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Soft X-ray Reflection Ptychography
Authors:
Damian Guenzing,
Dayne Y. Sasaki,
Alexander S. Ditter,
Abraham L. Levitan,
Eric M. Gullikson,
Scott Dhuey,
Arian Gashi,
Hendrik Ohldag,
Sujoy Roy,
David A. Shapiro,
Riccardo Comin,
Sophie A. Morley
Abstract:
Scanning transmission X-ray microscopy and ptychography have become mature tools for high-resolution, element-specific imaging of nanoscale structures. However, transmission geometries impose stringent constraints on sample thickness and preparation, thereby limiting investigations of extended or bulk specimens, especially in the soft X-ray region. Here, we demonstrate reflection geometry soft X-r…
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Scanning transmission X-ray microscopy and ptychography have become mature tools for high-resolution, element-specific imaging of nanoscale structures. However, transmission geometries impose stringent constraints on sample thickness and preparation, thereby limiting investigations of extended or bulk specimens, especially in the soft X-ray region. Here, we demonstrate reflection geometry soft X-ray ptychography as a robust imaging mode. Instrumental feasibility and spatial resolution are established using a lithographically defined Siemens star and barcode test pattern on a multilayer substrate. We empirically demonstrate a full-pitch spatial resolution of ca. 45 nm from Fourier ring correlation analysis of the reconstructed object. The results highlight the potential of the reflection geometry for nondestructive X-ray studies of materials without the need for transmissive samples.
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Submitted 28 January, 2026;
originally announced January 2026.
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Entanglement of a nuclear spin qubit register in silicon photonics
Authors:
Hanbin Song,
Xueyue Zhang,
Lukasz Komza,
Niccolo Fiaschi,
Yihuang Xiong,
Yiyang Zhi,
Scott Dhuey,
Adam Schwartzberg,
Thomas Schenkel,
Geoffroy Hautier,
Zi-Huai Zhang,
Alp Sipahigil
Abstract:
Color centers provide an optical interface to quantum registers based on electron and nuclear spin qubits in solids. The T center in silicon is an emerging spin-photon interface that combines telecom O-band optical transitions and an electron spin in a scalable photonics platform. In this work, we demonstrate the initialization, coherent control, and state readout of a three-qubit register based o…
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Color centers provide an optical interface to quantum registers based on electron and nuclear spin qubits in solids. The T center in silicon is an emerging spin-photon interface that combines telecom O-band optical transitions and an electron spin in a scalable photonics platform. In this work, we demonstrate the initialization, coherent control, and state readout of a three-qubit register based on the electron spin of a T center coupled to a hydrogen and a silicon nuclear spin. The spin register exhibits spin echo coherence times of $0.41(2)$~ms for the electron spin, $112(12)$~ms for the hydrogen nuclear spin, and $67(7)$~ms for the silicon nuclear spin. We use nuclear-nuclear two-qubit gates to generate entanglement between the two nuclear spins with a fidelity of $F=0.77(3)$ and a coherence time of $T^*_2=2.60(8)$~ms. Our results show that a T center in silicon photonics can realize a multi-qubit register with an optical interface for quantum communication.
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Submitted 11 December, 2025; v1 submitted 21 April, 2025;
originally announced April 2025.
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The dipolar Aleppo lattice: Ground state ordering and ergodic dynamics in the absence of vertex frustration
Authors:
Gopi Mahato,
Davis Crater,
Christian Hoyt,
Duncan Miertschin,
Balaram Regmi,
Kevin Hofhuis,
Scott Dhuey,
Barat Achinuq,
Francesco Caravelli,
Alan Farhan
Abstract:
We introduce the Aleppo spin ice geometry, another variation of decimated square ice patterns, which in contrast to similar systems previously studied, does not exhibit vertex frustration. Using synchrotron-based photoemission electron microscopy, we directly visualize low-energy states achieved after thermal annealing, in addition to temperature-dependent moment fluctuations. The results reveal t…
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We introduce the Aleppo spin ice geometry, another variation of decimated square ice patterns, which in contrast to similar systems previously studied, does not exhibit vertex frustration. Using synchrotron-based photoemission electron microscopy, we directly visualize low-energy states achieved after thermal annealing, in addition to temperature-dependent moment fluctuations. The results reveal the observation of ground state patterns and the absence of ergodicity-breaking dynamics. Our observations further confirm vertex frustration to be an important criterion for the emergence of ergodicity transitions.
