K. E. Castoria, N. R. Beysengulov, G. Koolstra, H. Byeon, E. O. Glen, M. Sammon, S. A. Lyon, J. Pollanen, D. G. Rees
Electrons trapped on the surface of cryogenic substrates (liquid helium, solid neon, or hydrogen) are an emerging platform for quantum information processing made attractive by the inherent purity of the electron environment, the scalability of trapping devices, and the predicted long lifetime of electron spin states. Here we demonstrate the spatial control and detection of single electrons above the surface of liquid helium at temperatures above 1 K. A superconducting coplanar waveguide resonator is used to read out the charge state of an electron trap defined by gate electrodes beneath the helium surface. Dispersive frequency shifts are observed as the trap is loaded with electrons, from several tens down to single electrons. These frequency shifts are in good agreement with our theoretical model that treats each electron as a classical oscillator coupled to the cavity field. This sensitive charge readout scheme can aid efforts to develop large-scale quantum processors that require the high cooling powers available in cryostats operating above 1 K.
{"title":"Sensing and Control of Single Trapped Electrons above 1 K","authors":"K. E. Castoria, N. R. Beysengulov, G. Koolstra, H. Byeon, E. O. Glen, M. Sammon, S. A. Lyon, J. Pollanen, D. G. Rees","doi":"10.1103/vcl7-73ms","DOIUrl":"https://doi.org/10.1103/vcl7-73ms","url":null,"abstract":"Electrons trapped on the surface of cryogenic substrates (liquid helium, solid neon, or hydrogen) are an emerging platform for quantum information processing made attractive by the inherent purity of the electron environment, the scalability of trapping devices, and the predicted long lifetime of electron spin states. Here we demonstrate the spatial control and detection of single electrons above the surface of liquid helium at temperatures above 1 K. A superconducting coplanar waveguide resonator is used to read out the charge state of an electron trap defined by gate electrodes beneath the helium surface. Dispersive frequency shifts are observed as the trap is loaded with electrons, from several tens down to single electrons. These frequency shifts are in good agreement with our theoretical model that treats each electron as a classical oscillator coupled to the cavity field. This sensitive charge readout scheme can aid efforts to develop large-scale quantum processors that require the high cooling powers available in cryostats operating above 1 K.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"75 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Eleonora Raimondo, Esteban Garzón, Yixin Shao, Andrea Grimaldi, Stefano Chiappini, Riccardo Tomasello, Noraica Davila-Melendez, Jordan A. Katine, Mario Carpentieri, Massimo Chiappini, Marco Lanuzza, Pedram Khalili Amiri, Giovanni Finocchio
Probabilistic computing with p-bits is emerging as a computational paradigm for machine learning and for facing combinatorial optimization problems (COPs) with the so-called probabilistic Ising machines (PIMs). From a hardware point of view, the key elements that characterize a PIM are the random number generation, the nonlinearity, the network of coupled probabilistic bits, and the energy-minimization algorithm. Regarding the energy-minimization algorithm in this work we show that PIMs using the simulated quantum annealing (SQA) schedule exhibit better performance as compared to simulated annealing and parallel tempering in solving a number of COPs, such as maximum satisfiability problems, the planted Ising problem, and the traveling salesman problem. Additionally, we design and simulate the architecture of a fully connected CMOS-based PIM that is able to run the SQA algorithm having a spin-update time of 8 ns with a power consumption of 0.22 mW. Our results also show that SQA increases the reliability and the scalability of PIMs by compensating for device variability at an algorithmic level enabling the development of their implementation combining CMOS with different technologies such as spintronics. This work shows that the characteristics of the SQA are hardware agnostic and can be applied in the codesign of any hybrid analog-digital Ising machine implementation. Our results open a promising direction for the implementation of a new generation of reliable and scalable PIMs.
