photonic entanglement. Using the retrodictive approach, we analyze the properties of the two-photon POVM that are relevant for quantum protocols exploiting two-photon states and measurements. △ Less

Submitted 29 March, 2021; v1 submitted 15 January, 2021; originally announced January 2021.

Comments: 11 pages, 5 figures

Journal ref: Phys. Rev. A 103, 043711 (2021)

Experimental feasibility of molecular two-photon absorption with isolated time-frequency-entangled photon pairs

Authors: Tiemo Landes, Markus Allgaier, Sofiane Merkouche, Brian J. Smith, Andrew H. Marcus, Michael G. Raymer

Abstract: Entangled photon pairs have been promised to deliver a substantial quantum advantage for two-photon absorption spectroscopy. However, recent work has challenged the previously reported magnitude of quantum enhancement in two-photon absorption. Here, we present an experimental comparison of sum-frequency generation and molecular absorption, each driven by isolated photon pairs. We establish an uppe… ▽ More Entangled photon pairs have been promised to deliver a substantial quantum advantage for two-photon absorption spectroscopy. However, recent work has challenged the previously reported magnitude of quantum enhancement in two-photon absorption. Here, we present an experimental comparison of sum-frequency generation and molecular absorption, each driven by isolated photon pairs. We establish an upper bound on the enhancement for entangled-two-photon absorption in Rhodamine-6G, which lies well below previously reported values. △ Less

Submitted 12 December, 2020; originally announced December 2020.

Journal ref: Phys. Rev. Research 3, 033154 (2021)

Two-photon absorption of time-frequency-entangled photon pairs by molecules: the roles of photon-number correlations and spectral correlations

Authors: Michael G. Raymer, Tiemo Landes, Markus Allgaier, Sofiane Merkouche, Brian J. Smith, Andrew H. Marcus

Abstract: While two-photon absorption (TPA) and other forms of nonlinear interactions of molecules with isolated time-frequency-entangled photon pairs (EPP) have been predicted to display a variety of fascinating effects, their potential use in practical quantum-enhanced molecular spectroscopy requires close examination. This paper presents a detailed theoretical study of quantum-enhanced TPA by both photon… ▽ More While two-photon absorption (TPA) and other forms of nonlinear interactions of molecules with isolated time-frequency-entangled photon pairs (EPP) have been predicted to display a variety of fascinating effects, their potential use in practical quantum-enhanced molecular spectroscopy requires close examination. This paper presents a detailed theoretical study of quantum-enhanced TPA by both photon-number correlations and spectral correlations, including an account of the deleterious effects of dispersion. While such correlations in EPP created by spontaneous parametric down conversion can increase the TPA rate significantly in the regime of extremely low optical flux, we find that for typical molecules in solution this regime corresponds to such low TPA event rates as to be unobservable in practice. Our results support the usefulness of EPP spectroscopy in atomic or other narrow-linewidth systems, while questioning the efficacy of such approaches for broadband systems including molecules in solution. △ Less

Submitted 9 December, 2020; originally announced December 2020.

Comments: 38 pages, 4 figures

A damaged-informed lung model for ventilator waveforms

Authors: Deepak. K. Agrawal, Bradford J. Smith, Peter D. Sottile, David J. Albers

Abstract: The acute respiratory distress syndrome (ARDS) is characterized by the acute development of diffuse alveolar damage (DAD) resulting in increased vascular permeability and decreased alveolar gas exchange. Mechanical ventilation is a potentially lifesaving intervention to improve oxygen exchange but has the potential to cause ventilator-induced lung injury (VILI). A general strategy to reduce VILI i… ▽ More The acute respiratory distress syndrome (ARDS) is characterized by the acute development of diffuse alveolar damage (DAD) resulting in increased vascular permeability and decreased alveolar gas exchange. Mechanical ventilation is a potentially lifesaving intervention to improve oxygen exchange but has the potential to cause ventilator-induced lung injury (VILI). A general strategy to reduce VILI is to use low tidal volume and low-pressure ventilation, but optimal ventilator settings for an individual patient are difficult for the bedside physician to determine and mortality from ARDS remains unacceptably high. Motivated by the need to minimize VILI, scientists have developed models of varying complexity to understand diseased pulmonary physiology. However, simple models often fail to capture real-world injury while complex models tend to not be estimable with clinical data, limiting the clinical utility of existing models. To address this gap, we present a physiologically anchored data-driven model to better model lung injury. Our approach relies on using clinically relevant features in the ventilator waveform data that contain information about pulmonary physiology, patients-ventilator interaction and ventilator settings. Our lung model can reproduce essential physiology and pathophysiology dynamics of differently damaged lungs for both controlled mouse model data and uncontrolled human ICU data. The estimated parameters values that are correlated with a known measure of lung physiology agree with the observed lung damage. In future endeavors, this model could be used to phenotype ventilator waveforms and serve as a basis for predicting the course of ARDS and improving patient care. △ Less

Submitted 23 October, 2020; originally announced October 2020.