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Submitted 8 January, 2025; v1 submitted 6 January, 2025;
originally announced January 2025.
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Room-temperature valley-selective emission in Si-MoSe2 heterostructures enabled by high-quality-factor chiroptical cavities
Authors:
Feng Pan,
Xin Li,
Amalya C. Johnson,
Scott Dhuey,
Ashley Saunders,
Meng-Xia Hu,
Jefferson P. Dixon,
Sahil Dagli,
Sze-Cheung Lau,
Tingting Weng,
Chih-Yi Chen,
Jun-Hao Zeng,
Rajas Apte,
Tony F. Heinz,
Fang Liu,
Zi-Lan Deng,
Jennifer A. Dionne
Abstract:
Transition metal dichalcogenides possess valley pseudospin, enabling coupling between photon spin and electron spin for classical and quantum information processing. However, rapid valley-dephasing processes have impeded the development of scalable, high-performance valleytronic devices operating at room temperature. Here we demonstrate that a chiral resonant metasurface can enable room-temperatur…
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Transition metal dichalcogenides possess valley pseudospin, enabling coupling between photon spin and electron spin for classical and quantum information processing. However, rapid valley-dephasing processes have impeded the development of scalable, high-performance valleytronic devices operating at room temperature. Here we demonstrate that a chiral resonant metasurface can enable room-temperature valley-selective emission in MoSe2 monolayers independent of excitation polarization. This platform provides circular eigen-polarization states with a high quality factor (Q-factor) and strong chiral near-field enhancement. The fabricated Si chiral metasurfaces exhibit chiroptical resonances with Q-factors up to 450 at visible wavelengths. We reveal degrees of circular polarization (DOP) reaching a record high of 0.5 at room temperature. Our measurements show that the high DOP can be attributed to the significantly increased chiroptical local density of states, which enhances valley-specific radiative transition rates by a factor of ~13. Our work could facilitate the development of ultracompact chiral classical and quantum light sources.
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Submitted 23 November, 2025; v1 submitted 15 September, 2024;
originally announced September 2024.
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Probing Plexciton Emission from 2D Materials on Gold Nanotrenches
Authors:
Junze Zhou,
P. A. D. Gonçalves,
Fabrizio Riminucci,
Scott Dhuey,
Edward Barnard,
Adam Schwartzberg,
F. Javier García de Abajo,
Alexander Weber-Bargioni
Abstract:
Probing strongly coupled quasiparticle excitations at their intrinsic length scales offers unique insights into their properties and facilitates the design of devices with novel functionalities. In this work, we investigate the formation and emission characteristics of plexcitons, arising from the interaction between surface plasmons in narrow gold nanotrenches and excitons in monolayer WSe2. We s…
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Probing strongly coupled quasiparticle excitations at their intrinsic length scales offers unique insights into their properties and facilitates the design of devices with novel functionalities. In this work, we investigate the formation and emission characteristics of plexcitons, arising from the interaction between surface plasmons in narrow gold nanotrenches and excitons in monolayer WSe2. We study this strong plasmon-exciton coupling in both the far-field and the near-field. Specifically, we observe a Rabi splitting in the far-field reflection spectra of about 80 meV under ambient conditions, consistent with our theoretical modeling. Using a custom-designed near-field probe, we find that plexciton emission originates predominantly from the lower-frequency branch, which we can directly probe and map the local field distribution. We precisely determine the plexciton extension, similar to the trench width, with nanometric precision via collecting spectra at controlled probe locations. Our work opens exciting prospects for nanoscale mapping and engineering of plexcitons in complex nanostructures with potential applications in nanophotonic devices, optoelectronics, and quantum electrodynamics in nanoscale cavities.
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Submitted 7 April, 2024;
originally announced April 2024.