{"title":"High-Performance and Reliable Probabilistic Ising Machine Based on Simulated Quantum Annealing","authors":"Eleonora Raimondo, Esteban Garzón, Yixin Shao, Andrea Grimaldi, Stefano Chiappini, Riccardo Tomasello, Noraica Davila-Melendez, Jordan A. Katine, Mario Carpentieri, Massimo Chiappini, Marco Lanuzza, Pedram Khalili Amiri, Giovanni Finocchio","doi":"10.1103/pcmz-w776","DOIUrl":"https://doi.org/10.1103/pcmz-w776","url":null,"abstract":"Probabilistic computing with p-bits is emerging as a computational paradigm for machine learning and for facing combinatorial optimization problems (COPs) with the so-called probabilistic Ising machines (PIMs). From a hardware point of view, the key elements that characterize a PIM are the random number generation, the nonlinearity, the network of coupled probabilistic bits, and the energy-minimization algorithm. Regarding the energy-minimization algorithm in this work we show that PIMs using the simulated quantum annealing (SQA) schedule exhibit better performance as compared to simulated annealing and parallel tempering in solving a number of COPs, such as maximum satisfiability problems, the planted Ising problem, and the traveling salesman problem. Additionally, we design and simulate the architecture of a fully connected CMOS-based PIM that is able to run the SQA algorithm having a spin-update time of 8 ns with a power consumption of 0.22 mW. Our results also show that SQA increases the reliability and the scalability of PIMs by compensating for device variability at an algorithmic level enabling the development of their implementation combining CMOS with different technologies such as spintronics. This work shows that the characteristics of the SQA are hardware agnostic and can be applied in the codesign of any hybrid analog-digital Ising machine implementation. Our results open a promising direction for the implementation of a new generation of reliable and scalable PIMs.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"32 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145202952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Yuxi Wang, Nianjie Liang, Xingxing Zhang, Wujuan Yan, Haiyu He, Alfredo Fiorentino, Xinwei Tao, Ang Li, Fuwei Yang, Buxuan Li, Te-Huan Liu, Jia Zhu, Wu Zhou, Wei Wang, Stefano Baroni, Lin Zhou, Bai Song
Two-dimensional (2D) crystals proved revolutionary soon after graphene was discovered in 2004. However, 2D amorphous materials down to a single layer of atoms only became accessible in 2020, and they remain largely unexplored. In particular, the thermophysical properties of amorphous materials are of great interest upon transition from 3D to 2D. Here, we probe and simulate thermal transport in monolayer amorphous carbon (MAC). An ultralow cross-plane thermal conductivity (κ) is measured for van der Waals stacked multilayers, which is comparable to that of randomly stacked graphene despite the extra disorder in MAC. This result reveals the predominant role of the weak interlayer interactions in 2D materials. Meanwhile, an unexpectedly high in-plane κ is obtained for freestanding monolayers, which is a few times higher than what is predicted by conventional wisdom for 3D amorphous carbon with a similar sp2 fraction. This observation is primarily attributed to the dimensionality-induced reduction of anharmonicity and the unique low-frequency out-of-plane vibrational modes in MAC. Amorphous materials at the 2D limit open up new avenues for understanding and manipulating heat at the atomic scale.
{"title":"Thermal Transport in a 2D Amorphous Material","authors":"Yuxi Wang, Nianjie Liang, Xingxing Zhang, Wujuan Yan, Haiyu He, Alfredo Fiorentino, Xinwei Tao, Ang Li, Fuwei Yang, Buxuan Li, Te-Huan Liu, Jia Zhu, Wu Zhou, Wei Wang, Stefano Baroni, Lin Zhou, Bai Song","doi":"10.1103/fjww-9pm3","DOIUrl":"https://doi.org/10.1103/fjww-9pm3","url":null,"abstract":"Two-dimensional (2D) crystals proved revolutionary soon after graphene was discovered in 2004. However, 2D amorphous materials down to a single layer of atoms only became accessible in 2020, and they remain largely unexplored. In particular, the thermophysical properties of amorphous materials are of great interest upon transition from 3D to 2D. Here, we probe and simulate thermal transport in monolayer amorphous carbon (MAC). An ultralow cross-plane thermal conductivity (κ</a:mi></a:math>) is measured for van der Waals stacked multilayers, which is comparable to that of randomly stacked graphene despite the extra disorder in MAC. This result reveals the predominant role of the weak interlayer interactions in 2D materials. Meanwhile, an unexpectedly high in-plane <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>κ</c:mi></c:math> is obtained for freestanding monolayers, which is a few times higher than what is predicted by conventional wisdom for 3D amorphous carbon with a similar <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mrow><e:msup><e:mrow><e:mi>sp</e:mi></e:mrow><e:mn>2</e:mn></e:msup></e:mrow></e:math> fraction. This observation is primarily attributed to the dimensionality-induced reduction of anharmonicity and the unique low-frequency out-of-plane vibrational modes in MAC. Amorphous materials at the 2D limit open up new avenues for understanding and manipulating heat at the atomic scale.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"322 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145153769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Baleegh Abdo, William Shanks, Oblesh Jinka, J. R. Rozen, Jason Orcutt