Comments: 22 pages, 7 figure, 1 table and Supplementary File

Gaussian versus non-Gaussian filtering of phase-insensitive nonclassicality

Authors: Benjamin Kühn, Werner Vogel, Valérian Thiel, Sofiane Merkouche, Brian J. Smith

Abstract: Measures of quantum properties are essential to understanding the fundamental differences between quantum and classical systems as well as quantifying resources for quantum technologies. Here two broad classes of bosonic phase-space functions, which are filtered versions of the Glauber-Sudarshan $P$ function, are compared with regard to their ability to uncover nonclassical effects of light throug… ▽ More Measures of quantum properties are essential to understanding the fundamental differences between quantum and classical systems as well as quantifying resources for quantum technologies. Here two broad classes of bosonic phase-space functions, which are filtered versions of the Glauber-Sudarshan $P$ function, are compared with regard to their ability to uncover nonclassical effects of light through their negativities. Gaussian filtering of the $P$ function yields the family of $s$-parametrized quasiprobabilities, while more powerful regularized nonclassicality quasiprobabilities are obtained by non-Gaussian filtering. A method is proposed to directly sample such phase-space functions for the restricted case of phase-independent quantum states from balanced homodyne measurements. This overcomes difficulties of previous approaches that manually append uniformly distributed optical phases to the measured quadrature data. We experimentally demonstrate this technique for heralded single- and two-photon states using balanced homodyne detection with varying efficiency. The $s$-parametrized quasiprobabilities, which can be directly sampled, are non-negative for detection efficiencies below 0.5. By contrast, we show that significant negativities of non-Gaussian filtered quasiprobabilities uncover nonclassical effects even for low efficiencies. △ Less

Submitted 9 May, 2021; v1 submitted 5 October, 2020; originally announced October 2020.

Journal ref: Phys. Rev. Lett. 126, 173603 (2021)

Temporal mode transformations by sequential time and frequency phase modulation for applications in quantum information science

Authors: James Ashby, Valerian Thiel, Markus Allgaier, Peru D'Ornellas, Alex O. C. Davis, Brian J. Smith

Abstract: Controlling the temporal mode shape of quantum light pulses has wide ranging application to quantum information science and technology. Techniques have been developed to control the bandwidth, allow shifting in the time and frequency domains, and perform mode-selective beam-splitter-like transformations. However, there is no present scheme to perform targeted multimode unitary transformations on t… ▽ More Controlling the temporal mode shape of quantum light pulses has wide ranging application to quantum information science and technology. Techniques have been developed to control the bandwidth, allow shifting in the time and frequency domains, and perform mode-selective beam-splitter-like transformations. However, there is no present scheme to perform targeted multimode unitary transformations on temporal modes. Here we present a practical approach to realize general transformations for temporal modes. We show theoretically that any unitary transformation on temporal modes can be performed using a series of phase operations in the time and frequency domains. Numerical simulations show that several key transformations on temporal modes can be performed with greater than 95% fidelity using experimentally feasible specifications. △ Less

Submitted 16 September, 2020; originally announced September 2020.

Revealing the Double Nucleus of NGC 4490

Authors: AL Lawrence, C. R. Kerton, Curtis Struck, Beverly J. Smith

Abstract: NGC 4490/85 (UGC 7651/48) or Arp 269 is well known for being one of the closest interacting/merging galactic systems. NGC 4490 has a high star formation rate (SFR) and is surrounded by an enormous HI feature stretching about 60 kpc north and south of the optically visible galaxies. Both the driver for the high SFR in NGC 4490 and the formation mechanism of the HI structure are puzzling aspects of… ▽ More NGC 4490/85 (UGC 7651/48) or Arp 269 is well known for being one of the closest interacting/merging galactic systems. NGC 4490 has a high star formation rate (SFR) and is surrounded by an enormous HI feature stretching about 60 kpc north and south of the optically visible galaxies. Both the driver for the high SFR in NGC 4490 and the formation mechanism of the HI structure are puzzling aspects of this system. We have used mid-infrared Spitzer data to show that NGC 4490 has a double nucleus morphology. One nucleus is visible in the optical, while the other is only visible at infrared and radio wavelengths. We find the optical nucleus and the potential infrared visible nucleus have similar sizes, masses, and luminosities. Both are comparable in mass and luminosity to other nuclei found in interacting galaxy pairs and much more massive and luminous compared with typical non-nuclear star-forming complexes. We examine possible origin scenarios for the infrared feature, and conclude that it is likely that NGC 4490 is itself a merger remnant, which is now interacting with NGC 4485. This earlier encounter provides both a possible driver for extended star formation in NGC 4490, and multiple pathways for the formation of the extended HI plume. △ Less

Submitted 15 January, 2020; originally announced January 2020.

