Pub Date : 2024-08-12DOI: 10.1103/physrevapplied.22.024033
Yun Shao, Yan Pan, Heng Wang, Ao Sun, Zhiwang Gan, Yaodi Pi, Ting Ye, Jinlu Liu, Yang Li, Yichen Zhang, Wei Huang, Bingjie Xu
Continuous-variable quantum key distribution (CV-QKD) with plug-and-play design offers a promising route in simplifying the system implementation and shows intriguing prospects for quantum access network applications. However, such a scheme makes it possible for the eavesdropper (Eve) to completely control the source, helping her to gain more information since the laser travels through the unsecured channel before being modulated, which will severely compromise the performance of the system and limit its potential application. To fight against the security loophole, we propose a passive source monitoring scheme based on a combination of beam splitter and homodyne detector, as well as source noise suppression. The corresponding entanglement-based model is established to estimate the secret key rate for the proposed scheme. We show that the performance of the plug-and-play CV-QKD system can be significantly improved by using the source monitoring scheme compared with the untrusted source model. With typical parameters, the maximum transmission distance can be promoted by more than 50%, and the secret key rate can be increased by more than 25% when the transmission distance is longer than 50 km. This study provides a feasible approach for improving the security and performance of the plug-and-play CV-QKD and holds positive potential for practical applications.
采用即插即用设计的连续可变量子密钥分配（CV-QKD）为简化系统实现提供了一条大有可为的途径，并为量子接入网络应用展示了令人感兴趣的前景。然而，这种方案使得窃听者（夏娃）有可能完全控制光源，帮助她获得更多信息，因为激光在被调制前会通过不安全的信道，这将严重影响系统的性能，限制其潜在应用。为了弥补这一安全漏洞，我们提出了一种基于分光镜和同调探测器组合以及源噪声抑制的被动源监控方案。我们建立了相应的基于纠缠的模型来估算所提方案的秘钥率。我们的研究表明，与不信任源模型相比，使用源监控方案可以显著提高即插即用 CV-QKD 系统的性能。在典型参数下，最大传输距离可提高 50%以上，当传输距离超过 50 km 时，密钥率可提高 25%以上。这项研究为提高即插即用 CV-QKD 的安全性和性能提供了一种可行的方法，具有积极的实际应用潜力。
{"title":"Source monitoring for plug-and-play continuous-variable quantum key distribution","authors":"Yun Shao, Yan Pan, Heng Wang, Ao Sun, Zhiwang Gan, Yaodi Pi, Ting Ye, Jinlu Liu, Yang Li, Yichen Zhang, Wei Huang, Bingjie Xu","doi":"10.1103/physrevapplied.22.024033","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024033","url":null,"abstract":"Continuous-variable quantum key distribution (CV-QKD) with plug-and-play design offers a promising route in simplifying the system implementation and shows intriguing prospects for quantum access network applications. However, such a scheme makes it possible for the eavesdropper (Eve) to completely control the source, helping her to gain more information since the laser travels through the unsecured channel before being modulated, which will severely compromise the performance of the system and limit its potential application. To fight against the security loophole, we propose a passive source monitoring scheme based on a combination of beam splitter and homodyne detector, as well as source noise suppression. The corresponding entanglement-based model is established to estimate the secret key rate for the proposed scheme. We show that the performance of the plug-and-play CV-QKD system can be significantly improved by using the source monitoring scheme compared with the untrusted source model. With typical parameters, the maximum transmission distance can be promoted by more than 50%, and the secret key rate can be increased by more than 25% when the transmission distance is longer than 50 km. This study provides a feasible approach for improving the security and performance of the plug-and-play CV-QKD and holds positive potential for practical applications.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949305","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 : 2024-08-12DOI: 10.1103/physrevapplied.22.024034
Bin-Bin Wang, Xiao-Jun Zhang, Jin-Hui Wu
Large dipole moments between high Rydberg states have been utilized to measure microwave electric fields based on electromagnetically induced transparency, while nonlocal Rydberg interactions are not suitably addressed yet in most relevant works. Here we adopt a mean-field superatom model to investigate the main restrictions of Rydberg microwave electrometry due to nonlocal interactions in atomic samples of appropriate densities. It is found that accurate microwave measurements can be attained in the linear regime only for dilute enough atomic samples and not too strong probe fields, which jointly determine whether Rydberg excitations are insignificant. This then leads to the critical lines of atomic density and probe intensity, below which the discrepancy between measured and real values is negligible due to vanishing Rydberg interactions, for a fixed microwave or coupling field. Our findings are instructive to identify the optimal conditions for Rydberg microwave electrometry by reaching a compromise between high precisions and high accuracies, requiring, respectively, large and small numbers of Rydberg excitations, when measuring weaker microwave fields.
