Nonclassical correlation is an important concept in quantum information theory, referring to a special type of correlation that exists between quantum systems, which surpasses the scope of classical physics. In this paper, we introduce the concept of a family of information with important properties, namely the generalized Wigner-Yanase skew information, of which the famous quantum Fisher information and Wigner-Yanase skew information are special cases.We classify the local observables in the generalized Wigner-Yanase skew information into two categories (i.e., orthonormal bases and a Hermitian operator with a fixed nondegenerate spectrum), and based on this, we propose two different forms of indicators to quantify nonclassical correlations of bipartite quantum states. We have not only investigated some important properties of these two kinds of indicators but also illustrated through specific examples that they can indeed capture some nonclassical correlations. Furthermore, we find that these two types of indicators reduce to entanglement measure for bipartite pure states. Specifically, we also derive the relationship between these two indicators and the entanglement measure $I$-concurrence.
{"title":"Quantifying nonclassical correlation via the generalized Wigner-Yanase skew information","authors":"Yan Hong, Xinlan Hao, Limin Gao","doi":"arxiv-2409.11198","DOIUrl":"https://doi.org/arxiv-2409.11198","url":null,"abstract":"Nonclassical correlation is an important concept in quantum information\u0000theory, referring to a special type of correlation that exists between quantum\u0000systems, which surpasses the scope of classical physics. In this paper, we\u0000introduce the concept of a family of information with important properties,\u0000namely the generalized Wigner-Yanase skew information, of which the famous\u0000quantum Fisher information and Wigner-Yanase skew information are special\u0000cases.We classify the local observables in the generalized Wigner-Yanase skew\u0000information into two categories (i.e., orthonormal bases and a Hermitian\u0000operator with a fixed nondegenerate spectrum), and based on this, we propose\u0000two different forms of indicators to quantify nonclassical correlations of\u0000bipartite quantum states. We have not only investigated some important\u0000properties of these two kinds of indicators but also illustrated through\u0000specific examples that they can indeed capture some nonclassical correlations.\u0000Furthermore, we find that these two types of indicators reduce to entanglement\u0000measure for bipartite pure states. Specifically, we also derive the\u0000relationship between these two indicators and the entanglement measure\u0000$I$-concurrence.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The prediction of electronic structure for strongly correlated molecules represents a promising application for near-term quantum computers. Significant attention has been paid to ground state wavefunctions, but excited states of molecules are relatively unexplored. In this work, we consider the ADAPT-VQE algorithm, a single-reference approach for obtaining ground states, and its state-averaged generalization for computing multiple states at once. We demonstrate for both rectangular and linear H$_4$, as well as for BeH$_2$, that this approach, which we call MORE-ADAPT-VQE, can make better use of small excitation manifolds than an analagous method based on a single-reference ADAPT-VQE calculation, q-sc-EOM. In particular, MORE-ADAPT-VQE is able to accurately describe both avoided crossings and crossings between states of different symmetries. In addition to more accurate excited state energies, MORE-ADAPT-VQE can recover accurate transition dipole moments in situations where traditional ADAPT-VQE and q-sc-EOM struggle. These improvements suggest a promising direction toward the use of quantum computers for difficult excited state problems.