Comments: 33 pages, 11 figures, 5 tables, Accepted for publication in the Astrophysical Journal

Two-color Bell states heralded via entanglement swapping

Authors: Sofiane Merkouche, Valérian Thiel, Alex O. C. Davis, Brian J. Smith

Abstract: We report on an experiment demonstrating entanglement swapping of time-frequency entangled photons. We perform a frequency-resolved Bell-state measurement on the idler photons from two independent entangled photon pairs, which projects the signal photons onto a two-color Bell state. We verify entanglement in this heralded state using two-photon interference and observing quantum beating without th… ▽ More We report on an experiment demonstrating entanglement swapping of time-frequency entangled photons. We perform a frequency-resolved Bell-state measurement on the idler photons from two independent entangled photon pairs, which projects the signal photons onto a two-color Bell state. We verify entanglement in this heralded state using two-photon interference and observing quantum beating without the use of filters, indicating the presence of two-color entanglement. Our method could lend itself to use as a highly-tunable source of frequency-bin entangled single photons. △ Less

Submitted 14 October, 2019; originally announced October 2019.

Phase-Modulated Interferometry, Spectroscopy, and Refractometry using Entangled Photon Pairs

Authors: Jonathan Lavoie, Tiemo Landes, Amr Tamimi, Brian J. Smith, Andrew H. Marcus, Michael G. Raymer

Abstract: The authors demonstrate a form of two-photon-counting interferometry by measuring the coincidence counts between single-photon-counting detectors at an output port of a Mach-Zehnder Interferometer (MZI) following injection of broad-band time-frequency-entangled photon pairs (EPP) generated from collinear spontaneous parametric down conversion into a single input port. Spectroscopy and refractometr… ▽ More The authors demonstrate a form of two-photon-counting interferometry by measuring the coincidence counts between single-photon-counting detectors at an output port of a Mach-Zehnder Interferometer (MZI) following injection of broad-band time-frequency-entangled photon pairs (EPP) generated from collinear spontaneous parametric down conversion into a single input port. Spectroscopy and refractometry are performed on a sample inserted in one internal path of the MZI by scanning the other path in length, which acquires phase and amplitude information about the samples linear response. Phase modulation and lock-in detection are introduced to increase detection signal-to-noise ratio and implement a down-sampling technique for scanning the interferometer delay, which reduces the sampling requirements needed to reproduce fully the temporal interference pattern. The phase-modulation technique also allows the contributions of various quantum-state pathways leading to the final detection outcomes to be extracted individually. Feynman diagrams frequently used in the context of molecular spectroscopy are used to describe the interferences resulting from the coherence properties of time-frequency EPPs passing through the MZI. These results are an important step toward implementation of a proposed method for molecular spectroscopy, i.e. quantum-light-enhanced two-dimensional spectroscopy. △ Less

Submitted 9 October, 2019; originally announced October 2019.

Comments: 29 pages, 17 figures, submitted for publication

Single-photon characterization by two-photon spectral interferometry

Authors: Valérian Thiel, Alex O. C. Davis, Ke Sun, Peru D'Ornellas, Xian-Min Jin, Brian J. Smith

Abstract: Single-photon sources are a fundamental resource in quantum optics. The indistinguishability and purity of photons emitted from different sources are crucial (necessary, essential) properties for many quantum applications to ensure high-visibility interference between different sources. The state of a single-photon source is described by the modes occupied by the single light quanta. Thus the abil… ▽ More Single-photon sources are a fundamental resource in quantum optics. The indistinguishability and purity of photons emitted from different sources are crucial (necessary, essential) properties for many quantum applications to ensure high-visibility interference between different sources. The state of a single-photon source is described by the modes occupied by the single light quanta. Thus the ability to determine the mode structure of a single-photon source provides a means to assess its quality, compare different sources, and provide feedback for source engineering. Here, we propose and demonstrate an experimental scheme that allows for complete characterization of the spectral-temporal state of a pulsed single-photon source. The density matrix elements of the single-photon source are determined by spectral interferometry with a known single-photon reference. Frequency-resolved coincidence measurements are performed after the unknown single-photon source is interfered with a single-photon reference pulse. Fourier analysis of the frequency-resolved two-photon interference pattern reveals the spectral-temporal density matrix of the broadband single-photon source. We present an experimental realization of this method for pure and mixed state pulsed, single-photon sources. △ Less

Submitted 30 October, 2019; v1 submitted 10 September, 2019; originally announced September 2019.

The Hot Gas Exhaust of Starburst Engines in Mergers: Testing Models of Stellar Feedback and Star Formation Regulation

Authors: Beverly J. Smith, Peter Wagstaff, Curtis Struck, Roberto Soria, Brianne Dunn, Douglas Swartz, Mark L. Giroux

