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Quantum Solvers for Nonlinear Matrix Equations in Quantum Chemistry
Authors:
Pablo Rodenas-Ruiz,
Andrew Zhao,
Joonho Lee
Abstract:
We present a quantum algorithm for solving algebraic Riccati equations, with applications to quantum-chemical random-phase approximation (RPA) and higher-order RPA theories. Our method block-encodes stabilizing Riccati solutions via Riesz projectors onto invariant subspaces of an associated non-normal matrix, implemented using contour-integral resolvents and quantum singular value transformations.…
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We present a quantum algorithm for solving algebraic Riccati equations, with applications to quantum-chemical random-phase approximation (RPA) and higher-order RPA theories. Our method block-encodes stabilizing Riccati solutions via Riesz projectors onto invariant subspaces of an associated non-normal matrix, implemented using contour-integral resolvents and quantum singular value transformations. Applied to $m$-particle, $m$-hole RPA, our algorithm yields a block-encoding of the amplitude solution and estimates the electronic correlation-energy density with it. Under localized-orbital sparsity assumptions, the end-to-end cost scales linearly with system size and polynomially with excitation rank $m$, suggesting an exponential advantage in $m$ over plausible classical local-correlation heuristics. More broadly, this work provides a framework for quantum algorithms for nonlinear matrix equations in quantum chemistry and opens a possible route toward developing quantum algorithms for coupled-cluster theory.
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Submitted 15 May, 2026;
originally announced May 2026.
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Quantum Circuits for the Metropolis-Hastings Algorithm
Authors:
Baptiste Claudon,
Pablo Rodenas-Ruiz,
Jean-Philip Piquemal,
Pierre Monmarché
Abstract:
Szegedy's quantization of a reversible Markov chain provides a quantum walk whose spectral gap is quadratically larger than that of the classical walk. Quantum computers are therefore expected to provide a speedup of Metropolis-Hastings (MH) simulations. Existing generic methods to implement the quantum walk require coherently computing the transition probabilities of the underlying Markov kernel.…
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Szegedy's quantization of a reversible Markov chain provides a quantum walk whose spectral gap is quadratically larger than that of the classical walk. Quantum computers are therefore expected to provide a speedup of Metropolis-Hastings (MH) simulations. Existing generic methods to implement the quantum walk require coherently computing the transition probabilities of the underlying Markov kernel. However, reversible computing methods require a number of qubits that scales with the complexity of the computation. This overhead is undesirable in near-term fault-tolerant quantum computing, where few logical qubits are available. In this work, we present a Szegedy quantum walk construction which follows the classical proposal-acceptance logic, and does not require further reversible computing methods. We also compare this construction with an alternative to Szegedy's approach which also provides a quadratic gap amplification. Since each step of the quantum walks uses a constant number of proposal and acceptance steps, we expect the end-to-end quadratic speedup to hold for MH Markov Chain Monte-Carlo simulations.
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Submitted 27 May, 2026; v1 submitted 13 June, 2025;
originally announced June 2025.
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Integrated Silicon Nitride Devices via Inverse Design
Authors:
Julian L. Pita Ruiz,
Narges Dalvand,
Michaël Ménard
Abstract:
Integrated photonic devices made of silicon nitride (SiN), which can be integrated with silicon-on-insulator and III-V platforms, are expected to drive the expansion of silicon photonics technology. However, the relatively low refractive index contrast of SiN is often considered a limitation for creating compact and efficient devices. Here, we present three freeform SiN devices-a coarse wavelength…
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Integrated photonic devices made of silicon nitride (SiN), which can be integrated with silicon-on-insulator and III-V platforms, are expected to drive the expansion of silicon photonics technology. However, the relatively low refractive index contrast of SiN is often considered a limitation for creating compact and efficient devices. Here, we present three freeform SiN devices-a coarse wavelength-division multiplexer, a five-mode mode-division multiplexer, and a polarization beam splitter-while systematically benchmarking both the design capability and the fabrication repeatability and robustness of inverse-designed components. We demonstrate up to a 1200x reduction in footprint while maintaining relatively large minimum feature sizes of up to 160 nm, showing that inverse-designed SiN devices can be as compact as their silicon counterparts. These results enable high-density integration in SiN photonics and pave the way for multidimensional data transmission and quantum applications, as the inverse design technique can be applied to different SiN thicknesses and is potentially extendable to other low- and mid-index platforms.
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Submitted 15 July, 2025; v1 submitted 5 May, 2025;
originally announced May 2025.