{"title":"Restrictions of microwave electrometry due to nonlocal interactions in Rydberg atoms","authors":"Bin-Bin Wang, Xiao-Jun Zhang, Jin-Hui Wu","doi":"10.1103/physrevapplied.22.024034","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024034","url":null,"abstract":"Large dipole moments between high Rydberg states have been utilized to measure microwave electric fields based on electromagnetically induced transparency, while nonlocal Rydberg interactions are not suitably addressed yet in most relevant works. Here we adopt a mean-field superatom model to investigate the main restrictions of Rydberg microwave electrometry due to nonlocal interactions in atomic samples of appropriate densities. It is found that accurate microwave measurements can be attained in the linear regime only for dilute enough atomic samples and not too strong probe fields, which jointly determine whether Rydberg excitations are insignificant. This then leads to the critical lines of atomic density and probe intensity, below which the discrepancy between measured and real values is negligible due to vanishing Rydberg interactions, for a fixed microwave or coupling field. Our findings are instructive to identify the optimal conditions for Rydberg microwave electrometry by reaching a compromise between high precisions and high accuracies, requiring, respectively, large and small numbers of Rydberg excitations, when measuring weaker microwave fields.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949303","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 : 2024-08-12DOI: 10.1103/physrevapplied.22.024037
Fabrizio Mazziotti, Demetrio Logoteta, Giuseppe Iannaccone
We demonstrate that it is possible to observe enhanced shot noise in field-effect transistors, i.e., a current noise spectral density , where is the so-called “shot noise” spectral density associated to a Poissonian process of electrons traversing the channel. Whereas the effects responsible for shot-noise suppression have been broadly investigated, here we unveil the mechanism and the conditions leading to an enhancement of shot noise in field-effect transistors biased in the subthreshold or weak inversion regime, that have particular relevance in the case of short-channel metal-oxide-semiconductor field-effect transistors. The effect is due to the interplay between carrier backscattering in the channel and Coulomb repulsion among carriers. We evaluate quantitatively the effect with a semianalytical model for different types of transistors, and find a characteristic shape of the Fano factor as a function of gate bias, that enables us to look for the signature of this effect in experiments.
{"title":"Conditions for enhanced shot noise in field-effect transistors","authors":"Fabrizio Mazziotti, Demetrio Logoteta, Giuseppe Iannaccone","doi":"10.1103/physrevapplied.22.024037","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024037","url":null,"abstract":"We demonstrate that it is possible to observe enhanced shot noise in field-effect transistors, i.e., a current noise spectral density <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>S</mi><mo>></mo><msub><mi>S</mi><mi>Poisson</mi></msub></math>, where <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>S</mi><mi>Poisson</mi></msub><mo>=</mo><mn>2</mn><mi>q</mi><mi>I</mi></math> is the so-called “shot noise” spectral density associated to a Poissonian process of electrons traversing the channel. Whereas the effects responsible for shot-noise suppression have been broadly investigated, here we unveil the mechanism and the conditions leading to an enhancement of shot noise in field-effect transistors biased in the subthreshold or weak inversion regime, that have particular relevance in the case of short-channel metal-oxide-semiconductor field-effect transistors. The effect is due to the interplay between carrier backscattering in the channel and Coulomb repulsion among carriers. We evaluate quantitatively the effect with a semianalytical model for different types of transistors, and find a characteristic shape of the Fano factor <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>F</mi><mo>=</mo><mi>S</mi><mo>/</mo><msub><mi>S</mi><mi>Poisson</mi></msub></math> as a function of gate bias, that enables us to look for the signature of this effect in experiments.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949502","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 : 2024-08-12DOI: 10.1103/physrevapplied.22.024035
D. Bafia, A. Murthy, A. Grassellino, A. Romanenko
We identify a major source of quantum decoherence in three-dimensional superconducting radio-frequency (SRF) resonators and two-dimensional transmon qubits composed of oxidized niobium: oxygen vacancies in the niobium pentoxide, which drive two-level system (TLS) losses. By probing the effect of sequential in situ vacuum-baking treatments on the rf performance of bulk SRF resonators and on the oxide structure of a representative sample using TOF SIMS, we find a nonmonotonic evolution of cavity quality factor , which correlates with the interplay of vacancy generation and oxide-thickness reduction. We localize this effect to the oxide itself and present the insignificant role of diffused interstitial oxygen in the underlying by regrowing the oxide via wet oxidation, which reveals a mitigation of aggravated TLS losses. We hypothesize that such vacancies in the pentoxide serve as magnetic impurities and are a source of TLS-driven rf loss.