Abstract: Using archival data from the Chandra X-ray telescope, we have measured the spatial extent of the hot interstellar gas in a sample of 49 nearby interacting galaxy pairs, mergers, and merger remnants. For systems with SFR > 1 M(sun)/yr, the volume and mass of hot gas are strongly and linearly correlated with the star formation rate (SFR). This supports the idea that stellar/supernovae feedback domin… ▽ More Using archival data from the Chandra X-ray telescope, we have measured the spatial extent of the hot interstellar gas in a sample of 49 nearby interacting galaxy pairs, mergers, and merger remnants. For systems with SFR > 1 M(sun)/yr, the volume and mass of hot gas are strongly and linearly correlated with the star formation rate (SFR). This supports the idea that stellar/supernovae feedback dominates the production of hot gas in these galaxies. We compared the mass of X-ray-emitting hot gas Mx(gas) with the molecular and atomic hydrogen interstellar gas masses in these galaxies (M(H2) and M(HI), respectively), using published carbon monoxide and 21 cm HI measurements. Systems with higher SFRs have larger Mx(gas)/(M(H2) + M(HI)) ratios on average, in agreement with recent numerical simulations of star formation and feedback in merging galaxies. The Mx(gas)/(M(H2) + M(HI)) ratio also increases with dust temperature on average. The ratio Mx(gas)/SFR is anti-correlated with the IRAS 60 micron to 100 micron flux ratio and with the Spitzer 3.6 micron to 24 micron. These trends may be due to variations in the spatial density of young stars, the stellar age, the ratio of young to old stars, the initial mass function, and/or the efficiency of stellar feedback. Galaxies with low SFR (<1 M(sun)/yr) and high K band luminosities may have an excess of hot gas relative to the relation for higher SFR galaxies, while galaxies with low K band luminosities (and therefore low stellar masses) may have a deficiency in hot gas, but our sample is not large enough for strong statistical significance. △ Less

Submitted 25 August, 2019; originally announced August 2019.

Comments: Astronomical Journal, in press

Pure Single Photons from Scalable Frequency Multiplexing

Authors: T. Hiemstra, T. F. Parker, P. C. Humphreys, J. Tiedau, M. Beck, M. Karpiński, B. J. Smith, A. Eckstein, W. S. Kolthammer, I. A. Walmsley

Abstract: We demonstrate multiphoton interference using a resource-efficient frequency multiplexing scheme, suitable for quantum information applications that demand multiple indistinguishable and pure single photons. In our source, frequency-correlated photon pairs are generated over a wide range of frequencies by pulsed parametric down conversion. Indistinguishable single photons of a predetermined freque… ▽ More We demonstrate multiphoton interference using a resource-efficient frequency multiplexing scheme, suitable for quantum information applications that demand multiple indistinguishable and pure single photons. In our source, frequency-correlated photon pairs are generated over a wide range of frequencies by pulsed parametric down conversion. Indistinguishable single photons of a predetermined frequency are prepared using frequency-resolved detection of one photon to control an electro-optic frequency shift applied to its partner. Measured photon statistics show multiplexing increases the probability of delivering a single photon, without a corresponding increase to multiphoton events. Interference of consecutive outputs is used to bound the single-photon purity and demonstrate the non-classical nature of the emitted light. △ Less

Submitted 24 July, 2019; originally announced July 2019.

Journal ref: Phys. Rev. Applied 14, 014052 (2020)

Deep segmentation networks predict survival of non-small cell lung cancer

Authors: Stephen Baek, Yusen He, Bryan G. Allen, John M. Buatti, Brian J. Smith, Ling Tong, Zhiyu Sun, Jia Wu, Maximilian Diehn, Billy W. Loo, Kristin A. Plichta, Steven N. Seyedin, Maggie Gannon, Katherine R. Cabel, Yusung Kim, Xiaodong Wu

Abstract: Non-small-cell lung cancer (NSCLC) represents approximately 80-85% of lung cancer diagnoses and is the leading cause of cancer-related death worldwide. Recent studies indicate that image-based radiomics features from positron emission tomography-computed tomography (PET/CT) images have predictive power on NSCLC outcomes. To this end, easily calculated functional features such as the maximum and th… ▽ More Non-small-cell lung cancer (NSCLC) represents approximately 80-85% of lung cancer diagnoses and is the leading cause of cancer-related death worldwide. Recent studies indicate that image-based radiomics features from positron emission tomography-computed tomography (PET/CT) images have predictive power on NSCLC outcomes. To this end, easily calculated functional features such as the maximum and the mean of standard uptake value (SUV) and total lesion glycolysis (TLG) are most commonly used for NSCLC prognostication, but their prognostic value remains controversial. Meanwhile, convolutional neural networks (CNN) are rapidly emerging as a new premise for cancer image analysis, with significantly enhanced predictive power compared to other hand-crafted radiomics features. Here we show that CNN trained to perform the tumor segmentation task, with no other information than physician contours, identify a rich set of survival-related image features with remarkable prognostic value. In a retrospective study on 96 NSCLC patients before stereotactic-body radiotherapy (SBRT), we found that the CNN segmentation algorithm (U-Net) trained for tumor segmentation in PET/CT images, contained features having strong correlation with 2- and 5-year overall and disease-specific survivals. The U-net algorithm has not seen any other clinical information (e.g. survival, age, smoking history) than the images and the corresponding tumor contours provided by physicians. Furthermore, through visualization of the U-Net, we also found convincing evidence that the regions of progression appear to match with the regions where the U-Net features identified patterns that predicted higher likelihood of death. We anticipate our findings will be a starting point for more sophisticated non-intrusive patient specific cancer prognosis determination. △ Less

Submitted 8 November, 2019; v1 submitted 26 March, 2019; originally announced March 2019.