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Triangular Cross-Section Beam Splitters in Silicon Carbide for Quantum Information Processing
Authors:
Sridhar Majety,
Pranta Saha,
Zbynka Kekula,
Scott Dhuey,
Marina Radulaski
Abstract:
Triangular cross-section color center photonics in silicon carbide is a leading candidate for scalable implementation of quantum hardware. Within this geometry, we model low-loss beam splitters for applications in key quantum optical operations such as entanglement and single-photon interferometry. We consider triangular cross-section single-mode waveguides for the design of a directional coupler.…
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Triangular cross-section color center photonics in silicon carbide is a leading candidate for scalable implementation of quantum hardware. Within this geometry, we model low-loss beam splitters for applications in key quantum optical operations such as entanglement and single-photon interferometry. We consider triangular cross-section single-mode waveguides for the design of a directional coupler. We optimize parameters for a 50:50 beam splitter. Finally, we test the experimental feasibility of the designs by fabricating triangular waveguides in an ion beam etching process and identify suitable designs for short-term implementation.
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Submitted 13 April, 2024; v1 submitted 13 November, 2023;
originally announced November 2023.
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Quantifying the Topology of Magnetic Skyrmions in three Dimensions
Authors:
David Raftrey,
Simone Finizio,
Rajesh V. Chopdekar,
Scott Dhuey,
Temuujin Bayaraa,
Paul Ashby,
Jörg Raabe,
Tiffany Santos,
Sinéad Griffin,
Peter Fischer
Abstract:
Magnetic skyrmions have so far been treated as two-dimensional spin structures characterized by a topological winding number describing the rotation of spins across the skyrmion. However, in real systems with a finite thickness of the material being larger than the magnetic exchange length, the skyrmion spin texture extends into the third dimension and cannot be assumed as homogeneous. Using soft…
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Magnetic skyrmions have so far been treated as two-dimensional spin structures characterized by a topological winding number describing the rotation of spins across the skyrmion. However, in real systems with a finite thickness of the material being larger than the magnetic exchange length, the skyrmion spin texture extends into the third dimension and cannot be assumed as homogeneous. Using soft x-ray laminography we reconstruct with about 20nm spatial (voxel) resolution the full three-dimensional spin texture of a skyrmion in an 800 nm diameter and 95 nm thin disk patterned into a trilayer [Ir/Co/Pt] thin film structure. A quantitative analysis finds that the evolution of the radial profile of the topological skyrmion number and the chirality is non-uniform across the thickness of the disk. Estimates of local micromagnetic energy densities suggest that the changes in topological profile are related to non-uniform competing energetic interactions. Theoretical calculations and micromagnetic simulations are consistent with the experimental findings. Our results provide the foundation for nanoscale magnetic metrology for future tailored spintronics devices using topology as a design parameter, and have the potential to reverse-engineer a spin Hamiltonian from macroscopic data, tying theory more closely to experiment.
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Submitted 26 June, 2023;
originally announced June 2023.
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Bose-Einstein Condensation in Gap-Confined Exciton-Polariton States
Authors:
F. Riminucci,
A. Gianfrate,
D. Nigro,
V. Ardizzone,
S. Dhuey,
L. Francaviglia,
K. Baldwin,
L. N. Pfeiffer,
D. Trypogeorgos,
A. Schwartzberg,
D. Gerace,
D. Sanvitto
Abstract:
The development of patterned multi-quantum well heterostructures in GaAs/AlGaAs waveguides has recently allowed to achieve exciton-polariton condensation in a topologically protected bound state in the continuum (BIC). Remarkably, condensation occurred above a saddle point of the polariton dispersion. A rigorous analysis of the condensation phenomenon in these systems, as well as the role of the B…
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The development of patterned multi-quantum well heterostructures in GaAs/AlGaAs waveguides has recently allowed to achieve exciton-polariton condensation in a topologically protected bound state in the continuum (BIC). Remarkably, condensation occurred above a saddle point of the polariton dispersion. A rigorous analysis of the condensation phenomenon in these systems, as well as the role of the BIC, is still missing. In the present Letter we theoretically and experimentally fill this gap, by showing that polariton confinement resulting from the negative effective mass and the photonic energy gap in the dispersion play a key role in enhancing the relaxation towards the condensed state. In fact, our results show that low-threshold polariton condensation is achieved within the effective trap created by the exciting laser spot regardless of whether the resulting confined mode is long-lived (polariton BIC) or short-lived (lossy mode). In both cases, the spatial quantization of the polariton condensate and the threshold differences associated to the corresponding state lifetime are measured and characterized. For a given negative mass, a slightly lower condensation threshold from the polariton BIC mode is found and associated to its suppressed radiative losses as compared to the lossy one.