{"title":"Oxygen vacancies in niobium pentoxide as a source of two-level system losses in superconducting niobium","authors":"D. Bafia, A. Murthy, A. Grassellino, A. Romanenko","doi":"10.1103/physrevapplied.22.024035","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024035","url":null,"abstract":"We identify a major source of quantum decoherence in three-dimensional superconducting radio-frequency (SRF) resonators and two-dimensional transmon qubits composed of oxidized niobium: oxygen vacancies in the niobium pentoxide, which drive two-level system (TLS) losses. By probing the effect of sequential <i>in situ</i> vacuum-baking treatments on the rf performance of bulk <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Nb</mi></math> SRF resonators and on the oxide structure of a representative <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Nb</mi></math> sample using TOF SIMS, we find a nonmonotonic evolution of cavity quality factor <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Q</mi><mn>0</mn></msub></math>, which correlates with the interplay of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Nb</mi><mn>2</mn></msub><msub><mrow><mi mathvariant=\"normal\">O</mi></mrow><mn>5</mn></msub></math> vacancy generation and oxide-thickness reduction. We localize this effect to the oxide itself and present the insignificant role of diffused interstitial oxygen in the underlying <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Nb</mi></math> by regrowing the oxide via wet oxidation, which reveals a mitigation of aggravated TLS losses. We hypothesize that such vacancies in the pentoxide serve as magnetic impurities and are a source of TLS-driven rf loss.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949503","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 : 2024-08-12DOI: 10.1103/physrevapplied.22.024036
Alexander Kang-Jun Toh, McCoy W. Lim, T.S. Suraj, Xiaoye Chen, Hang Khume Tan, Royston Lim, Xuan Min Cheng, Nelson Lim, Sherry Yap, Durgesh Kumar, S.N. Piramanayagam, Pin Ho, Anjan Soumyanarayanan
Ambient magnetic skyrmions stabilized in multilayer nanostructures are of immense interest due to their relevance to magnetic tunnel junction (MTJ) devices for memory and unconventional computing applications. However, existing skyrmionic nanostructures built using conventional metallic or oxide multilayer nanodots are unable to concurrently fulfill the requirements of nanoscale skyrmion stability and all-electrical readout and manipulation. Here, we develop a few-repeat hybrid multilayer platform consisting of metallic and oxide [] components that are coupled to evolve together as a single, composite stack. Zero-field (ZF) skyrmions with sizes as small as 50 nm are stabilized in the hybrid multilayer nanodots, which are smoothly modulated by up to by varying thickness and dot sizes. Meanwhile, skyrmion multiplets are also stabilized by small bias fields. Crucially, we observe higher-order “target” skyrmions with varying magnetization rotations in moderately sized, low-anisotropy nanodots. These results provide a viable route to realize robust skyrmionic MTJs and alternative possibilities for multistate skyrmionic device concepts.