A multiple attribute model resolves a conflict between additive and multiplicative models of incentive salience

Authors: Benjamin J. Smith, Stephen J. Read

Abstract: A model of incentive salience as a function of stimulus value and interoceptive state has been previously proposed. In that model, the function differs depending on whether the stimulus is appetitive or aversive; it is multiplicative for appetitive stimuli and additive for aversive stimuli. The authors argued it was necessary to capture data on how extreme changes in salt appetite could move evalu… ▽ More A model of incentive salience as a function of stimulus value and interoceptive state has been previously proposed. In that model, the function differs depending on whether the stimulus is appetitive or aversive; it is multiplicative for appetitive stimuli and additive for aversive stimuli. The authors argued it was necessary to capture data on how extreme changes in salt appetite could move evaluation of an extreme salt solution from negative to positive. We demonstrate that arbitrarily varying this function is unnecessary, and that a multiplicative function is sufficient if one assumes the incentive salience function for an incentive (such as salt) is comprised of multiple stimulus features and multiple interoceptive signals. We show that it is also unnecessary considering the dual-structure approach-aversive nature of the reward system, which results in separate weighting of appetitive and aversive stimulus features. △ Less

Submitted 19 December, 2018; originally announced December 2018.

Experimental test of contextuality in quantum and classical systems

Authors: Aonan Zhang, Huichao Xu, Jie Xie, Han Zhang, Brian J. Smith, M. S. Kim, Lijian Zhang

Abstract: Contextuality is considered as an intrinsic signature of non-classicality, and a crucial resource for achieving unique advantages of quantum information processing. However, recently there have been debates on whether classical fields may also demonstrate contextuality. Here we experimentally configure a contextuality test for optical fields, adopting various definitions of measurement events, and… ▽ More Contextuality is considered as an intrinsic signature of non-classicality, and a crucial resource for achieving unique advantages of quantum information processing. However, recently there have been debates on whether classical fields may also demonstrate contextuality. Here we experimentally configure a contextuality test for optical fields, adopting various definitions of measurement events, and analyse how the definitions affect the emergence of non-classical correlations. The heralded single photon state, a typical non-classical light field, manifests contextuality in our setup, while contextuality for classical coherent fields strongly depends on the specific definition of measurement events which is equivalent to filtering the non-classical component of the input state. Our results highlight the importance of definition of measurement events to demonstrate contextuality, and link the contextual correlations to non-classicality defined by quasi-probabilities in phase space. △ Less

Submitted 26 February, 2019; v1 submitted 18 October, 2018; originally announced October 2018.

Comments: 17 pages, 7 figures

Journal ref: Phys. Rev. Lett. 122, 080401 (2019)

Measuring the quantum state of a photon pair entangled in frequency and time

Authors: Alex O. C. Davis, Valerian Thiel, Brian J. Smith

Abstract: We present a technique to completely characterise the spectral-temporal wave function of a broadband photon pair using spectral-shearing interferometry. Our method is fully self-referencing and is generalisable across a wide range of wavelengths. To demonstrate, we generate an entangled photon pair with controllable time-frequency entanglement and perform a full reconstruction. These results allow… ▽ More We present a technique to completely characterise the spectral-temporal wave function of a broadband photon pair using spectral-shearing interferometry. Our method is fully self-referencing and is generalisable across a wide range of wavelengths. To demonstrate, we generate an entangled photon pair with controllable time-frequency entanglement and perform a full reconstruction. These results allow previously unobservable features of quantum states to be measured and utilised for the first time. We foresee this will unlock new opportunities in high-dimensional quantum technology, enabling the development of novel ways of generating and interacting with quantum systems. △ Less

Submitted 11 September, 2018; originally announced September 2018.

Experimental single-photon pulse characterization by electro-optic shearing interferometry

Authors: Alex O. C Davis, Valérian Thiel, Michał Karpiński, Brian J. Smith

Abstract: The ability to characterize the complete quantum state of light is essential for both fundamental and applied science. For single photons the quantum state is provided by the mode that it occupies. The spectral temporal mode structure of light has recently emerged as an essential means for quantum information science. Here we experimentally demonstrate a self-referencing technique to completely de… ▽ More The ability to characterize the complete quantum state of light is essential for both fundamental and applied science. For single photons the quantum state is provided by the mode that it occupies. The spectral temporal mode structure of light has recently emerged as an essential means for quantum information science. Here we experimentally demonstrate a self-referencing technique to completely determine the pulse-mode structure of single photons by means of spectral shearing interferometry. We detail the calibration and resolution of the measurement and discuss challenges and critical requirements for future advances of this method. △ Less

Submitted 20 February, 2018; originally announced February 2018.