{"title":"Challenging Excited States from Adaptive Quantum Eigensolvers: Subspace Expansions vs. State-Averaged Strategies","authors":"Harper R. Grimsley, Francesco A. Evangelista","doi":"arxiv-2409.11210","DOIUrl":"https://doi.org/arxiv-2409.11210","url":null,"abstract":"The prediction of electronic structure for strongly correlated molecules\u0000represents a promising application for near-term quantum computers. Significant\u0000attention has been paid to ground state wavefunctions, but excited states of\u0000molecules are relatively unexplored. In this work, we consider the ADAPT-VQE\u0000algorithm, a single-reference approach for obtaining ground states, and its\u0000state-averaged generalization for computing multiple states at once. We\u0000demonstrate for both rectangular and linear H$_4$, as well as for BeH$_2$, that\u0000this approach, which we call MORE-ADAPT-VQE, can make better use of small\u0000excitation manifolds than an analagous method based on a single-reference\u0000ADAPT-VQE calculation, q-sc-EOM. In particular, MORE-ADAPT-VQE is able to\u0000accurately describe both avoided crossings and crossings between states of\u0000different symmetries. In addition to more accurate excited state energies,\u0000MORE-ADAPT-VQE can recover accurate transition dipole moments in situations\u0000where traditional ADAPT-VQE and q-sc-EOM struggle. These improvements suggest a\u0000promising direction toward the use of quantum computers for difficult excited\u0000state problems.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kate L. Fenwick, Jonathan Baker, Guillaume S. Thekkadath, Aaron Z. Goldberg, Khabat Heshami, Philip J. Bustard, Duncan England, Frédéric Bouchard, Benjamin Sussman
Multiphoton interference is crucial to many photonic quantum technologies. In particular, interference forms the basis of optical quantum information processing platforms and can lead to significant computational advantages. It is therefore interesting to study the interference arising from various states of light in large interferometric networks. Here, we implement a quantum walk in a highly stable, low-loss, multiport interferometer with up to 24 ultrafast time bins. This time-bin interferometer comprises a sequence of birefringent crystals which produce pulses separated by 4.3,ps, all along a single optical axis. Ultrafast Kerr gating in an optical fiber is employed to time-demultiplex the output from the quantum walk. We measure one-, two-, and three-photon interference arising from various input state combinations, including a heralded single-photon state, a thermal state, and an attenuated coherent state at one or more input ports. Our results demonstrate that ultrafast time bins are a promising platform to observe large-scale multiphoton interference.
{"title":"Multiphoton interference in a single-spatial-mode quantum walk","authors":"Kate L. Fenwick, Jonathan Baker, Guillaume S. Thekkadath, Aaron Z. Goldberg, Khabat Heshami, Philip J. Bustard, Duncan England, Frédéric Bouchard, Benjamin Sussman","doi":"arxiv-2409.11483","DOIUrl":"https://doi.org/arxiv-2409.11483","url":null,"abstract":"Multiphoton interference is crucial to many photonic quantum technologies. In\u0000particular, interference forms the basis of optical quantum information\u0000processing platforms and can lead to significant computational advantages. It\u0000is therefore interesting to study the interference arising from various states\u0000of light in large interferometric networks. Here, we implement a quantum walk\u0000in a highly stable, low-loss, multiport interferometer with up to 24 ultrafast\u0000time bins. This time-bin interferometer comprises a sequence of birefringent\u0000crystals which produce pulses separated by 4.3,ps, all along a single optical\u0000axis. Ultrafast Kerr gating in an optical fiber is employed to time-demultiplex\u0000the output from the quantum walk. We measure one-, two-, and three-photon\u0000interference arising from various input state combinations, including a\u0000heralded single-photon state, a thermal state, and an attenuated coherent state\u0000at one or more input ports. Our results demonstrate that ultrafast time bins\u0000are a promising platform to observe large-scale multiphoton interference.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Higgs boson, discovered back in 2012 through collision data at the Large Hadron Collider (LHC) by ATLAS and CMS experiments, marked a significant inflection point in High Energy Physics (HEP). Today, it's crucial to precisely measure Higgs production processes with LHC experiments in order to gain insights into the universe and find any invisible physics. To analyze the vast data that LHC experiments generate, classical machine learning has become an invaluable tool. However, classical classifiers often struggle with detecting higgs production processes, leading to incorrect labeling of Higgs Bosons. This paper aims to tackle this classification problem by investigating the use of quantum machine learning (QML).
