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Gradients and frequency profiles of quantum re-uploading models 量子重载模型的梯度和频率曲线

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-14 DOI: 10.22331/q-2024-11-14-1523

Alice Barthe, Adrián Pérez-Salinas

引用次数: 0

Observational entropy with general quantum priors 具有一般量子先验的观测熵

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-14 DOI: 10.22331/q-2024-11-14-1524

Ge Bai, Dominik Šafránek, Joseph Schindler, Francesco Buscemi, Valerio Scarani

引用次数: 0

Photon-number moments and cumulants of Gaussian states 高斯态的光子数矩和累积量

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-13 DOI: 10.22331/q-2024-11-13-1521

Yanic Cardin, Nicolás Quesada

{"title":"Photon-number moments and cumulants of Gaussian states","authors":"Yanic Cardin, Nicolás Quesada","doi":"10.22331/q-2024-11-13-1521","DOIUrl":"https://doi.org/10.22331/q-2024-11-13-1521","url":null,"abstract":"We develop closed-form expressions for the moments and cumulants of Gaussian states when measured in the photon-number basis. We express the photon-number moments of a Gaussian state in terms of the loop Hafnian, a function that when applied to a $(0,1)$-matrix representing the adjacency of a graph, counts the number of its perfect matchings. Similarly, we express the photon-number cumulants in terms of the Montrealer, a newly introduced matrix function that when applied to a $(0,1)$-matrix counts the number of Hamiltonian cycles of that graph. Based on these graph-theoretic connections, we show that the calculation of photon-number moments and cumulants are #P-hard. Moreover, we provide an exponential time algorithm to calculate Montrealers (and thus cumulants), matching well-known results for Hafnians. We then demonstrate that when a uniformly lossy interferometer is fed in every input with identical single-mode Gaussian states with zero displacement, all the odd-order cumulants but the first one are zero. Finally, we employ the expressions we derive to study the distribution of cumulants up to the fourth order for different input states in a Gaussian boson sampling setup where $K$ identical states are fed into an $ell$-mode interferometer. We analyze the dependence of the cumulants as a function of the type of input state, squeezed, lossy squeezed, squashed, or thermal, and as a function of the number of non-vacuum inputs. We find that thermal states perform much worse than other classical states, such as squashed states, at mimicking the photon-number cumulants of lossy or lossless squeezed states.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"80 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600966","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}

引用次数: 0

Anomalous Floquet Phases. A resonance phenomena 异常浮凸相位共振现象

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-13 DOI: 10.22331/q-2024-11-13-1522

Álvaro Gómez-León

{"title":"Anomalous Floquet Phases. A resonance phenomena","authors":"Álvaro Gómez-León","doi":"10.22331/q-2024-11-13-1522","DOIUrl":"https://doi.org/10.22331/q-2024-11-13-1522","url":null,"abstract":"Floquet topological phases emerge when systems are periodically driven out-of-equilibrium. They gained attention due to their external control, which allows to simulate a wide variety of static systems by just tuning the external field in the high frequency regime. However, it was soon clear that their relevance goes beyond that, as for lower frequencies, anomalous phases without a static counterpart are present and the bulk-to-boundary correspondence can fail. In this work we discuss the important role of resonances in Floquet phases. For that, we present a method to find analytical solutions when the frequency of the drive matches the band gap, extending the well-known high frequency analysis of Floquet systems. With this formalism, we show that the topology of Floquet phases with resonances can be accurately captured in analytical terms. We also find a bulk-to-boundary correspondence between the number of edge states in finite systems and a set of topological invariants in different frames of reference, which crucially do not explicitly involve the micromotion. To illustrate our results, we periodically drive a SSH chain and a $pi$-flux lattice, showing that our findings remain valid in various two-band systems and in different dimensions. In addition, we notice that the competition between rotating and counter-rotating terms must be carefully treated when the undriven system is a semi-metal. To conclude, we discuss the implications to experimental setups, including the direct detection of anomalous topological phases and the measurement of their invariants.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"62 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600968","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}

引用次数: 0

Scattering wave packets of hadrons in gauge theories: Preparation on a quantum computer 量子理论中的强子散射波包：量子计算机上的准备工作

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-11 DOI: 10.22331/q-2024-11-11-1520

Zohreh Davoudi, Chung-Chun Hsieh, Saurabh V. Kadam

{"title":"Scattering wave packets of hadrons in gauge theories: Preparation on a quantum computer","authors":"Zohreh Davoudi, Chung-Chun Hsieh, Saurabh V. Kadam","doi":"10.22331/q-2024-11-11-1520","DOIUrl":"https://doi.org/10.22331/q-2024-11-11-1520","url":null,"abstract":"Quantum simulation holds promise of enabling a complete description of high-energy scattering processes rooted in gauge theories of the Standard Model. A first step in such simulations is preparation of interacting hadronic wave packets. To create the wave packets, one typically resorts to adiabatic evolution to bridge between wave packets in the free theory and those in the interacting theory, rendering the simulation resource intensive. In this work, we construct a wave-packet creation operator directly in the interacting theory to circumvent adiabatic evolution, taking advantage of resource-efficient schemes for ground-state preparation, such as variational quantum eigensolvers. By means of an ansatz for bound mesonic excitations in confining gauge theories, which is subsequently optimized using classical or quantum methods, we show that interacting mesonic wave packets can be created efficiently and accurately using digital quantum algorithms that we develop. Specifically, we obtain high-fidelity mesonic wave packets in the $Z_2$ and $U(1)$ lattice gauge theories coupled to fermionic matter in 1+1 dimensions. Our method is applicable to both perturbative and non-perturbative regimes of couplings. The wave-packet creation circuit for the case of the $Z_2$ lattice gauge theory is built and implemented on the Quantinuum $texttt{H1-1}$ trapped-ion quantum computer using 13 qubits and up to 308 entangling gates. The fidelities agree well with classical benchmark calculations after employing a simple symmetry-based noise-mitigation technique. This work serves as a step toward quantum computing scattering processes in quantum chromodynamics.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"71 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142598321","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}