{"title":"Evolution of zero-field skyrmionic states in exchange-coupled composite multilayer nanodots","authors":"Alexander Kang-Jun Toh, McCoy W. Lim, T.S. Suraj, Xiaoye Chen, Hang Khume Tan, Royston Lim, Xuan Min Cheng, Nelson Lim, Sherry Yap, Durgesh Kumar, S.N. Piramanayagam, Pin Ho, Anjan Soumyanarayanan","doi":"10.1103/physrevapplied.22.024036","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024036","url":null,"abstract":"Ambient magnetic skyrmions stabilized in multilayer nanostructures are of immense interest due to their relevance to magnetic tunnel junction (MTJ) devices for memory and unconventional computing applications. However, existing skyrmionic nanostructures built using conventional metallic or oxide multilayer nanodots are unable to concurrently fulfill the requirements of nanoscale skyrmion stability and all-electrical readout and manipulation. Here, we develop a few-repeat hybrid multilayer platform consisting of metallic <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo stretchy=\"false\">[</mo><mi>Pt</mi><mo>/</mo><mrow><mi>Co</mi><mi mathvariant=\"normal\">B</mi></mrow><mo>/</mo><mi>Ir</mi><msub><mo stretchy=\"false\">]</mo><mn>3</mn></msub></math> and oxide [<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Pt</mi><mo>/</mo><mrow><mi>Co</mi><mi mathvariant=\"normal\">B</mi></mrow><mo>/</mo><mrow><mi>Mg</mi><mi mathvariant=\"normal\">O</mi></mrow></math>] components that are coupled to evolve together as a single, composite stack. Zero-field (ZF) skyrmions with sizes as small as 50 nm are stabilized in the hybrid multilayer nanodots, which are smoothly modulated by up to <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>2</mn><mo>×</mo></math> by varying <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Co</mi><mi mathvariant=\"normal\">B</mi></mrow></math> thickness and dot sizes. Meanwhile, skyrmion multiplets are also stabilized by small bias fields. Crucially, we observe higher-order “target” skyrmions with varying magnetization rotations in moderately sized, low-anisotropy nanodots. These results provide a viable route to realize robust skyrmionic MTJs and alternative possibilities for multistate skyrmionic device concepts.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949302","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 : 2024-08-12DOI: 10.1103/physrevapplied.22.024031
Ginevra Lautizi, Alain Studer, Marie-Christine Zdora, Fabio De Marco, Jisoo Kim, Vittorio Di Trapani, Federica Marone, Pierre Thibault, Marco Stampanoni
We present a versatile method for full-field x-ray scattering tensor tomography that is based on energy conservation and is applicable to data obtained using different wavefront modulators. Using this algorithm, we pave the way for speckle-based tensor tomography. The proposed model relies on a mathematical approach that allows tuning spatial resolution and signal sensitivity. We present the application of the algorithm to three different imaging modalities and demonstrate its potential for applications of x-ray directional dark-field imaging.
我们提出了一种基于能量守恒的全场 X 射线散射张量断层成像的通用方法，该方法适用于使用不同波前调制器获得的数据。利用这种算法，我们为基于斑点的张量断层成像铺平了道路。所提出的模型依赖于一种数学方法，可以调整空间分辨率和信号灵敏度。我们介绍了该算法在三种不同成像模式中的应用，并展示了它在 X 射线定向暗场成像中的应用潜力。
{"title":"Universal reconstruction method for x-ray scattering tensor tomography based on wavefront modulation","authors":"Ginevra Lautizi, Alain Studer, Marie-Christine Zdora, Fabio De Marco, Jisoo Kim, Vittorio Di Trapani, Federica Marone, Pierre Thibault, Marco Stampanoni","doi":"10.1103/physrevapplied.22.024031","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024031","url":null,"abstract":"We present a versatile method for full-field x-ray scattering tensor tomography that is based on energy conservation and is applicable to data obtained using different wavefront modulators. Using this algorithm, we pave the way for speckle-based tensor tomography. The proposed model relies on a mathematical approach that allows tuning spatial resolution and signal sensitivity. We present the application of the algorithm to three different imaging modalities and demonstrate its potential for applications of x-ray directional dark-field imaging.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949306","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 : 2024-08-12DOI: 10.1103/physrevapplied.22.024032
Baiyi Yu, Ralf Betzholz, Jianming Cai
Ion-ion coupling over long distances represents a highly useful resource for quantum technologies, for example, to sympathetically cool or interconnect qubits in ion-based quantum computing architectures. In this respect, the recently demonstrated wire-mediated ion-ion coupling stands due to the simplification of its trap layout and its prospects for deterministic entanglement. However, the strength of such coherent ion-wire-ion coupling is typically weak, hindering its practical utilization. Here, we propose a wire-mediated scheme for coherent ion-electron coupling. The scheme not only enables the sympathetic cooling of electrons via advanced ion-cooling techniques, but also allows promotion of the effective ion-ion coupling strength by orders of magnitudes via electron mediation. Our work thus paves a way toward quantum information processing in ion-electron hybrid quantum systems.