{"title":"Evaluating Modifications to Classifiers for Identification of Higgs Bosons","authors":"Rishivarshil Nelakurti, Christopher Hill","doi":"arxiv-2409.10902","DOIUrl":"https://doi.org/arxiv-2409.10902","url":null,"abstract":"The Higgs boson, discovered back in 2012 through collision data at the Large\u0000Hadron Collider (LHC) by ATLAS and CMS experiments, marked a significant\u0000inflection point in High Energy Physics (HEP). Today, it's crucial to precisely\u0000measure Higgs production processes with LHC experiments in order to gain\u0000insights into the universe and find any invisible physics. To analyze the vast\u0000data that LHC experiments generate, classical machine learning has become an\u0000invaluable tool. However, classical classifiers often struggle with detecting\u0000higgs production processes, leading to incorrect labeling of Higgs Bosons. This\u0000paper aims to tackle this classification problem by investigating the use of\u0000quantum machine learning (QML).","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Marin, A. Fontana, V. Bellani, F. Pederiva, A. Quaranta, F. Rossella, A. Salamon, G. Salina
The Ising model with nearest-neighbor interactions on a two-dimensional (2D) square lattice is one of the simplest models for studying ferro-magnetic to para-magnetic transitions. Extensive results are available in the literature for this model, which has become a paradigm for the study of magnetic phase transitions in materials, both theoretically and numerically. After a brief review of the main results obtained with a classical computer, we show how to implement on the D- Wave quantum annealer a more complex Ising model with the addition of competing antiferromagnetic interactions between the diagonal next-to-nearest neighbors with two coupling constants J1 and J2. The dynamics of this system, owing to frustration, are richer than those of the simple Ising model and exhibit a third striped (or antiferromagnetic) phase in addition to the ferro- and para-magnetic phases. In this work, we observed all three phases on the D-Wave hardware, studied the behavior of the solution with different annealing parameters, such as the chain strength and annealing time, and showed how to identify the phase transition by varying the ratio between the ferromagnetic and antiferromagnetic couplings. The same system is studied on a classical computer, with the possibility of taking into account the temperature (fixed on D-Wave) as a free parameter and to explore the full phase diagram: some comparative conclusions with D-Wave are drawn.
{"title":"Modeling a frustrated Ising square lattice with the D-Wave Quantum Annealer","authors":"C. Marin, A. Fontana, V. Bellani, F. Pederiva, A. Quaranta, F. Rossella, A. Salamon, G. Salina","doi":"arxiv-2409.11259","DOIUrl":"https://doi.org/arxiv-2409.11259","url":null,"abstract":"The Ising model with nearest-neighbor interactions on a two-dimensional (2D)\u0000square lattice is one of the simplest models for studying ferro-magnetic to\u0000para-magnetic transitions. Extensive results are available in the literature\u0000for this model, which has become a paradigm for the study of magnetic phase\u0000transitions in materials, both theoretically and numerically. After a brief\u0000review of the main results obtained with a classical computer, we show how to\u0000implement on the D- Wave quantum annealer a more complex Ising model with the\u0000addition of competing antiferromagnetic interactions between the diagonal\u0000next-to-nearest neighbors with two coupling constants J1 and J2. The dynamics\u0000of this system, owing to frustration, are richer than those of the simple Ising\u0000model and exhibit a third striped (or antiferromagnetic) phase in addition to\u0000the ferro- and para-magnetic phases. In this work, we observed all three phases\u0000on the D-Wave hardware, studied the behavior of the solution with different\u0000annealing parameters, such as the chain strength and annealing time, and showed\u0000how to identify the phase transition by varying the ratio between the\u0000ferromagnetic and antiferromagnetic couplings. The same system is studied on a\u0000classical computer, with the possibility of taking into account the temperature\u0000(fixed on D-Wave) as a free parameter and to explore the full phase diagram:\u0000some comparative conclusions with D-Wave are drawn.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sebastian Brandhofer, Ilia Polian, Stefanie Barz, Daniel Bhatti
Highly entangled quantum states are an ingredient in numerous applications in quantum computing. However, preparing these highly entangled quantum states on currently available quantum computers at high fidelity is limited by ubiquitous errors. Besides improving the underlying technology of a quantum computer, the scale and fidelity of these entangled states in near-term quantum computers can be improved by specialized compilation methods. In this work, the compilation of quantum circuits for the preparation of highly entangled architecture-specific graph states is addressed by defining and solving a formal model. Our model incorporates information about gate cancellations, gate commutations, and accurate gate timing to determine an optimized graph state preparation circuit. Up to now, these aspects have only been considered independently of each other, typically applied to arbitrary quantum circuits. We quantify the quality of a generated state by performing stabilizer measurements and determining its fidelity. We show that our new method reduces the error when preparing a seven-qubit graph state by 3.5x on average compared to the state-of-the-art Qiskit solution. For a linear eight-qubit graph state, the error is reduced by 6.4x on average. The presented results highlight the ability of our approach to prepare higher fidelity or larger-scale graph states on gate-based quantum computing hardware.