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Submitted 5 June, 2023;
originally announced June 2023.
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Fabrication of Nanostructured GaAs/AlGaAs Waveguide for Low-Density Polariton Condensation from a Bound State in the Continuum
Authors:
F. Riminucci,
V. Ardizzone,
L. Francaviglia,
M. Lorenzon,
C. Stavrakas,
S. Dhuey,
A. Schwartzberg,
S. Zanotti,
D. Gerace,
K. Baldwin,
L. N. Pfeiffer,
G. Gigli,
D. F. Ogletree,
A. Weber-Bargioni,
S. Cabrini,
D. Sanvitto
Abstract:
Exciton-polaritons are hybrid light-matter states that arise from strong coupling between an exciton resonance and a photonic cavity mode. As bosonic excitations, they can undergo a phase transition to a condensed state that can emit coherent light without a population inversion. This aspect makes them good candidates for thresholdless lasers, yet short exciton-polariton lifetime has made it diffi…
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Exciton-polaritons are hybrid light-matter states that arise from strong coupling between an exciton resonance and a photonic cavity mode. As bosonic excitations, they can undergo a phase transition to a condensed state that can emit coherent light without a population inversion. This aspect makes them good candidates for thresholdless lasers, yet short exciton-polariton lifetime has made it difficult to achieve condensation at very low power densities. In this sense, long-lived symmetry-protected states are excellent candidates to overcome the limitations that arise from the finite mirror reflectivity of monolithic microcavities. In this work we use a photonic symmetry protected bound state in the continuum coupled to an excitonic resonance to achieve state-of-the-art polariton condensation threshold in GaAs/AlGaAs waveguide. Most important, we show the influence of fabrication control and how surface passivation via atomic layer deposition provides a way to reduce exciton quenching at the grating sidewalls.
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Submitted 11 May, 2022;
originally announced May 2022.
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Direct observation of a dynamical glass transition in a nanomagnetic artificial Hopfield network
Authors:
Michael Saccone,
Francesco Caravelli,
Kevin Hofhuis,
Sergii Parchenko,
Yorick A. Birkhölzer,
Scott Dhuey,
Armin Kleibert,
Sebastiaan van Dijken,
Cristiano Nisoli,
Alan Farhan
Abstract:
Spin glasses, generally defined as disordered systems with randomized competing interactions, are a widely investigated complex system. Theoretical models describing spin glasses are broadly used in other complex systems, such as those describing brain function, error-correcting codes, or stock-market dynamics. This wide interest in spin glasses provides strong motivation to generate an artificial…
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Spin glasses, generally defined as disordered systems with randomized competing interactions, are a widely investigated complex system. Theoretical models describing spin glasses are broadly used in other complex systems, such as those describing brain function, error-correcting codes, or stock-market dynamics. This wide interest in spin glasses provides strong motivation to generate an artificial spin glass within the framework of artificial spin ice systems. Here, we present the experimental realization of an artificial spin glass consisting of dipolar coupled single-domain Ising-type nanomagnets arranged onto an interaction network that replicates the aspects of a Hopfield neural network. Using cryogenic x-ray photoemission electron microscopy (XPEEM), we performed temperature-dependent imaging of thermally driven moment fluctuations within these networks and observed characteristic features of a two-dimensional Ising spin glass. Specifically, the temperature dependence of the spin glass correlation function follows a power law trend predicted from theoretical models on two-dimensional spin glasses. Furthermore, we observe clear signatures of the hard to observe rugged spin glass free energy in the form of sub-aging, out of equilibrium autocorrelations and a transition from stable to unstable dynamics.
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Submitted 4 February, 2022;
originally announced February 2022.
