Pub Date : 2024-08-07DOI: 10.1103/physrevapplied.22.024019
C.K. Safeer, Paul S. Keatley, Witold Skowroński, Jakub Mojsiejuk, Kay Yakushiji, Akio Fukushima, Shinji Yuasa, Daniel Bedau, Fèlix Casanova, Luis E. Hueso, Robert J. Hicken, Daniele Pinna, Gerrit van der Laan, Thorsten Hesjedal
Understanding the high-frequency transport characteristics of magnetic tunnel junctions (MTJs) is crucial for the development of fast-operating spintronics memories and radio frequency devices. Here, we present the study of a frequency-dependent capacitive current effect in -based MTJs and its influence on magnetization dynamics using a time-resolved magneto-optical Kerr effect technique. In our device, operating at gigahertz frequencies, we find a large displacement current of the order of mA, which does not break the tunnel barrier of the MTJ. Importantly, this current generates an Oersted field and spin-orbit torque, inducing magnetization dynamics. Our discovery holds promise for building robust MTJ devices operating under high current conditions, also highlighting the significance of capacitive impedance in high-frequency magnetotransport techniques.
{"title":"Magnetization dynamics driven by displacement currents across a magnetic tunnel junction","authors":"C.K. Safeer, Paul S. Keatley, Witold Skowroński, Jakub Mojsiejuk, Kay Yakushiji, Akio Fukushima, Shinji Yuasa, Daniel Bedau, Fèlix Casanova, Luis E. Hueso, Robert J. Hicken, Daniele Pinna, Gerrit van der Laan, Thorsten Hesjedal","doi":"10.1103/physrevapplied.22.024019","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024019","url":null,"abstract":"Understanding the high-frequency transport characteristics of magnetic tunnel junctions (MTJs) is crucial for the development of fast-operating spintronics memories and radio frequency devices. Here, we present the study of a frequency-dependent capacitive current effect in <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Co</mi><mi>Fe</mi><mi mathvariant=\"normal\">B</mi></mrow><mo>/</mo><mrow><mi>Mg</mi><mi mathvariant=\"normal\">O</mi></mrow></math>-based MTJs and its influence on magnetization dynamics using a time-resolved magneto-optical Kerr effect technique. In our device, operating at gigahertz frequencies, we find a large displacement current of the order of mA, which does not break the tunnel barrier of the MTJ. Importantly, this current generates an Oersted field and spin-orbit torque, inducing magnetization dynamics. Our discovery holds promise for building robust MTJ devices operating under high current conditions, also highlighting the significance of capacitive impedance in high-frequency magnetotransport techniques.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-07DOI: 10.1103/physrevapplied.22.024017
Taha Y. Posos, Jack Cook, Sergey V. Baryshev
Large-area carbon-nanotube (CNT) cathodes made from yarns, films, or fibers have long been promising as next-generation electron sources for high-power rf and microwave-vacuum-electronic devices. However, experimental evidence has highlighted that spatial incoherence of the electron beam produced by such cathodes impeded the progress toward high brightness CNT electron sources and their practical applications. Indeed, typically large-area CNT fibers, films, or textiles emit stochastically across their physical surface at large emission angles and with large transverse spread, meaning large emittance and hence low brightness. In this work, using high-resolution field-emission microscopy, we demonstrate that conventional electroplating of hair-thick CNT fibers followed by a femtosecond laser cutting, producing an emitter surface, solves the described incoherent emission issues extremely well. Strikingly, it was observed that the entire (within the error margin) cathode surface of a radius of approximately emitted uniformly (with no hot spots) in the direction of the applied electric field. The normalized cathode emittance, i.e., on the fiber surface, was estimated as 26- with brightness of (or ) estimated for pulsed-mode operation.