{"title":"Hardware-Efficient Preparation of Graph States on Near-Term Quantum Computers","authors":"Sebastian Brandhofer, Ilia Polian, Stefanie Barz, Daniel Bhatti","doi":"arxiv-2409.10807","DOIUrl":"https://doi.org/arxiv-2409.10807","url":null,"abstract":"Highly entangled quantum states are an ingredient in numerous applications in\u0000quantum computing. However, preparing these highly entangled quantum states on\u0000currently available quantum computers at high fidelity is limited by ubiquitous\u0000errors. Besides improving the underlying technology of a quantum computer, the\u0000scale and fidelity of these entangled states in near-term quantum computers can\u0000be improved by specialized compilation methods. In this work, the compilation\u0000of quantum circuits for the preparation of highly entangled\u0000architecture-specific graph states is addressed by defining and solving a\u0000formal model. Our model incorporates information about gate cancellations, gate\u0000commutations, and accurate gate timing to determine an optimized graph state\u0000preparation circuit. Up to now, these aspects have only been considered\u0000independently of each other, typically applied to arbitrary quantum circuits.\u0000We quantify the quality of a generated state by performing stabilizer\u0000measurements and determining its fidelity. We show that our new method reduces\u0000the error when preparing a seven-qubit graph state by 3.5x on average compared\u0000to the state-of-the-art Qiskit solution. For a linear eight-qubit graph state,\u0000the error is reduced by 6.4x on average. The presented results highlight the\u0000ability of our approach to prepare higher fidelity or larger-scale graph states\u0000on gate-based quantum computing hardware.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pranjal Agarwal, Nada Ali, Camilla Polvara, Martin Isbjörn Trappe, Berthold-Georg Englert, Mark Hillery
Suppose you receive a sequence of qubits where each qubit is guaranteed to be in one of two pure states, but you do not know what those states are. Your task is to either determine the states or to construct a POVM (Positive Operator Valued Measure) that will discriminate them. This can be viewed as a quantum analog of unsupervised learning. A problem is that without more information, all that can be determined is the density matrix of the sequence, and, in general, density matrices can be decomposed into pure states in many different ways. To solve the problem additional information, either classical or quantum, is required. We show that if an additional copy of each qubit is supplied, that is, one receives pairs of qubits, both in the same state, rather than single qubits, the task can be accomplished. We then simulate numerically the measurement of a sequence of qubit pairs and show that the unknown states and their respective probabilities of occurrence can be found with high accuracy.
{"title":"Unsupervised state learning from pairs of states","authors":"Pranjal Agarwal, Nada Ali, Camilla Polvara, Martin Isbjörn Trappe, Berthold-Georg Englert, Mark Hillery","doi":"arxiv-2409.11120","DOIUrl":"https://doi.org/arxiv-2409.11120","url":null,"abstract":"Suppose you receive a sequence of qubits where each qubit is guaranteed to be\u0000in one of two pure states, but you do not know what those states are. Your task\u0000is to either determine the states or to construct a POVM (Positive Operator\u0000Valued Measure) that will discriminate them. This can be viewed as a quantum\u0000analog of unsupervised learning. A problem is that without more information,\u0000all that can be determined is the density matrix of the sequence, and, in\u0000general, density matrices can be decomposed into pure states in many different\u0000ways. To solve the problem additional information, either classical or quantum,\u0000is required. We show that if an additional copy of each qubit is supplied, that\u0000is, one receives pairs of qubits, both in the same state, rather than single\u0000qubits, the task can be accomplished. We then simulate numerically the\u0000measurement of a sequence of qubit pairs and show that the unknown states and\u0000their respective probabilities of occurrence can be found with high accuracy.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Yu. Dmitriev, A. V. Vasenin, S. A. Gunin, S. V. Remizov, A. A. Elistratov, W. V. Pogosov, O. V. Astafiev
A cascade of two-level superconducting artificial atoms -- a source and a probe -- strongly coupled to a semi-infinite waveguide is a promising tool for observing nontrivial phenomena in quantum nonlinear optics. The probe atom can scatter an antibunched radiation emitted from the source, thereby generating a field with specific properties. We experimentally demonstrate wave mixing between nonclassical light from the coherently cw-pumped source and another coherent wave acting on the probe. We observe unique features in the wave mixing stationary spectrum which differs from mixing spectrum of two classical waves on the probe. These features are well described by adapting the theory for a strongly coupled cascaded system of two atoms. We further analyze the theory to predict non-classical mixing spectra for various ratios of atoms' radiative constants. Both experimental and numerical results confirm the domination of multi-photon scattering process with only a single photon from the source. We evaluate entanglement of atoms in the quasistationary state and illustrate the connection between the expected second-order correlation function of source's field and wave mixing side peaks corresponding to a certain number of scattered photons.