Quantum communication is needed to build powerful quantum computers and establish reliable quantum networks. At its basis lies the ability to generate and distribute entanglement to separate quantum systems, which can be used to run remote quantum operations on them or teleport quantum states from one system to another with the help of classical channels. To this end, it is useful to harness the resource of continuous-variable (CV) entanglement, since it can be efficiently and unconditionally produced by squeezing light in a nonlinear medium and can be easily manipulated, distributed, and measured using standard components. While various aspects of CV-based quantum communication have been successfully demonstrated in the optical domain, some key capabilities, such as entanglement swapping, have been lacking in the microwave domain. Here, we demonstrate three key elements of CV-based microwave quantum communication: (i) a Josephson mixer operating as a nondegenerate two-mode entangler with maximum measured logarithmic negativity EN=1.5, (ii) a quantum teleportation apparatus, capable of teleporting vacuum and coherent states with a maximum fidelity of 73%, which exceeds the 50% classical limit and is mainly limited by intermediate losses in the setup, and (iii) an entanglement-swapping system which generates entanglement between two remote noninteracting modes via entanglement-swapping operations applied to input vacuum and coherent states with maximum measured logarithmic negativity EN=0.53. Such hardware-efficient CV entanglement building blocks that are based on nondegenerate Josephson mixers could enable wide-ranging applications in modular quantum computation, quantum cryptography, and quantum communication.
{"title":"Teleportation and Entanglement Swapping of Continuous Quantum Variables of Microwave Radiation","authors":"Baleegh Abdo, William Shanks, Oblesh Jinka, J. R. Rozen, Jason Orcutt","doi":"10.1103/9cpm-kr4h","DOIUrl":"https://doi.org/10.1103/9cpm-kr4h","url":null,"abstract":"Quantum communication is needed to build powerful quantum computers and establish reliable quantum networks. At its basis lies the ability to generate and distribute entanglement to separate quantum systems, which can be used to run remote quantum operations on them or teleport quantum states from one system to another with the help of classical channels. To this end, it is useful to harness the resource of continuous-variable (CV) entanglement, since it can be efficiently and unconditionally produced by squeezing light in a nonlinear medium and can be easily manipulated, distributed, and measured using standard components. While various aspects of CV-based quantum communication have been successfully demonstrated in the optical domain, some key capabilities, such as entanglement swapping, have been lacking in the microwave domain. Here, we demonstrate three key elements of CV-based microwave quantum communication: (i) a Josephson mixer operating as a nondegenerate two-mode entangler with maximum measured logarithmic negativity E</a:mi>N</a:mi></a:msub>=</a:mo>1.5</a:mn></a:math>, (ii) a quantum teleportation apparatus, capable of teleporting vacuum and coherent states with a maximum fidelity of 73%, which exceeds the 50% classical limit and is mainly limited by intermediate losses in the setup, and (iii) an entanglement-swapping system which generates entanglement between two remote noninteracting modes via entanglement-swapping operations applied to input vacuum and coherent states with maximum measured logarithmic negativity <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:msub><c:mi>E</c:mi><c:mi>N</c:mi></c:msub><c:mo>=</c:mo><c:mn>0.53</c:mn></c:math>. Such hardware-efficient CV entanglement building blocks that are based on nondegenerate Josephson mixers could enable wide-ranging applications in modular quantum computation, quantum cryptography, and quantum communication.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"18 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145140888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Understanding the physics of the two-dimensional Hubbard model is widely believed to be a key step in achieving a full understanding of high-Tc cuprate superconductors. In recent years, progress has been made by large-scale numerical simulations at finite doping and, on the other hand, by microscopic theories able to capture the physics of individual charge carriers. In this work, we study single pairs of dopants in a cylindrical system using the density-matrix renormalization group algorithm. We identify two coexisting charge configurations that couple to the spin environment in different ways: a tightly bound configuration featuring (next-)nearest-neighbor pairs and a stripelike configuration of dopants on opposite sides of the cylinder, accompanied by a spin domain wall. Thus, we establish that the interplay between stripe order and uniform pairing, central to the models’ phases at finite doping, has its origin at the single-pair level. By interpolating between the Hubbard and the related t−J model, we are able to quantitatively understand discrepancies in the pairing properties of the two models through the three-site hopping term usually omitted from the t−J Hamiltonian. This term is closely related to a next-nearest-neighbor tunneling t′, which we observe to upset the balance between the competing stripe and pair states on the two-dopant level.