{"title":"Bright spatially coherent beam from carbon-nanotube fiber field-emission cathode","authors":"Taha Y. Posos, Jack Cook, Sergey V. Baryshev","doi":"10.1103/physrevapplied.22.024017","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024017","url":null,"abstract":"Large-area carbon-nanotube (CNT) cathodes made from yarns, films, or fibers have long been promising as next-generation electron sources for high-power rf and microwave-vacuum-electronic devices. However, experimental evidence has highlighted that spatial incoherence of the electron beam produced by such cathodes impeded the progress toward high brightness CNT electron sources and their practical applications. Indeed, typically large-area CNT fibers, films, or textiles emit stochastically across their physical surface at large emission angles and with large transverse spread, meaning large emittance and hence low brightness. In this work, using high-resolution field-emission microscopy, we demonstrate that conventional electroplating of hair-thick CNT fibers followed by a femtosecond laser cutting, producing an emitter surface, solves the described incoherent emission issues extremely well. Strikingly, it was observed that the entire (within the error margin) cathode surface of a radius of approximately <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>75</mn><mspace width=\"0.2em\"></mspace><mtext fontfamily=\"times\">μ</mtext><mtext>m</mtext></math> emitted uniformly (with no hot spots) in the direction of the applied electric field. The normalized cathode emittance, i.e., on the fiber surface, was estimated as 26-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mtext>nm</mtext><mspace width=\"0.2em\"></mspace><mtext>rad</mtext></math> with brightness of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>></mo><msup><mn>10</mn><mn>16</mn></msup><mspace width=\"0.2em\"></mspace><mtext>A</mtext><mo>/</mo><mrow><msup><mtext>m</mtext><mn>2</mn></msup><mspace width=\"0.2em\"></mspace><msup><mtext>rad</mtext><mn>2</mn></msup></mrow></math> (or <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>></mo><msup><mn>10</mn><mn>7</mn></msup><mspace width=\"0.2em\"></mspace><mrow><mi mathvariant=\"normal\">A</mi></mrow><mspace width=\"0.2em\"></mspace><msup><mrow><mi mathvariant=\"normal\">m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><mspace width=\"0.2em\"></mspace><msup><mi>sr</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace width=\"0.2em\"></mspace><msup><mrow><mi mathvariant=\"normal\">V</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>) estimated for pulsed-mode operation.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-06DOI: 10.1103/physrevapplied.22.024012
Randy Lafler, Mark L. Eickhoff, Scott C. Newey, Yamil Nieves Gonzalez, Kurt E. Stoltenberg, J. Frank Camacho, Mark A. Harris, Denis W. Oesch, Adrian J. Lewis, R. Nicholas Lanning
High-precision remote clock synchronization is crucial for many classical and quantum network applications. Evaluating options for space-Earth links, we find that traditional solutions may not produce the desired synchronization for low Earth orbits and unnecessarily complicate quantum networking architectures. Demonstrating an alternative, we use commercial off-the-shelf quantum photon sources and detection equipment to synchronize two remote clocks across our free-space testbed utilizing a method called two-way quantum time transfer (QTT). We reach picosecond-scale timing precision under very lossy and noisy channel conditions representative of daytime space-Earth links and software-emulated satellite motion. This work demonstrates how QTT is potentially relevant for daytime space-Earth quantum networking and/or providing high-precision timing in GPS-denied environments.