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Creation and confirmation of Hopfions in magnetic multilayer systems
Authors:
N. Kent,
N. Reynolds,
D. Raftrey,
I. T. G. Campbell,
S. Virasawmy,
S. Dhuey,
R. V. Chopdekar,
A. Hierro-Rodriguez,
A. Sorrentino,
E. Pereiro,
S. Ferrer,
F. Hellman,
P. Sutcliffe,
P. Fischer
Abstract:
Topological solitons have been studied for decades in classical field theories, and have started recently to impact condensed matter physics. Among those solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and magnetic Hopfions are three-dimensional topological solitons that can be formed from a closed loop of a twisted skyrmion st…
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Topological solitons have been studied for decades in classical field theories, and have started recently to impact condensed matter physics. Among those solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and magnetic Hopfions are three-dimensional topological solitons that can be formed from a closed loop of a twisted skyrmion string. Whereas intense research is underway with magnetic skyrmions towards a fundamental understanding and potential applications in advanced storage and logic devices, the experimental creation and confirmation of magnetic Hopfions has been elusive so far. Theoretical models suggest that Hopfions can be stabilized in frustrated or chiral magnetic systems, and that target skymions can be transformed into Hopfions by adapting their perpendicular magnetic anisotropy. Here, we present experimental evidence of magnetic Hopfions that were created in magnetic Ir/Co/Pt multilayers shaped into nanoscale disks, which are known to host target skyrmions. The three-dimensional spin texture, which distinguishes magnetic Hopfions from target skyrmions was confirmed by combining two advanced element-specific magnetic X-ray microscopy techniques with about 20-30nm lateral resolution, using X-ray magnetic circular dichroism effect as magnetic contrast mechanism in surface-sensitive X-ray photoemission electron microscopy and bulk-sensitive soft x-ray transmission microscopy. We anticipate that these results will stimulate further investigations of Hopfions with different topologies and their potential application in three-dimensional spintronics devices.
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Submitted 16 October, 2020;
originally announced October 2020.
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Spontaneous Magnetic Superdomain Wall Fluctuations in an Artificial Antiferromagnet
Authors:
X. M. Chen,
B. Farmer,
J. S. Woods,
S. Dhuey,
W. Hu,
C. Mazzoli,
S. B. Wilkins,
I. K. Robinson,
L. E. De Long,
S. Roy,
J. T. Hastings
Abstract:
Collective dynamics often play an important role in determining the stability of ground states for both naturally occurring materials and metamaterials. We studied the temperature dependent dynamics of antiferromagnetically ordered superdomains in a square artificial spin lattice using soft x-ray photon correlation spectroscopy. We observed an exponential slowing down of superdomain wall motion be…
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Collective dynamics often play an important role in determining the stability of ground states for both naturally occurring materials and metamaterials. We studied the temperature dependent dynamics of antiferromagnetically ordered superdomains in a square artificial spin lattice using soft x-ray photon correlation spectroscopy. We observed an exponential slowing down of superdomain wall motion below the AF onset temperature, similar to the behavior of typical bulk antiferromagnets. Using a continuous time random walk model we show that these superdomain walls undergo low-temperature ballistic and high-temperature diffusive motions.
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Submitted 9 September, 2019; v1 submitted 15 September, 2018;
originally announced September 2018.
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Magnonic band gap and mode hybridization in continuous Permalloy film induced by vertical coupling with an array of Permalloy ellipses
Authors:
Piotr Graczyk,
Maciej Krawczyk,
Scott Dhuey,
Wei-Gang Yang,
Holger Schmidt,
Gianluca Gubbiotti
Abstract:
We investigate magnonic band structure in thin homogeneous permalloy film decorated with periodic array of elliptically shaped permalloy dots and separated by non-magnetic Pt spacer. We demonstrated experimentally formation of the magnonic band structure for Damon-Eshbach wave propagating in permalloy film with the band gap opened at the Brillouin zone border and band splitting at smaller wavenumb…
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We investigate magnonic band structure in thin homogeneous permalloy film decorated with periodic array of elliptically shaped permalloy dots and separated by non-magnetic Pt spacer. We demonstrated experimentally formation of the magnonic band structure for Damon-Eshbach wave propagating in permalloy film with the band gap opened at the Brillouin zone border and band splitting at smaller wavenumbers, due to the Bragg interference and interaction of propagating wave of the continuous film with a standing resonant mode of the nano-ellipses, respectively. The shape anisotropy of the permalloy nanodots allows to control the spin wave dynamics through the switch between two states of the magnetization with respect to the underneath film magnetization, thus enabling magnonic band structure reprogrammability. With numerical analysis we show, that predominant role in formation of the magnonic band structure is played by a vertical dynamic coupling between propagating wave in the film and magnetization oscillations in the nanodots.