{"title":"Two-Dopant Origin of Competing Stripe and Pair Formation in Hubbard and t−J Models","authors":"Tizian Blatz, Ulrich Schollwöck, Fabian Grusdt, Annabelle Bohrdt","doi":"10.1103/dpfl-12st","DOIUrl":"https://doi.org/10.1103/dpfl-12st","url":null,"abstract":"Understanding the physics of the two-dimensional Hubbard model is widely believed to be a key step in achieving a full understanding of high-T</a:mi>c</a:mi></a:msub></a:math> cuprate superconductors. In recent years, progress has been made by large-scale numerical simulations at finite doping and, on the other hand, by microscopic theories able to capture the physics of individual charge carriers. In this work, we study single pairs of dopants in a cylindrical system using the density-matrix renormalization group algorithm. We identify two coexisting charge configurations that couple to the spin environment in different ways: a tightly bound configuration featuring (next-)nearest-neighbor pairs and a stripelike configuration of dopants on opposite sides of the cylinder, accompanied by a spin domain wall. Thus, we establish that the interplay between stripe order and uniform pairing, central to the models’ phases at finite doping, has its origin at the single-pair level. By interpolating between the Hubbard and the related <d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><d:mrow><d:mi>t</d:mi><d:mtext>−</d:mtext><d:mi>J</d:mi></d:mrow></d:math> model, we are able to quantitatively understand discrepancies in the pairing properties of the two models through the three-site hopping term usually omitted from the <f:math xmlns:f=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><f:mrow><f:mi>t</f:mi><f:mtext>−</f:mtext><f:mi>J</f:mi></f:mrow></f:math> Hamiltonian. This term is closely related to a next-nearest-neighbor tunneling <h:math xmlns:h=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><h:msup><h:mi>t</h:mi><h:mo>′</h:mo></h:msup></h:math>, which we observe to upset the balance between the competing stripe and pair states on the two-dopant level.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"15 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145133754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Lukas Brenner, Libor Caha, Xavier Coiteux-Roy, Robert Koenig
We initiate the study of state complexity for continuous-variable quantum systems. Concretely, we consider a setup with bosonic modes and auxiliary qubits, where available operations include Gaussian one- and two-mode operations and single- and two-qubit operations as well as qubit-controlled phase-space displacements. We define the (approximate) complexity of a bosonic state by the minimum size of a circuit that prepares an approximation to the state in trace distance. We propose a new circuit which prepares an approximate Gottesman-Kitaev-Preskill (GKP) state |GKPκ,Δ⟩. Here, κ−2 is the variance of the envelope, and Δ2 is the variance of the individual peaks. We show that the circuit accepts with constant probability and—conditioned on acceptance—the output state is polynomially close in (κ,Δ) to the state |GKPκ,Δ⟩. The size of our circuit is linear in (log1/κ,log1/Δ). To our knowledge, this is the first protocol for GKP-state preparation with fidelity guarantees for the prepared state. We also show converse bounds, establishing that the linear circuit-size dependence of our construction is optimal. This fully characterizes the complexity of GKP states.