{"title":"Two-way quantum time transfer: a method for daytime space-Earth links","authors":"Randy Lafler, Mark L. Eickhoff, Scott C. Newey, Yamil Nieves Gonzalez, Kurt E. Stoltenberg, J. Frank Camacho, Mark A. Harris, Denis W. Oesch, Adrian J. Lewis, R. Nicholas Lanning","doi":"10.1103/physrevapplied.22.024012","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024012","url":null,"abstract":"High-precision remote clock synchronization is crucial for many classical and quantum network applications. Evaluating options for space-Earth links, we find that traditional solutions may not produce the desired synchronization for low Earth orbits and unnecessarily complicate quantum networking architectures. Demonstrating an alternative, we use commercial off-the-shelf quantum photon sources and detection equipment to synchronize two remote clocks across our free-space testbed utilizing a method called two-way quantum time transfer (QTT). We reach picosecond-scale timing precision under very lossy and noisy channel conditions representative of daytime space-Earth links and software-emulated satellite motion. This work demonstrates how QTT is potentially relevant for daytime space-Earth quantum networking and/or providing high-precision timing in GPS-denied environments.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-06DOI: 10.1103/physrevapplied.22.024013
Edward Butler-Caddle, K.D.G. Imalka Jayawardena, Anjana Wijesekara, Rebecca L. Milot, James Lloyd-Hughes
In perovskite solar cells, photovoltaic action is created by charge transport layers (CTLs) either side of the light-absorbing metal halide perovskite semiconductor. Hence, the rates for desirable charge extraction and unwanted interfacial recombination at the perovskite-CTL interfaces play a critical role for device efficiency. Here, the electrical properties of perovskite-CTL bilayer heterostructures are obtained using ultrafast terahertz and optical studies of the charge carrier dynamics after pulsed photoexcitation, combined with a physical model of charge carrier transport that includes the prominent Coulombic forces that arise after selective charge extraction into a CTL, and cross-interfacial recombination. The charge extraction velocity at the interface and the ambipolar diffusion coefficient within the perovskite are determined from the experimental decay profiles for heterostructures with three of the highest-performing CTLs, namely , PCBM and Spiro-OMeTAD. Definitive targets for the further improvement of devices are deduced: fullerenes deliver fast electron extraction, but suffer from a large rate constant for cross-interface recombination or hole extraction. Conversely, Spiro-OMeTAD exhibits slow hole extraction but does not increase the perovskite’s surface recombination rate, likely contributing to its success in solar cell devices.
{"title":"Distinguishing carrier transport and interfacial recombination at perovskite/transport-layer interfaces using ultrafast spectroscopy and numerical simulation","authors":"Edward Butler-Caddle, K.D.G. Imalka Jayawardena, Anjana Wijesekara, Rebecca L. Milot, James Lloyd-Hughes","doi":"10.1103/physrevapplied.22.024013","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024013","url":null,"abstract":"In perovskite solar cells, photovoltaic action is created by charge transport layers (CTLs) either side of the light-absorbing metal halide perovskite semiconductor. Hence, the rates for desirable charge extraction and unwanted interfacial recombination at the perovskite-CTL interfaces play a critical role for device efficiency. Here, the electrical properties of perovskite-CTL bilayer heterostructures are obtained using ultrafast terahertz and optical studies of the charge carrier dynamics after pulsed photoexcitation, combined with a physical model of charge carrier transport that includes the prominent Coulombic forces that arise after selective charge extraction into a CTL, and cross-interfacial recombination. The charge extraction velocity at the interface and the ambipolar diffusion coefficient within the perovskite are determined from the experimental decay profiles for heterostructures with three of the highest-performing CTLs, namely <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mtext>C</mtext><mn>60</mn></msub></math>, PCBM and Spiro-OMeTAD. Definitive targets for the further improvement of devices are deduced: fullerenes deliver fast electron extraction, but suffer from a large rate constant for cross-interface recombination or hole extraction. Conversely, Spiro-OMeTAD exhibits slow hole extraction but does not increase the perovskite’s surface recombination rate, likely contributing to its success in solar cell devices.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-06DOI: 10.1103/physrevapplied.22.024015
Vladimir M. Krasnov
Current-biased Josephson junctions can act as detectors of electromagnetic radiation. At optimal conditions, their sensitivity is limited by fluctuations causing stochastic switching from the superconducting to the resistive state. This work provides a quantitative description of a stochastic switching current detector, based on an underdamped Josephson junction. It is shown that activation of a Josephson plasma resonance can greatly enhance the detector responsivity in proportion to the quality factor of the junction. The ways of tuning the detector for achieving optimal operation are discussed. For realistic parameters of // tunnel junctions, the sensitivity and noise-equivalent power (NEP) can reach values of (V/W) and (), respectively. These outstanding characteristics facilitate both bolometric and single-photon detection in microwave and terahertz ranges.