Journal ref: Phys. Rev. A 98, 023840 (2018)

Entanglement Swapping for Generation of Heralded Time-Frequency-Entangled Photon Pairs

Authors: Dashiell L. P. Vitullo, M. G. Raymer, B. J. Smith, Michał Karpiński, L. Mejling, K. Rottwitt

Abstract: Photonic time-frequency entanglement is a promising resource for quantum information processing technologies. We investigate swapping of continuous-variable entanglement in the time-frequency degree of freedom using three-wave mixing in the low-gain regime with the aim of producing heralded biphoton states with high purity and low multi-pair probability. Heralding is achieved by combining one phot… ▽ More Photonic time-frequency entanglement is a promising resource for quantum information processing technologies. We investigate swapping of continuous-variable entanglement in the time-frequency degree of freedom using three-wave mixing in the low-gain regime with the aim of producing heralded biphoton states with high purity and low multi-pair probability. Heralding is achieved by combining one photon from each of two biphoton sources via sum-frequency generation to create a herald photon. We present a realistic model with pulsed pumps, investigate the effects of resolving the frequency of the herald photon, and find that frequency-resolving measurement of the herald photon is necessary to produce high-purity biphotons. We also find a trade-off between the rate of successful entanglement swapping and both the purity and quantified entanglement resource (negativity) of the heralded biphoton state. △ Less

Submitted 21 August, 2018; v1 submitted 31 January, 2018; originally announced February 2018.

Comments: 17 pages and 9 figures. Version 3 corrects an error in the count rate theory and calculations, fixes a few grammatical and typographical errors, improves formatting, and adds the journal reference

Journal ref: Phys. Rev. A 98, 023836 (2018)

Stellar Population Synthesis of star forming clumps in galaxy pairs and non-interacting spiral galaxies

Authors: Javier Zaragoza-Cardiel, Beverly J. Smith, Margarita Rosado, John E. Beckman, Theodoros Bitsakis, Artemi Camps-Fariña, Joan Font, Isaiah S. Cox

Abstract: We have identified 1027 star forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in $8\rm{μm}$ observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy… ▽ More We have identified 1027 star forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in $8\rm{μm}$ observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution (SED) of our clumps with the Code Investigating GALaxy Emission (CIGALE) using a double exponentially declined star formation history (SFH). We derive SFRs, stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an AGN for these clumps. The resolved star formation main sequence holds on 2.5kpc scales, although it does not hold on 1kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that SFR is enhanced through the disk and in the tidal features relative to normal spirals. △ Less

Submitted 6 February, 2018; v1 submitted 14 December, 2017; originally announced December 2017.

Comments: Accepted for publication in ApJS. 20 pages, 10 figures, 6 tables

Journal ref: ApJS, 2018, Volume 234, 35

Diffuse X-ray-emitting Gas in Major Mergers

Authors: Beverly J. Smith, Kristen Campbell, Curtis Struck, Roberto Soria, Douglas Swartz, Macon Magno, Brianne Dunn, Mark L. Giroux

Abstract: Using archived data from the Chandra X-ray telescope, we have extracted the diffuse X-ray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L(X)(gas)) with the global star formation rate (SFR).… ▽ More Using archived data from the Chandra X-ray telescope, we have extracted the diffuse X-ray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L(X)(gas)) with the global star formation rate (SFR). After correction for absorption within the target galaxy, we do not see strong trend of L(X)(gas)/SFR with SFR or merger stage for galaxies with SFR > 1 M(sun) yr^-1. For these galaxies, the median L(X)(gas)/SFR is 5.5 X 10^39 ((erg s^-1)/M(sun) yr^-1)), similar to that of normal spiral galaxies. These results suggest that stellar feedback in star forming galaxies reaches an approximately steady state condition, in which a relatively constant fraction of about 2% of the total energy output from supernovae and stellar winds is converted into X-ray flux. Three late-stage merger remnants with low SFRs and high K band luminosities (L(K)) have enhanced L(X)(gas)/SFR; their UV/IR/optical colors suggest that they are post-starburst galaxies, perhaps in the process of becoming ellipticals. Systems with L(K) < 10^10 L(sun) have lower L(X)(gas)/SFR ratios than the other galaxies in our sample, perhaps due to lower gravitational fields or lower metallicities. We see no relation between L(X)(gas)/SFR and Seyfert activity in this sample, suggesting that feedback from active galactic nuclei is not a major contributor to the hot gas in our sample galaxies. △ Less

Submitted 11 December, 2017; originally announced December 2017.

Comments: Astronomical Journal, in press; 43 pages, 24 figures

Measuring the single-photon temporal-spectral wave function

Authors: Alex O. C. Davis, Valérian Thiel, Michał Karpiński, Brian J. Smith

Abstract: Temporal-spectral modes of light provide a fundamental window into the nature of atomic and molecular systems and offer robust means for information encoding. Methods to precisely characterize the temporal-spectral state of light at the single-photon level thus play a central role in understanding quantum emitters and are a key requirement for quantum technologies that harness single-photon states… ▽ More Temporal-spectral modes of light provide a fundamental window into the nature of atomic and molecular systems and offer robust means for information encoding. Methods to precisely characterize the temporal-spectral state of light at the single-photon level thus play a central role in understanding quantum emitters and are a key requirement for quantum technologies that harness single-photon states. Here we demonstrate an optical reference-free method, which melds techniques from ultrafast metrology and single-photon spectral detection, to characterize the temporal-spectral state of single photons. This provides a robust, wavelength-tunable approach for rapid characterization of pulsed single-photon states that underpins emerging optical quantum technologies based upon the temporal-spectral mode structure of quantum light. △ Less

Submitted 20 February, 2018; v1 submitted 15 September, 2017; originally announced September 2017.