{"title":"Complexity of Gottesman-Kitaev-Preskill States","authors":"Lukas Brenner, Libor Caha, Xavier Coiteux-Roy, Robert Koenig","doi":"10.1103/4ww5-4yww","DOIUrl":"https://doi.org/10.1103/4ww5-4yww","url":null,"abstract":"We initiate the study of state complexity for continuous-variable quantum systems. Concretely, we consider a setup with bosonic modes and auxiliary qubits, where available operations include Gaussian one- and two-mode operations and single- and two-qubit operations as well as qubit-controlled phase-space displacements. We define the (approximate) complexity of a bosonic state by the minimum size of a circuit that prepares an approximation to the state in trace distance. We propose a new circuit which prepares an approximate Gottesman-Kitaev-Preskill (GKP) state |</a:mo>G</a:mi>K</a:mi>P</a:mi></a:mrow>κ</a:mi>,</a:mo>Δ</a:mi></a:mrow></a:msub>⟩</a:mo></a:math>. Here, <i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><i:msup><i:mi>κ</i:mi><i:mrow><i:mo>−</i:mo><i:mn>2</i:mn></i:mrow></i:msup></i:math> is the variance of the envelope, and <k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><k:msup><k:mi mathvariant=\"normal\">Δ</k:mi><k:mn>2</k:mn></k:msup></k:math> is the variance of the individual peaks. We show that the circuit accepts with constant probability and—conditioned on acceptance—the output state is polynomially close in <n:math xmlns:n=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><n:mo stretchy=\"false\">(</n:mo><n:mi>κ</n:mi><n:mo>,</n:mo><n:mi mathvariant=\"normal\">Δ</n:mi><n:mo stretchy=\"false\">)</n:mo></n:math> to the state <s:math xmlns:s=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><s:mo stretchy=\"false\">|</s:mo><s:msub><s:mrow><s:mi mathvariant=\"sans-serif\">G</s:mi><s:mi mathvariant=\"sans-serif\">K</s:mi><s:mi mathvariant=\"sans-serif\">P</s:mi></s:mrow><s:mrow><s:mi>κ</s:mi><s:mo>,</s:mo><s:mi mathvariant=\"normal\">Δ</s:mi></s:mrow></s:msub><s:mo stretchy=\"false\">⟩</s:mo></s:math>. The size of our circuit is linear in (</ab:mo>log</ab:mi>1</ab:mn>/</ab:mo>κ</ab:mi>,</ab:mo>log</ab:mi>1</ab:mn>/</ab:mo>Δ</ab:mi>)</ab:mo></ab:math>. To our knowledge, this is the first protocol for GKP-state preparation with fidelity guarantees for the prepared state. We also show converse bounds, establishing that the linear circuit-size dependence of our construction is optimal. This fully characterizes the complexity of GKP states.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"11 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145089288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Maximilian Weimar, Lukas M. Rachbauer, Ilya Starshynov, Daniele Faccio, Linara Adilova, Dorian Bouchet, Stefan Rotter
The estimation of continuous parameters from measured data plays a central role in many fields of physics. A key tool in understanding and improving such estimation processes is the concept of Fisher information, which quantifies how information about unknown parameters propagates through a physical system and determines the ultimate limits of precision. With artificial neural networks gradually becoming an integral part of many measurement systems, it is essential to understand how they process and transmit parameter-relevant information internally. Here, we present a method to monitor the flow of Fisher information through an artificial neural network performing a parameter estimation task, tracking it from the input to the output layer. We show that optimal estimation performance corresponds to the maximal transmission of Fisher information and that training beyond this point results in information loss due to overfitting. This provides a model-free stopping criterion for network training—eliminating the need for a separate validation dataset. To demonstrate the practical relevance of our approach, we apply it to a network trained on data from an imaging experiment, highlighting its effectiveness in a realistic physical setting.