{"title":"Strong coherent ion-electron coupling using a wire data bus","authors":"Baiyi Yu, Ralf Betzholz, Jianming Cai","doi":"10.1103/physrevapplied.22.024032","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024032","url":null,"abstract":"Ion-ion coupling over long distances represents a highly useful resource for quantum technologies, for example, to sympathetically cool or interconnect qubits in ion-based quantum computing architectures. In this respect, the recently demonstrated wire-mediated ion-ion coupling stands due to the simplification of its trap layout and its prospects for deterministic entanglement. However, the strength of such coherent ion-wire-ion coupling is typically weak, hindering its practical utilization. Here, we propose a wire-mediated scheme for coherent ion-electron coupling. The scheme not only enables the sympathetic cooling of electrons via advanced ion-cooling techniques, but also allows promotion of the effective ion-ion coupling strength by orders of magnitudes via electron mediation. Our work thus paves a way toward quantum information processing in ion-electron hybrid quantum systems.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949304","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 : 2024-08-09DOI: 10.1103/physrevapplied.22.024027
Matthias Raba, Sébastien Triqueneaux, James Butterworth, David Schmoranzer, Emilio Barria, Jérôme Debray, Guillaume Donnier-Valentin, Thibaut Gandit, Anne Gerardin, Johannes Goupy, Olivier Tissot, Eddy Collin, Andrew Fefferman
Many laboratories routinely cool samples to 10 mK, but relatively few can cool condensed matter below 1 mK. Easy access to the microkelvin range would prove highly desirable in fields such as quantum sensors and quantum materials. Such temperatures are achieved with adiabatic nuclear demagnetization. Existing nuclear-demagnetization refrigerators (NDRs) are “single-shot,” and the recycling time is incompatible with some submillikelvin experiments. Furthermore, a high cooling power is required to overcome the excess heat load of nanowatt order on NDRs precooled by cryogen-free dilution refrigerators. We report the performance of an aluminum NDR designed for powerful cooling when part of a dual-stage continuous NDR (CNDR). Its thermal resistance is minimized to maximize the cycling rate of the CNDR and consequently its cooling power. At the same time, its susceptibility to eddy current heating is minimized. A CNDR based on two of the aluminum NDRs presented here would achieve a cooling power of approximately 40 nW at 560 less than days after cooling from room temperature, with a small offset in electronic temperature that decreases as the time-dependent heat load decays.