{"title":"Direct experimental observation of sub-poissonian photon statistics by means of multi-photon scattering on a two-level system","authors":"A. Yu. Dmitriev, A. V. Vasenin, S. A. Gunin, S. V. Remizov, A. A. Elistratov, W. V. Pogosov, O. V. Astafiev","doi":"arxiv-2409.10975","DOIUrl":"https://doi.org/arxiv-2409.10975","url":null,"abstract":"A cascade of two-level superconducting artificial atoms -- a source and a\u0000probe -- strongly coupled to a semi-infinite waveguide is a promising tool for\u0000observing nontrivial phenomena in quantum nonlinear optics. The probe atom can\u0000scatter an antibunched radiation emitted from the source, thereby generating a\u0000field with specific properties. We experimentally demonstrate wave mixing\u0000between nonclassical light from the coherently cw-pumped source and another\u0000coherent wave acting on the probe. We observe unique features in the wave\u0000mixing stationary spectrum which differs from mixing spectrum of two classical\u0000waves on the probe. These features are well described by adapting the theory\u0000for a strongly coupled cascaded system of two atoms. We further analyze the\u0000theory to predict non-classical mixing spectra for various ratios of atoms'\u0000radiative constants. Both experimental and numerical results confirm the\u0000domination of multi-photon scattering process with only a single photon from\u0000the source. We evaluate entanglement of atoms in the quasistationary state and\u0000illustrate the connection between the expected second-order correlation\u0000function of source's field and wave mixing side peaks corresponding to a\u0000certain number of scattered photons.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Germaine Arend, Guanhao Huang, Armin Feist, Yujia Yang, Jan-Wilke Henke, Zheru Qiu, Hao Jeng, Arslan Sajid Raja, Rudolf Haindl, Rui Ning Wang, Tobias J. Kippenberg, Claus Ropers
Free electrons are a widespread and universal source of electromagnetic fields. The past decades witnessed ever-growing control over many aspects of electron-generated radiation, from the incoherent emission produced by X-ray tubes to the exceptional brilliance of free-electron lasers. Reduced to the elementary process of quantized energy exchange between individual electrons and the electromagnetic field, electron beams may facilitate future sources of tunable quantum light. However, the quantum features of such radiation are tied to the correlation of the particles, calling for the joint electronic and photonic state to be explored for further applications. Here, we demonstrate the coherent parametric generation of non-classical states of light by free electrons. We show that the quantized electron energy loss heralds the number of photons generated in a dielectric waveguide. In Hanbury-Brown-Twiss measurements, an electron-heralded single-photon state is revealed via antibunching intensity correlations, while two-quantum energy losses of individual electrons yield pronounced two-photon coincidences. The approach facilitates the tailored preparation of higher-number Fock and other optical quantum states based on controlled interactions with free-electron beams.