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Frequency response limitation of heat flux meters
Authors:
I. Naveros,
Christian Ghiaus,
D. P. Ruíz
Abstract:
Heat flux meters are used for measuring the heat flux densities going through walls, usually at quasi-steady state. The limitations of heat flux meters under dynamic conditions are well documented in the literature; nonetheless there is a theoretical limitation which is mostly not considered and should be also taken into account. Since heat transfer is a dissipative process, it would be expected t…
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Heat flux meters are used for measuring the heat flux densities going through walls, usually at quasi-steady state. The limitations of heat flux meters under dynamic conditions are well documented in the literature; nonetheless there is a theoretical limitation which is mostly not considered and should be also taken into account. Since heat transfer is a dissipative process, it would be expected to obtain transfer functions which act as low pass filters. Nonetheless, this paper shows that the transfer functions modeling heat flow rate may become high pass filters, which is against the physical evidence. In order to show this theoretical limitation of the heat flux meters, the heat equation is transformed in different classes of models, from partial differential equations to transfer functions related to surface temperatures and heat flux density going through a wall.
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Submitted 6 May, 2024;
originally announced June 2024.
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Theoretical estimates of the parameters of longitudinal undular bores in PMMA bars based on their measured initial speeds
Authors:
C. G. Hooper,
K. R. Khusnutdinova,
J. M. Huntley,
P. D. Ruiz
Abstract:
We study the evolution of the longitudinal release wave that is generated by induced tensile fracture as it propagates through solid rectangular Polymethylmethacrylate (PMMA) bars of different constant cross section. High speed multi-point photoelasticity is used to register the strain wave. In all cases, oscillations develop at the bottom of the release wave that exhibit the qualitative features…
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We study the evolution of the longitudinal release wave that is generated by induced tensile fracture as it propagates through solid rectangular Polymethylmethacrylate (PMMA) bars of different constant cross section. High speed multi-point photoelasticity is used to register the strain wave. In all cases, oscillations develop at the bottom of the release wave that exhibit the qualitative features of an undular bore. The pre-strain, post-strain, strain rate of the release wave and the cross section dimensions determine the evolution of the oscillations. From the wave speed and strain rate close to the fracture site, we estimate the strain rate of the release wave as well as the growth of the amplitude and duration of the leading oscillation away from the fracture site on using formulae derived from the simple analytical solution [1] of the linearised Gardner equation (linearised near the pre-strain level at fracture), developed in our earlier work . Our estimates are then compared to experimental data, where qualitative and good semi-quantitative agreements are established.
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Submitted 22 October, 2021;
originally announced October 2021.
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Compact Dual-Polarization Silicon Integrated Couplers for Multicore Fibers
Authors:
Julian L. Pita Ruiz,
Lucas G. Rocha,
Jun Yang,
Sukru Ekin Kocabas,
Ming-Jun Li,
Ivan Aldaya,
Paulo Dainese,
Lucas H. Gabrielli
Abstract:
Compact fiber-to-chip couplers play an important role in optical interconnections, especially in data centers. However, the development of couplers has been mostly limited to standard single mode fibers, with few devices compatible with multicore and multimode fibers. Through the use of state-of-the-art optimization algorithms, we designed a compact dual-polarization coupler to interface chips and…
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Compact fiber-to-chip couplers play an important role in optical interconnections, especially in data centers. However, the development of couplers has been mostly limited to standard single mode fibers, with few devices compatible with multicore and multimode fibers. Through the use of state-of-the-art optimization algorithms, we designed a compact dual-polarization coupler to interface chips and dense multicore fibers, demonstrating, for the first time, coupling to both polarizations of all the cores, with measured coupling efficiency of $-$4.3 dB and with a 3 dB bandwidth of 48 nm. The dual-polarization coupler has footprint of 200 $μm^2$ per core, which makes it the smallest fiber-to-chip coupler experimentally demonstrated on a standard silicon-on-insulator platform.
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Submitted 7 October, 2021; v1 submitted 17 February, 2021;
originally announced February 2021.
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Development and Experimental Validation of a Viscosity Meter for Newtonian and Non-Newtonian Fluids
Authors:
Raúl O. Rojas,
Juan C. Quijano,
Claudia P. Tavera Ruiz,
Alex F. Estupiñán L
Abstract:
The study of viscosity, in the area of fluid physics at a university level, is of great importance because of the various applications that are presented in the different fields of engineering. In this work an experimental method of implementation and validation is exposed, to be able to calculate the viscosity of some newtonian and non-newtonian fluids, in which the method of a sphere that descen…
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The study of viscosity, in the area of fluid physics at a university level, is of great importance because of the various applications that are presented in the different fields of engineering. In this work an experimental method of implementation and validation is exposed, to be able to calculate the viscosity of some newtonian and non-newtonian fluids, in which the method of a sphere that descends through a fluid has been used, making Using a viscometer of our own construction, with the help of the CassyLab sensor and software of Leybold Didactics, we show the results obtained by our measuring instrument, which is intended to highlight the versatility and precision of the measuring instrument prepared by us, in addition In this work the authors want to motivate the physics laboratory teachers; to explore the use of these tools that allow you to check the topics seen in the theoretical classes. Finally, we present the hardworking results of the measurement of viscosity for different fluids, both newtonian and non-newtonian, for the latter we show the viscosity behavior as a function of temperature.
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Submitted 14 August, 2020; v1 submitted 10 August, 2020;
originally announced August 2020.