{"title":"Aluminum nuclear-demagnetization refrigerator for powerful continuous cooling","authors":"Matthias Raba, Sébastien Triqueneaux, James Butterworth, David Schmoranzer, Emilio Barria, Jérôme Debray, Guillaume Donnier-Valentin, Thibaut Gandit, Anne Gerardin, Johannes Goupy, Olivier Tissot, Eddy Collin, Andrew Fefferman","doi":"10.1103/physrevapplied.22.024027","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024027","url":null,"abstract":"Many laboratories routinely cool samples to 10 mK, but relatively few can cool condensed matter below 1 mK. Easy access to the microkelvin range would prove highly desirable in fields such as quantum sensors and quantum materials. Such temperatures are achieved with adiabatic nuclear demagnetization. Existing nuclear-demagnetization refrigerators (NDRs) are “single-shot,” and the recycling time is incompatible with some submillikelvin experiments. Furthermore, a high cooling power is required to overcome the excess heat load of nanowatt order on NDRs precooled by cryogen-free dilution refrigerators. We report the performance of an aluminum NDR designed for powerful cooling when part of a dual-stage continuous NDR (CNDR). Its thermal resistance is minimized to maximize the cycling rate of the CNDR and consequently its cooling power. At the same time, its susceptibility to eddy current heating is minimized. A CNDR based on two of the aluminum NDRs presented here would achieve a cooling power of approximately 40 nW at 560 <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mtext fontfamily=\"times\">μ</mtext><mrow><mi mathvariant=\"normal\">K</mi></mrow></math> less than <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>6</mn></math> days after cooling from room temperature, with a small offset in electronic temperature that decreases as the time-dependent heat load decays.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949309","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 : 2024-08-09DOI: 10.1103/physrevapplied.22.024029
Di Yu, Kun Fang
Quantum circuit mapping is a crucial process in the quantum circuit compilation pipeline, facilitating the transformation of a logical quantum circuit into a list of instructions directly executable on a target quantum system. Recent research has introduced a postcompilation step known as remapping, which seeks to reconfigure the initial circuit mapping to mitigate quantum circuit errors arising from system variability. As quantum processors continue to scale in size, the efficiency of quantum circuit mapping and the overall compilation process has become of paramount importance. In this work, we introduce a quantum circuit remapping algorithm that leverages the intrinsic symmetries in quantum processors, making it well suited for large-scale quantum systems. This algorithm identifies all topologically equivalent circuit mappings by constraining the search space using symmetries and accelerates the scoring of each mapping using vector computation. Notably, this symmetry-based-circuit-remapping algorithm exhibits linear scaling with the number of qubits in the target quantum hardware and is proven to be optimal in terms of its time complexity. Moreover, we conduct a comparative analysis against existing methods in the literature, demonstrating the superior performance of our symmetry-based method on state-of-the-art quantum hardware architectures and highlighting the practical utility of our algorithm, particularly for large-scale quantum computing.
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Pub Date : 2024-08-09DOI: 10.1103/physrevapplied.22.024030
Biel Martinez, Silvano de Franceschi, Yann-Michel Niquet
The scalability of spin-qubit devices is conditioned by qubit-to-qubit variability. Disorder in the host materials indeed affects the wave functions of the confined carriers, which leads to variations in their charge and spin properties. Charge disorder in the amorphous oxides is particularly detrimental owing to its long-range influence. Here we analyze the effects of charge traps at the semiconductor-oxide interface, which are generally believed to play a dominant role in variability. We consider multiple random distributions of these interface traps and numerically calculate their impact on the chemical potentials, detuning, and tunnel coupling of two adjacent quantum dots in heterostructure. Our results highlight the beneficial screening effect of the metal gates. The surface of the heterostructure shall, therefore, be covered as much as possible by the gates in order to limit variability. We propose an alternative layout with tip-shaped gates that maximizes the coverage of the semiconductor-oxide interface and outperforms the usual planar layout in some regimes. This highlights the importance of design in the management of device-to-device variability.
{"title":"Mitigating variability in epitaxial-heterostructure-based spin-qubit devices by optimizing gate layout","authors":"Biel Martinez, Silvano de Franceschi, Yann-Michel Niquet","doi":"10.1103/physrevapplied.22.024030","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024030","url":null,"abstract":"The scalability of spin-qubit devices is conditioned by qubit-to-qubit variability. Disorder in the host materials indeed affects the wave functions of the confined carriers, which leads to variations in their charge and spin properties. Charge disorder in the amorphous oxides is particularly detrimental owing to its long-range influence. Here we analyze the effects of charge traps at the semiconductor-oxide interface, which are generally believed to play a dominant role in variability. We consider multiple random distributions of these interface traps and numerically calculate their impact on the chemical potentials, detuning, and tunnel coupling of two adjacent quantum dots in <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Si</mi><mi>Ge</mi></mrow></math> heterostructure. Our results highlight the beneficial screening effect of the metal gates. The surface of the heterostructure shall, therefore, be covered as much as possible by the gates in order to limit variability. We propose an alternative layout with tip-shaped gates that maximizes the coverage of the semiconductor-oxide interface and outperforms the usual planar layout in some regimes. This highlights the importance of design in the management of device-to-device variability.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949307","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}
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