{"title":"Resonant switching current detector based on underdamped Josephson junctions","authors":"Vladimir M. Krasnov","doi":"10.1103/physrevapplied.22.024015","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024015","url":null,"abstract":"Current-biased Josephson junctions can act as detectors of electromagnetic radiation. At optimal conditions, their sensitivity is limited by fluctuations causing stochastic switching from the superconducting to the resistive state. This work provides a quantitative description of a stochastic switching current detector, based on an underdamped Josephson junction. It is shown that activation of a Josephson plasma resonance can greatly enhance the detector responsivity in proportion to the quality factor of the junction. The ways of tuning the detector for achieving optimal operation are discussed. For realistic parameters of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Nb</mi></math>/<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>Al</mi><mi mathvariant=\"normal\">O</mi></mrow><mi>x</mi></msub></math>/<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Nb</mi></math> tunnel junctions, the sensitivity and noise-equivalent power (NEP) can reach values of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>S</mi><mo>≃</mo><mspace width=\"0.2em\"></mspace><mn>5</mn><mo>×</mo><msup><mn>10</mn><mn>12</mn></msup></math> (V/W) and <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>NEP</mi><mo>≃</mo><mspace width=\"0.2em\"></mspace><mn>2</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>23</mn></mrow></msup></math> (<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi>WHz</mi><mrow><mo>−</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></math>), respectively. These outstanding characteristics facilitate both bolometric and single-photon detection in microwave and terahertz ranges.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-06DOI: 10.1103/physrevapplied.22.024014
P. Michel, L. Lancia, A. Oudin, E. Kur, C. Riconda, K. Ou, V.M. Perez-Ramirez, J. Lee, M.R. Edwards
Acousto-optics consists of launching acoustic waves in a medium (usually a crystal) in order to modulate its refractive index and create a tunable optical grating. In this article, we present the theoretical basis of an alternative scheme to generate acousto-optics in a gas, where the acoustic waves are initiated by the localized absorption (and thus gas heating) of spatially modulated UV light, as was demonstrated by Michine and Yoneda [Commun. Phys. 3, 24 (2020)]. We identify the chemical reactions initiated by the absorption of UV light via the photodissociation of ozone molecules present in the gas, and calculate the resulting temperature increase in the gas as a function of space and time. Solving the Euler fluid equations shows that the modulated, isochoric heating initiates a mixed acoustic-entropy wave in the gas, whose high-amplitude density (and thus refractive index) modulation can be used to manipulate a high-power laser. We calculate that diffraction efficiencies near 100% can be obtained using only a few millimeters of gas containing a few percent ozone fraction at room temperature, with UV fluences of less than 100 —consistent with the experimental measurements. Our analysis suggests possible ways to optimize the diffraction efficiency by changing the buffer gas composition. Gases have optics damage thresholds 2–3 orders of magnitude beyond those of solids; these optical elements should therefore be able to manipulate kilojoule-class lasers.
{"title":"Photochemically induced acousto-optics in gases","authors":"P. Michel, L. Lancia, A. Oudin, E. Kur, C. Riconda, K. Ou, V.M. Perez-Ramirez, J. Lee, M.R. Edwards","doi":"10.1103/physrevapplied.22.024014","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024014","url":null,"abstract":"Acousto-optics consists of launching acoustic waves in a medium (usually a crystal) in order to modulate its refractive index and create a tunable optical grating. In this article, we present the theoretical basis of an alternative scheme to generate acousto-optics in a gas, where the acoustic waves are initiated by the localized absorption (and thus gas heating) of spatially modulated UV light, as was demonstrated by Michine and Yoneda [Commun. Phys. 3, 24 (2020)]. We identify the chemical reactions initiated by the absorption of UV light via the photodissociation of ozone molecules present in the gas, and calculate the resulting temperature increase in the gas as a function of space and time. Solving the Euler fluid equations shows that the modulated, isochoric heating initiates a mixed acoustic-entropy wave in the gas, whose high-amplitude density (and thus refractive index) modulation can be used to manipulate a high-power laser. We calculate that diffraction efficiencies near 100% can be obtained using only a few millimeters of gas containing a few percent ozone fraction at room temperature, with UV fluences of less than 100 <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mrow><mi>mJ</mi><mo>/</mo><mi>cm</mi></mrow></mrow><mn>2</mn></msup></math>—consistent with the experimental measurements. Our analysis suggests possible ways to optimize the diffraction efficiency by changing the buffer gas composition. Gases have optics damage thresholds 2–3 orders of magnitude beyond those of solids; these optical elements should therefore be able to manipulate kilojoule-class lasers.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevapplied.22.024009
Yapeng Wang, Yongcheng Ding, Francisco Andrés Cárdenas-López, Xi Chen
Solving optimization problems using variational algorithms stands out as a crucial application for noisy intermediate-scale devices. Instead of constructing gate-based quantum computers, our focus centers on designing variational quantum algorithms within the analog paradigm. This involves optimizing parameters that directly control pulses, driving quantum states toward target states without the necessity to compile a quantum circuit. In this work, we introduce pulse-based variational quantum optimization (PBVQO) as a hardware-level framework. We illustrate the framework by optimizing external fluxes on superconducting quantum interference devices, effectively driving the wave function of this specific quantum architecture to the ground state of an encoded problem Hamiltonian. Given that the performance of variational algorithms relies heavily on appropriate initial parameters, we introduce a global optimizer as a metalearning technique to tackle a simple problem. The synergy between PBVQO and metalearning provides an advantage over conventional gate-based variational algorithms.