{"title":"Fisher Information Flow in Artificial Neural Networks","authors":"Maximilian Weimar, Lukas M. Rachbauer, Ilya Starshynov, Daniele Faccio, Linara Adilova, Dorian Bouchet, Stefan Rotter","doi":"10.1103/kn3z-rmm8","DOIUrl":"https://doi.org/10.1103/kn3z-rmm8","url":null,"abstract":"The estimation of continuous parameters from measured data plays a central role in many fields of physics. A key tool in understanding and improving such estimation processes is the concept of Fisher information, which quantifies how information about unknown parameters propagates through a physical system and determines the ultimate limits of precision. With artificial neural networks gradually becoming an integral part of many measurement systems, it is essential to understand how they process and transmit parameter-relevant information internally. Here, we present a method to monitor the flow of Fisher information through an artificial neural network performing a parameter estimation task, tracking it from the input to the output layer. We show that optimal estimation performance corresponds to the maximal transmission of Fisher information and that training beyond this point results in information loss due to overfitting. This provides a model-free stopping criterion for network training—eliminating the need for a separate validation dataset. To demonstrate the practical relevance of our approach, we apply it to a network trained on data from an imaging experiment, highlighting its effectiveness in a realistic physical setting.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"84 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145067976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Lucila Peralta Gavensky, Gonzalo Usaj, and Nathan Goldman
{"title":"Středa Formula for Floquet Systems: Topological Invariants and Quantized Anomalies from Cesàro Summation","authors":"Lucila Peralta Gavensky, Gonzalo Usaj, and Nathan Goldman","doi":"10.1103/b3pw-my97","DOIUrl":"https://doi.org/10.1103/b3pw-my97","url":null,"abstract":"","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"24 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145026113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Tommaso Antonelli, Marco Coraiola, David Christian Ohnmacht, Aleksandr E. Svetogorov, Deividas Sabonis, Sofieke C. ten Kate, Erik Cheah, Filip Krizek, Rüdiger Schott, Juan Carlos Cuevas, Wolfgang Belzig, Werner Wegscheider, Fabrizio Nichele
Hybrid multiterminal Josephson junctions (JJs) are expected to harbor a novel class of Andreev bound states (ABSs), including topologically nontrivial states in four-terminal devices. In these systems, topological phases emerge when ABSs depend on at least three superconducting phase differences, resulting in a three-dimensional (3D) energy spectrum characterized by Weyl nodes at zero energy. Here, we realize a four-terminal JJ in a hybrid Al/InAs heterostructure, where ABSs form a synthetic 3D band structure. We probe the energy spectrum using tunneling spectroscopy and identify spectral features associated with the formation of a tri-Andreev molecule, a bound state whose energy depends on three superconducting phases and, therefore, is able to host topological ABSs. The experimental observations are well described by a numerical model. The calculations predict the appearance of four Weyl nodes at zero energy within a gap smaller than the experimental resolution. These topological states are theoretically predicted to remain stable within an extended region of the parameter space, well accessible by our device. These findings establish an experimental foundation to study high-dimensional synthetic band structures in multiterminal JJs and to realize topological Andreev bands.
{"title":"Exploring the Energy Spectrum of a Four-Terminal Josephson Junction: Toward Topological Andreev Band Structures","authors":"Tommaso Antonelli, Marco Coraiola, David Christian Ohnmacht, Aleksandr E. Svetogorov, Deividas Sabonis, Sofieke C. ten Kate, Erik Cheah, Filip Krizek, Rüdiger Schott, Juan Carlos Cuevas, Wolfgang Belzig, Werner Wegscheider, Fabrizio Nichele","doi":"10.1103/qd3y-f912","DOIUrl":"https://doi.org/10.1103/qd3y-f912","url":null,"abstract":"Hybrid multiterminal Josephson junctions (JJs) are expected to harbor a novel class of Andreev bound states (ABSs), including topologically nontrivial states in four-terminal devices. In these systems, topological phases emerge when ABSs depend on at least three superconducting phase differences, resulting in a three-dimensional (3D) energy spectrum characterized by Weyl nodes at zero energy. Here, we realize a four-terminal JJ in a hybrid Al</a:mi>/</a:mo>InAs</a:mi></a:mrow></a:math> heterostructure, where ABSs form a synthetic 3D band structure. We probe the energy spectrum using tunneling spectroscopy and identify spectral features associated with the formation of a tri-Andreev molecule, a bound state whose energy depends on three superconducting phases and, therefore, is able to host topological ABSs. The experimental observations are well described by a numerical model. The calculations predict the appearance of four Weyl nodes at zero energy within a gap smaller than the experimental resolution. These topological states are theoretically predicted to remain stable within an extended region of the parameter space, well accessible by our device. These findings establish an experimental foundation to study high-dimensional synthetic band structures in multiterminal JJs and to realize topological Andreev bands.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"35 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145025679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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