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Submitted 29 August, 2018; v1 submitted 30 May, 2018;
originally announced May 2018.
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Experimental verification of Landauer's principle in erasure of nanomagnetic memory bits
Authors:
J. Hong,
B. Lambson,
S. Dhuey,
J. Bokor
Abstract:
In 1961, R. Landauer proposed the principle that logical irreversibility is associated with physical irreversibility and further theorized that the erasure of information is fundamentally a dissipative process. Landauer posited that a fundamental energy cost is incurred by the erasure of information contained in the memory of a computation device. His theory states that to erase one binary bit of…
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In 1961, R. Landauer proposed the principle that logical irreversibility is associated with physical irreversibility and further theorized that the erasure of information is fundamentally a dissipative process. Landauer posited that a fundamental energy cost is incurred by the erasure of information contained in the memory of a computation device. His theory states that to erase one binary bit of information from a physical memory element in contact with a heat bath at a given temperature, at least kT ln(2) of heat must be dissipated from the memory into the environment, where k is the Boltzmann constant and T is the temperature. Although this connection between information theory and thermodynamics has proven to be very useful for establishing boundary limits for physical processes, Landauer principle has been a subject of some debate. Despite the theoretical controversy and fundamental importance of Landauer erasure in information technology, this phenomenon has not been experimentally explored using any practical physical implementation for digital information. Here, we report an investigation of the thermodynamic limits of the memory erasure process using nanoscale magnetic memory bits, by far the most ubiquitous digital storage technology today. Through sensitive, temperature dependent magnetometry measurements, we observed that the amount of dissipated energy is consistent with the Landauer limit during an adiabatic erasure process in nanoscale, single domain magnetic thin film islands. This result confirms the connection between information thermodynamics and physical systems and also provides a foundation for the development of practical information processing technologies that approach the fundamental limit of energy dissipation.
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Submitted 25 November, 2014;
originally announced November 2014.
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Raman signal-enhancement and broadening with graphene-coated diamond-shape nano-antennas
Authors:
Charilaos Paraskevaidis,
Tevye Kuykendall,
Mauro Melli,
Alexander Weber-Bargioni,
P. James Schuck,
Adam Schwartzberg,
Scott Dhuey,
Stefano Cabrini,
Haim Grebel
Abstract:
We used broad-band diamond-shape antennas, whose bandwidth could cover the frequency range between the pump laser and the scattered modes, in conjunction with uniformly deposited graphene test films.
We used broad-band diamond-shape antennas, whose bandwidth could cover the frequency range between the pump laser and the scattered modes, in conjunction with uniformly deposited graphene test films.
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Submitted 30 September, 2013;
originally announced October 2013.
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Device fabrication and transport measurements of FinFETs built with $^{28}$Si SOI wafers towards donor qubits in silicon
Authors:
CC Lo,
A Persaud,
S Dhuey,
D Olynick,
F Borondics,
MC Martin,
HA Bechtel,
J Bokor,
T Schenkel
Abstract:
We report fabrication of transistors in a FinFET geometry using isotopically purified silicon-28 -on-insulator (28-SOI) substrates. Donor electron spin coherence in natural silicon is limited by spectral diffusion due to the residual $^{29}$Si nuclear spin bath, making isotopically enriched nuclear spin-free $^{28}$Si substrates a promising candidate for forming spin quantum bit devices. The Fin…
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We report fabrication of transistors in a FinFET geometry using isotopically purified silicon-28 -on-insulator (28-SOI) substrates. Donor electron spin coherence in natural silicon is limited by spectral diffusion due to the residual $^{29}$Si nuclear spin bath, making isotopically enriched nuclear spin-free $^{28}$Si substrates a promising candidate for forming spin quantum bit devices. The FinFET architecture is fully compatible with single-ion implant detection for donor-based qubits, and the donor spin-state readout through electrical detection of spin resonance. We describe device processing steps and discuss results on electrical transport measurements at 0.3 K.
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Submitted 10 June, 2009;
originally announced June 2009.