引用次数: 0

Benchmarking a trapped-ion quantum computer with 30 qubits 30 量子位困离子量子计算机的基准测试

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-07 DOI: 10.22331/q-2024-11-07-1516

Jwo-Sy Chen, Erik Nielsen, Matthew Ebert, Volkan Inlek, Kenneth Wright, Vandiver Chaplin, Andrii Maksymov, Eduardo Páez, Amrit Poudel, Peter Maunz, John Gamble

{"title":"Benchmarking a trapped-ion quantum computer with 30 qubits","authors":"Jwo-Sy Chen, Erik Nielsen, Matthew Ebert, Volkan Inlek, Kenneth Wright, Vandiver Chaplin, Andrii Maksymov, Eduardo Páez, Amrit Poudel, Peter Maunz, John Gamble","doi":"10.22331/q-2024-11-07-1516","DOIUrl":"https://doi.org/10.22331/q-2024-11-07-1516","url":null,"abstract":"Quantum computers are rapidly becoming more capable, with dramatic increases in both qubit count [1] and quality [2]. Among different hardware approaches, trapped-ion quantum processors are a leading technology for quantum computing, with established high-fidelity operations and architectures with promising scaling. Here, we demonstrate and thoroughly benchmark the IonQ Forte system: configured as a single-chain 30-qubit trapped-ion quantum computer with all-to-all operations. We assess the performance of our quantum computer operation at the component level via direct randomized benchmarking (DRB) across all 30 choose 2 = 435 gate pairs. We then show the results of application-oriented [3][4] benchmarks and show that the system passes the suite of algorithmic qubit (AQ) benchmarks up to #AQ 29. Finally, we use our component-level benchmarking to build a system-level model to predict the application benchmarking data through direct simulation. While we find that the system-level model correlates with the experiment in predicting application circuit performance, we note quantitative discrepancies indicating significant out-of-model errors, leading to higher predicted performance than what is observed. This highlights that as quantum computers move toward larger and higher-quality devices, characterization becomes more challenging, suggesting future work required to push performance further.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"7 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142594650","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}

引用次数: 0

Epistemic Boundaries and Quantum Uncertainty: What Local Observers Can (Not) Predict 认识论边界与量子不确定性：局部观测者能（不能）预测什么

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-07 DOI: 10.22331/q-2024-11-07-1518

Johannes Fankhauser

引用次数: 0

Phase-space negativity as a computational resource for quantum kernel methods 作为量子核方法计算资源的相空间负性

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-07 DOI: 10.22331/q-2024-11-07-1519

Ulysse Chabaud, Roohollah Ghobadi, Salman Beigi, Saleh Rahimi-Keshari

{"title":"Phase-space negativity as a computational resource for quantum kernel methods","authors":"Ulysse Chabaud, Roohollah Ghobadi, Salman Beigi, Saleh Rahimi-Keshari","doi":"10.22331/q-2024-11-07-1519","DOIUrl":"https://doi.org/10.22331/q-2024-11-07-1519","url":null,"abstract":"Quantum kernel methods are a proposal for achieving quantum computational advantage in machine learning. They are based on a hybrid classical-quantum computation where a function called the quantum kernel is estimated by a quantum device while the rest of computation is performed classically. Quantum advantages may be achieved through this method only if the quantum kernel function cannot be estimated efficiently on a classical computer. In this paper, we provide sufficient conditions for the efficient classical estimation of quantum kernel functions for bosonic systems. These conditions are based on phase-space properties of data-encoding quantum states associated with the quantum kernels: negative volume, non-classical depth, and excess range, which are shown to be three signatures of phase-space negativity. We consider quantum optical examples involving linear-optical networks with and without adaptive non-Gaussian measurements, and investigate the effects of loss on the efficiency of the classical simulation. Our results underpin the role of the negativity in phase-space quasi-probability distributions as an essential resource in quantum machine learning based on kernel methods.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"38 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597178","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}

引用次数: 0

Asymmetry activation and its relation to coherence under permutation operation 排列操作下的不对称激活及其与一致性的关系

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-07 DOI: 10.22331/q-2024-11-07-1517

Masahito Hayashi

引用次数: 0

Maximal Elements of Quantum Communication 量子通信的最大要素

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2024-11-07 DOI: 10.22331/q-2024-11-07-1515

Teiko Heinosaari, Oskari Kerppo

引用次数: 0