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Undular Bores Generated by Fracture
Authors:
C. G. Hooper,
P. D. Ruiz,
J. M. Huntley,
K. R. Khusnutdinova
Abstract:
Undular bores, or dispersive shock waves, are non-stationary waves propagating as oscillatory transitions between two basic states, in which the oscillatory structure gradually expands and grows in amplitude with distance travelled. We demonstrate for the first time, using high-speed pointwise photoelasticity, the generation of undular bores in solid (polymethylmethacrylate) pre-strained bars by n…
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Undular bores, or dispersive shock waves, are non-stationary waves propagating as oscillatory transitions between two basic states, in which the oscillatory structure gradually expands and grows in amplitude with distance travelled. We demonstrate for the first time, using high-speed pointwise photoelasticity, the generation of undular bores in solid (polymethylmethacrylate) pre-strained bars by natural and induced tensile fracture. For the distances relevant to our experiments, the viscoelastic extended Korteweg - de Vries (veKdV) equation is shown to provide very good agreement with the key observed experimental features for suitable choice of material parameters, while some local features at the front of the bore are also captured reasonably well by the linearisation near the nonzero pre-strain level. The experimental and theoretical approaches presented open new avenues and analytical tools for the study and application of dispersive shock waves in solids.
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Submitted 1 May, 2021; v1 submitted 14 March, 2020;
originally announced March 2020.
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Computational multifocal microscopy
Authors:
Kuan He,
Zihao Wang,
Xiang Huang,
Xiaolei Wang,
Seunghwan Yoo,
Pablo Ruiz,
Itay Gdor,
Alan Selewa,
Nicola J. Ferrier,
Norbert Scherer,
Mark Hereld,
Aggelos K. Katsaggelos,
Oliver Cossairt
Abstract:
Despite recent advances, high performance single-shot 3D microscopy remains an elusive task. By introducing designed diffractive optical elements (DOEs), one is capable of converting a microscope into a 3D "kaleidoscope", in which case the snapshot image consists of an array of tiles and each tile focuses on different depths. However, the acquired multifocal microscopic (MFM) image suffers from mu…
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Despite recent advances, high performance single-shot 3D microscopy remains an elusive task. By introducing designed diffractive optical elements (DOEs), one is capable of converting a microscope into a 3D "kaleidoscope", in which case the snapshot image consists of an array of tiles and each tile focuses on different depths. However, the acquired multifocal microscopic (MFM) image suffers from multiple sources of degradation, which prevents MFM from further applications. We propose a unifying computational framework which simplifies the imaging system and achieves 3D reconstruction via computation. Our optical configuration omits chromatic correction grating and redesigns the multifocal grating to enlarge the tracking area. Our proposed setup features only one single grating in addition to a regular microscope. The aberration correction, along with Poisson and background denoising, are incorporated in our deconvolution-based fully-automated algorithm, which requires no empirical parameter-tuning. In experiments, we achieve the spatial resolutions of $0.35$um (lateral) and $0.5$um (axial), which are comparable to the resolution that can be achieved with confocal deconvolution microscopy. We demonstrate a 3D video of moving bacteria recorded at $25$ frames per second using our proposed computational multifocal microscopy technique.
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Submitted 4 September, 2018;
originally announced September 2018.
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DEPFET active pixel detectors for a future linear $e^+e^-$ collider
Authors:
O. Alonso,
R. Casanova,
A. Dieguez,
J. Dingfelder,
T. Hemperek,
T. Kishishita amd T. Kleinohl,
M. Koch,
H. Krueger,
M. Lemarenko,
F. Luetticke,
C. Marinas,
M. Schnell,
N. Wermes,
A. Campbell,
T. Ferber,
C. Kleinwort,
C. Niebuhr,
Y. Soloviev,
M. Steder,
R. Volkenborn,
S. Yaschenko,
P. Fischer,
C. Kreidl,
I. Peric,
J. Knopf
, et al. (62 additional authors not shown)
Abstract:
The DEPFET collaboration develops highly granular, ultra-transparent active pixel detectors for high-performance vertex reconstruction at future collider experiments. The characterization of detector prototypes has proven that the key principle, the integration of a first amplification stage in a detector-grade sensor material, can provide a comfortable signal to noise ratio of over 40 for a senso…
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The DEPFET collaboration develops highly granular, ultra-transparent active pixel detectors for high-performance vertex reconstruction at future collider experiments. The characterization of detector prototypes has proven that the key principle, the integration of a first amplification stage in a detector-grade sensor material, can provide a comfortable signal to noise ratio of over 40 for a sensor thickness of 50-75 $\mathrm{\mathbf{μm}}$. ASICs have been designed and produced to operate a DEPFET pixel detector with the required read-out speed. A complete detector concept is being developed, including solutions for mechanical support, cooling and services. In this paper the status of DEPFET R & D project is reviewed in the light of the requirements of the vertex detector at a future linear $\mathbf{e^+ e^-}$ collider.
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Submitted 10 December, 2012;
originally announced December 2012.