自由电子是一种广泛而普遍的电磁场源。过去几十年来，从 X 射线管产生的非相干发射到自由电子激光的非凡光彩，人们对电子产生的辐射的许多方面的控制都在不断加强。电子束被还原为单个电子与电磁场之间量子化能量交换的基本过程，可能会促进未来可调谐量子光源的发展。然而，这种辐射的量子特征与粒子的相关性息息相关，这就要求对电子和光子的联合状态进行探索，以便进一步应用。在这里，我们展示了自由电子对非经典光状态的相干参量生成。我们表明，电子能量损失的量化预示着在介质波导中产生的光子数量。在汉伯里-布朗-特维斯测量中，电子预示的单光子态通过反束强度相关性显现出来，而单个电子的双量子能量损失则产生了明显的双光子重合。这种方法有助于在控制与自由电子束的相互作用的基础上，定制制备更高数的福克态和其他光量子态。
{"title":"Electrons herald non-classical light","authors":"Germaine Arend, Guanhao Huang, Armin Feist, Yujia Yang, Jan-Wilke Henke, Zheru Qiu, Hao Jeng, Arslan Sajid Raja, Rudolf Haindl, Rui Ning Wang, Tobias J. Kippenberg, Claus Ropers","doi":"arxiv-2409.11300","DOIUrl":"https://doi.org/arxiv-2409.11300","url":null,"abstract":"Free electrons are a widespread and universal source of electromagnetic\u0000fields. The past decades witnessed ever-growing control over many aspects of\u0000electron-generated radiation, from the incoherent emission produced by X-ray\u0000tubes to the exceptional brilliance of free-electron lasers. Reduced to the\u0000elementary process of quantized energy exchange between individual electrons\u0000and the electromagnetic field, electron beams may facilitate future sources of\u0000tunable quantum light. However, the quantum features of such radiation are tied\u0000to the correlation of the particles, calling for the joint electronic and\u0000photonic state to be explored for further applications. Here, we demonstrate\u0000the coherent parametric generation of non-classical states of light by free\u0000electrons. We show that the quantized electron energy loss heralds the number\u0000of photons generated in a dielectric waveguide. In Hanbury-Brown-Twiss\u0000measurements, an electron-heralded single-photon state is revealed via\u0000antibunching intensity correlations, while two-quantum energy losses of\u0000individual electrons yield pronounced two-photon coincidences. The approach\u0000facilitates the tailored preparation of higher-number Fock and other optical\u0000quantum states based on controlled interactions with free-electron beams.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tomasz Rybotycki, Tomasz Białecki, Josep Batle, Adam Bednorz
No-signaling is a consequence of the no-communication theorem that states that bipartite systems cannot transfer information unless a communication channel exists. It is also a by-product of the assumptions of Bell theorem about quantum nonlocality. We have tested no-signaling in bipartite systems of qubits from IBM Quantum devices in extremely large statistics, resulting in significant violations. Although the time and space scales of IBM Quantum cannot in principle rule out subluminal communications, there is no obvious physical mechanism leading to signaling. The violation is also at similar level as observed in Bell tests. It is therefore mandatory to check possible technical imperfections that may cause the violation and to repeat the loophole-free Bell test at much larger statistics, in order to be ruled out definitively at strict spacelike conditions.
无信号是无通信定理的结果，该定理指出，除非存在通信通道，否则双系统无法传递信息。它也是贝尔定理关于量子非局域性假设的副产品。我们测试了来自 IBM 量子设备的量子比特双机系统在超大统计量情况下的无信号传输，结果发现严重违反了这一假设。虽然 IBM 量子的时间和空间尺度原则上不能排除亚光速通信，但没有明显的物理机制导致信号传递。因此，必须检查可能导致违规的技术缺陷，并在更大的统计量下重复无漏洞贝尔测试，以便在严格的类空间条件下明确排除违规。
{"title":"Violation of no-signaling on a public quantum computer","authors":"Tomasz Rybotycki, Tomasz Białecki, Josep Batle, Adam Bednorz","doi":"arxiv-2409.11348","DOIUrl":"https://doi.org/arxiv-2409.11348","url":null,"abstract":"No-signaling is a consequence of the no-communication theorem that states\u0000that bipartite systems cannot transfer information unless a communication channel exists. It is also a by-product of the\u0000assumptions of Bell theorem about quantum nonlocality. We have tested\u0000no-signaling in bipartite systems of qubits from IBM Quantum devices in\u0000extremely large statistics, resulting in significant violations. Although the\u0000time and space scales of IBM Quantum cannot in principle rule out subluminal\u0000communications, there is no obvious physical mechanism leading to signaling.\u0000The violation is also at similar level as observed in Bell tests. It is\u0000therefore mandatory to check possible technical imperfections that may cause\u0000the violation and to repeat the loophole-free Bell test at much larger\u0000statistics, in order to be ruled out definitively at strict spacelike\u0000conditions.","PeriodicalId":501226,"journal":{"name":"arXiv - PHYS - Quantum Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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