Journal ref: Phys. Rev. Lett. 121, 083602 (2018)

Convergence diagnostics for MCMC draws of a categorical variable

Authors: Benjamin E. Deonovic, Brian J. Smith

Abstract: Markov Chain Monte Carlo (MCMC) is a popular class of statistical methods for simulating autocorrelated draws from target distributions, including posterior distributions in Bayesian analysis. An important consideration in using simulated MCMC draws for inference is that the sampling algorithm has converged to the distribution of interest. Since the distribution is typically of a non-standard form… ▽ More Markov Chain Monte Carlo (MCMC) is a popular class of statistical methods for simulating autocorrelated draws from target distributions, including posterior distributions in Bayesian analysis. An important consideration in using simulated MCMC draws for inference is that the sampling algorithm has converged to the distribution of interest. Since the distribution is typically of a non-standard form, convergence cannot generally be proven and, instead, is assessed with convergence diagnostics. Although parameters used in the MCMC framework are typically continuous, there are many situations in which simulating a categorical variable is desired. Examples include indicators for model inclusion in Bayesian variable selection and latent categorical component variables in mixture modeling. Traditional convergence diagnostics are designed for continuous variables and may be inappropriate for categorical variables. In this paper two convergence diagnostic methods are considered which are appropriate for MCMC data. The diagnostics discussed in the paper utilize chi-squared test statistics for dependent data. Performance of the convergence diagnostics is evaluated under various simulations. Finally, the diagnostics are applied to a real data set where reversible jump MCMC is used to sample from a finite mixture model. △ Less

Submitted 15 June, 2017; originally announced June 2017.

Comments: 36 pages, 8 figures

Pulsed single-photon spectrometer by frequency-to-time mapping using chirped fiber Bragg gratings

Authors: Alex O. C. Davis, Paul M. Saulnier, Michal Karpinski, Brian J. Smith

Abstract: A fiber-integrated spectrometer for single-photon pulses outside the telecommunications wavelength range based upon frequency-to-time mapping, implemented by chromatic group delay dispersion (GDD), and precise temporally-resolved single-photon counting, is presented. A chirped fiber Bragg grating provides low-loss GDD, mapping the frequency distribution of an input pulse onto the temporal envelope… ▽ More A fiber-integrated spectrometer for single-photon pulses outside the telecommunications wavelength range based upon frequency-to-time mapping, implemented by chromatic group delay dispersion (GDD), and precise temporally-resolved single-photon counting, is presented. A chirped fiber Bragg grating provides low-loss GDD, mapping the frequency distribution of an input pulse onto the temporal envelope of the output pulse. Time-resolved detection with fast single-photon-counting modules enables monitoring of a wavelength range from 825 nm to 835 nm with nearly uniform efficiency at 55 pm resolution (24 GHz at 830 nm). To demonstrate the versatility of this technique, spectral interference of heralded single photons and the joint spectral intensity distribution of a photon-pair source are measured. This approach to single-photon-level spectral measurements provides a route to realize applications of time-frequency quantum optics at visible and near-infrared wavelengths, where multiple spectral channels must be simultaneously monitored. △ Less

Submitted 29 July, 2017; v1 submitted 10 October, 2016; originally announced October 2016.

Comments: 8 pages, 3 figures, published version

Journal ref: Opt. Express 25, 12804 (2017)

Spectral shearing of quantum light pulses by electro-optic phase modulation

Authors: Laura J. Wright, Michal Karpinski, Christoph Soeller, Brian J. Smith

Abstract: Frequency conversion of non-classical light enables robust encoding of quantum information based upon spectral multiplexing that is particularly well-suited to integrated-optics platforms. Here we present an intrinsically deterministic linear-optics approach to spectral shearing of quantum light pulses and show it preserves the wave-packet coherence and quantum nature of light. The technique is ba… ▽ More Frequency conversion of non-classical light enables robust encoding of quantum information based upon spectral multiplexing that is particularly well-suited to integrated-optics platforms. Here we present an intrinsically deterministic linear-optics approach to spectral shearing of quantum light pulses and show it preserves the wave-packet coherence and quantum nature of light. The technique is based upon an electro-optic Doppler shift to implement frequency shear of heralded single-photon wave packets by $\pm 200$ GHz, which can be scaled to an arbitrary shift. These results demonstrate a reconfigurable, unitary method to controlling the spectral-temporal mode structure of quantum light. △ Less

Submitted 10 January, 2017; v1 submitted 2 May, 2016; originally announced May 2016.