{"title":"Pulse-based variational quantum optimization and metalearning in superconducting circuits","authors":"Yapeng Wang, Yongcheng Ding, Francisco Andrés Cárdenas-López, Xi Chen","doi":"10.1103/physrevapplied.22.024009","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024009","url":null,"abstract":"Solving optimization problems using variational algorithms stands out as a crucial application for noisy intermediate-scale devices. Instead of constructing gate-based quantum computers, our focus centers on designing variational quantum algorithms within the analog paradigm. This involves optimizing parameters that directly control pulses, driving quantum states toward target states without the necessity to compile a quantum circuit. In this work, we introduce pulse-based variational quantum optimization (PBVQO) as a hardware-level framework. We illustrate the framework by optimizing external fluxes on superconducting quantum interference devices, effectively driving the wave function of this specific quantum architecture to the ground state of an encoded problem Hamiltonian. Given that the performance of variational algorithms relies heavily on appropriate initial parameters, we introduce a global optimizer as a metalearning technique to tackle a simple problem. The synergy between PBVQO and metalearning provides an advantage over conventional gate-based variational algorithms.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevapplied.22.024011
L. Phuttitarn, B. M. Becker, R. Chinnarasu, T. M. Graham, M. Saffman
We demonstrate qubit-state measurements assisted by a supervised convolutional neural network (CNN) in a neutral-atom quantum processor. We present two CNN architectures for analyzing neutral-atom qubit readout data: a compact five-layer single-qubit CNN architecture and a six-layer multiqubit CNN architecture. We benchmark both architectures against a conventional Gaussian-threshold analysis method. In a sparse array (9- atom separation) which experiences negligible crosstalk, we have observed up to 32% and 56% error reduction for the multiqubit and single-qubit architectures, respectively, as compared to the benchmark. In a tightly spaced array (5- atom separation), which suffers from readout crosstalk, we have observed up to 43% and 32% error reduction in the multiqubit and single-qubit CNN architectures, respectively, as compared to the benchmark. By examining the correlation between the predicted states of neighboring qubits, we have found that the multiqubit CNN architecture reduces the crosstalk correlation by up to 78.5%. This work demonstrates a proof of concept for a CNN network to be implemented as a real-time readout-processing method on a neutral-atom quantum computer, enabling faster readout time and improved fidelity.
{"title":"Enhanced measurement of neutral-atom qubits with machine learning","authors":"L. Phuttitarn, B. M. Becker, R. Chinnarasu, T. M. Graham, M. Saffman","doi":"10.1103/physrevapplied.22.024011","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024011","url":null,"abstract":"We demonstrate qubit-state measurements assisted by a supervised convolutional neural network (CNN) in a neutral-atom quantum processor. We present two CNN architectures for analyzing neutral-atom qubit readout data: a compact five-layer single-qubit CNN architecture and a six-layer multiqubit CNN architecture. We benchmark both architectures against a conventional Gaussian-threshold analysis method. In a sparse array (9-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mtext fontfamily=\"times\">μ</mtext><mrow><mi mathvariant=\"normal\">m</mi></mrow></math> atom separation) which experiences negligible crosstalk, we have observed up to 32% and 56% error reduction for the multiqubit and single-qubit architectures, respectively, as compared to the benchmark. In a tightly spaced array (5-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mtext fontfamily=\"times\">μ</mtext><mrow><mi mathvariant=\"normal\">m</mi></mrow></math> atom separation), which suffers from readout crosstalk, we have observed up to 43% and 32% error reduction in the multiqubit and single-qubit CNN architectures, respectively, as compared to the benchmark. By examining the correlation between the predicted states of neighboring qubits, we have found that the multiqubit CNN architecture reduces the crosstalk correlation by up to 78.5%. This work demonstrates a proof of concept for a CNN network to be implemented as a real-time readout-processing method on a neutral-atom quantum computer, enabling faster readout time and improved fidelity.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevapplied.22.024010
Oscar Kremer, Igor Califrer, Daniel Tandeitnik, Jean Pierre von der Weid, Guilherme Temporão, Thiago Guerreiro
We implement an all-electrical controller for 3D feedback cooling of an optically levitated nanoparticle capable of reaching subkelvin temperatures for the center-of-mass motion. The controller is based on an optimal policy in which state estimation is made by delayed position measurements. The method offers a simplified path for precooling and decoupling the transverse degrees of freedom of the nanoparticle. Numerical simulations show that in an improved setup with quantum limited detection, all three axes can be cooled down to a few-phonon regime.
{"title":"All-electrical cooling of an optically levitated nanoparticle","authors":"Oscar Kremer, Igor Califrer, Daniel Tandeitnik, Jean Pierre von der Weid, Guilherme Temporão, Thiago Guerreiro","doi":"10.1103/physrevapplied.22.024010","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024010","url":null,"abstract":"We implement an all-electrical controller for 3D feedback cooling of an optically levitated nanoparticle capable of reaching subkelvin temperatures for the center-of-mass motion. The controller is based on an optimal policy in which state estimation is made by delayed position measurements. The method offers a simplified path for precooling and decoupling the transverse degrees of freedom of the nanoparticle. Numerical simulations show that in an improved setup with quantum limited detection, all three axes can be cooled down to a few-phonon regime.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevapplied.22.024005
Shuting Hou, Xikui Ma, Chao Ding, Yueheng Du, Mingwen Zhao
The emergence of two-dimensional (2D) hyperbolic materials, characterized by opposite-sign optical conductivities along two orthogonal axes within a specific band (known as the hyperbolic region), opens an avenue for optical device engineering. Broadening the hyperbolic region is essential for cutting-edge photonic applications. In this study, based on a correlation between the hyperbolic region and anisotropic electronic structures, we propose a strategic framework for identifying 2D natural hyperbolic materials (NHMs) with broadband hyperbolicity. Using this framework, we engineered a 2D lattice incorporating p and d orbitals, and discovered a series of 2D NHMs, MYZ (M = ; Y = ; and Z = ). These materials exhibit broadband hyperbolicity that extends from the near-infrared to the visible-light spectrum. We have confirmed the directional propagation of surface plasmon polaritons on these 2D materials based on Maxwell’s equations. Our findings pave the way for future exploration and practical deployment of 2D NHMs in advanced technological applications.
二维（2D）双曲面材料的特点是在特定波段（称为双曲面区域）内沿两个正交轴具有相反的光传导性，这种材料的出现为光学设备工程开辟了一条道路。拓宽双曲区对于尖端光子应用至关重要。在本研究中，基于双曲区与各向异性电子结构之间的关联，我们提出了一种战略框架，用于识别具有宽带双曲性的二维天然双曲材料（NHM）。利用这一框架，我们设计了一个包含 p 和 d 轨道的二维晶格，并发现了一系列二维天然双曲材料 MYZ（M = Co,Pd,Ru,Rh；Y = S,Se,Te；Z = Cl,Br,I）。这些材料表现出从近红外光谱到可见光光谱的宽带双曲性。我们根据麦克斯韦方程证实了表面等离子体极化子在这些二维材料上的定向传播。我们的发现为未来探索和实际部署二维 NHMs 在先进技术应用中的应用铺平了道路。
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