Comments: Final version. 5 pages, 3 figures

Journal ref: Phys. Rev. Lett. 118, 023601 (2017)

Bandwidth manipulation of quantum light by an electro-optic time lens

Authors: Michal Karpinski, Michal Jachura, Laura J. Wright, Brian J. Smith

Abstract: The ability to manipulate the spectral-temporal waveform of optical pulses has enabled a wide range of applications from ultrafast spectroscopy to high-speed communications. Extending these concepts to quantum light has the potential to enable breakthroughs in optical quantum science and technology. However, filtering and amplifying often employed in classical pulse shaping techniques are incompat… ▽ More The ability to manipulate the spectral-temporal waveform of optical pulses has enabled a wide range of applications from ultrafast spectroscopy to high-speed communications. Extending these concepts to quantum light has the potential to enable breakthroughs in optical quantum science and technology. However, filtering and amplifying often employed in classical pulse shaping techniques are incompatible with non-classical light. Controlling the pulsed mode structure of quantum light requires efficient means to achieve deterministic, unitary manipulation that preserves fragile quantum coherences. Here we demonstrate an electro-optic method for modifying the spectrum of non-classical light by employing a time lens. In particular we show highly-efficient wavelength-preserving six-fold compression of single-photon spectral intensity bandwidth, enabling over a two-fold increase of single-photon flux into a spectrally narrowband absorber. These results pave the way towards spectral-temporal photonic quantum information processing and facilitate interfacing of different physical platforms where quantum information can be stored or manipulated. △ Less

Submitted 29 July, 2017; v1 submitted 8 April, 2016; originally announced April 2016.

Comments: Final version. 7 pages, 4 figures + supplementary: 6 pages, 2 figures. MK & MJ -- equal contribution

Journal ref: Nature Photonics 11, 53-57 (2017)

A chip-based array of near-identical, pure, heralded single photon sources

Authors: Justin B. Spring, Paolo L. Mennea, Benjamin J. Metcalf, Peter C. Humphreys, James C. Gates, Helen L. Rogers, Christoph Soeller, Brian J. Smith, W. Steven Kolthammer, Peter G. R. Smith, Ian A. Walmsley

Abstract: Interference between independent single photons is perhaps the most fundamental interaction in quantum optics. It has become increasingly important as a tool for optical quantum information science, as one of the rudimentary quantum operations, together with photon detection, for generating entanglement between non-interacting particles. Despite this, demonstrations of large-scale photonic network… ▽ More Interference between independent single photons is perhaps the most fundamental interaction in quantum optics. It has become increasingly important as a tool for optical quantum information science, as one of the rudimentary quantum operations, together with photon detection, for generating entanglement between non-interacting particles. Despite this, demonstrations of large-scale photonic networks involving more than two independent sources of quantum light have been limited due to the difficulty in constructing large arrays of high-quality single photon sources. Here, we solve the key challenge, reporting a novel array of more than eighteen near-identical, low-loss, high-purity, heralded single photon sources achieved using spontaneous four-wave mixing (SFWM) on a silica chip. We verify source quality through a series of heralded Hong-Ou-Mandel experiments, and further report the experimental three-photon extension of the entire Hong-Ou-Mandel interference curves, which map out the interference landscape between three independent single photon sources for the first time. △ Less

Submitted 22 March, 2016; originally announced March 2016.

Comments: 16 pages including supplementary information

Journal ref: Optica 4, 90-96 (2017)

A Comparative Study of Knots of Star Formation in Interacting vs. Spiral Galaxies

Authors: Beverly J. Smith, Javier Zaragoza-Cardiel, Curtis Struck, Susan Olmsted, Keith Jones

Abstract: Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published H-alpha images, we have compared the star formation rates of ~700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting ga… ▽ More Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published H-alpha images, we have compared the star formation rates of ~700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high star formation rates than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The star formation rates of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest star formation rates, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to H-alpha, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in H-alpha. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus the star forming regions in interacting galaxies are more luminous, dustier, or younger on average. △ Less

Submitted 8 February, 2016; v1 submitted 11 January, 2016; originally announced January 2016.

Comments: Astronomical Journal, in press

Two-photon quantum walk in a multimode fiber

Authors: Hugo Defienne, Marco Barbieri, Ian A. Walmsley, Brian J. Smith, Sylvain Gigan

Abstract: Multi-photon propagation in connected structures - a quantum walk - offers the potential for simulating complex physical systems and provides a route to universal quantum computation. Increasing the complexity of quantum photonic networks where the walk occurs is essential for many applications. Here, we implement a quantum walk of indistinguishable photon pairs in a multimode fiber supporting 380… ▽ More Multi-photon propagation in connected structures - a quantum walk - offers the potential for simulating complex physical systems and provides a route to universal quantum computation. Increasing the complexity of quantum photonic networks where the walk occurs is essential for many applications. Here, we implement a quantum walk of indistinguishable photon pairs in a multimode fiber supporting 380 modes. Using wavefront shaping, we control the propagation of the two-photon state through the fiber in which all modes are coupled. Excitation of arbitrary output modes of the system is realized by controlling classical and quantum interferences. This experiment demonstrates a highly multimode platform for multi-photon interference experiments and provides a powerful method to program a general high-dimensional multiport optical circuit. This work paves the way for the next generation of photonic devices for quantum simulation, computing and communication. △ Less

Submitted 17 March, 2016; v1 submitted 13 April, 2015; originally announced April 2015.

Comments: 11 pages, 4 figures

Journal ref: Science Advances 29 Jan 2016: Vol. 2, no. 1, e1501054