IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1712

Llorenç Escolà-Farràs, Florian Speelman

引用次数: 0

$mathcal{PT}$-symmetric mapping of three states and its implementation on a cloud quantum processor $mathcal{PT}$-三态对称映射及其在云量子处理器上的实现

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1716

Yaroslav Balytskyi, Yevgen Kotukh, Gennady Khalimov, Sang-Yoon Chang

{"title":"$mathcal{PT}$-symmetric mapping of three states and its implementation on a cloud quantum processor","authors":"Yaroslav Balytskyi, Yevgen Kotukh, Gennady Khalimov, Sang-Yoon Chang","doi":"10.22331/q-2025-04-18-1716","DOIUrl":"https://doi.org/10.22331/q-2025-04-18-1716","url":null,"abstract":"$mathcal{PT}$-symmetric systems have garnered significant attention due to their unconventional properties. Despite the growing interest, there remains an ongoing debate about whether these systems outperform their Hermitian counterparts in practical applications, and if so, by what metrics this performance should be measured. We developed $mathcal{PT}$-symmetric approach for mapping $N = 3$ pure qubit states to address this, implemented it using the dilation method, and demonstrated it on a superconducting quantum processor from the IBM Quantum Experience. For the first time, we derived exact expressions for the population of the post-selected $mathcal{PT}$-symmetric subspace for both $N = 2$ and $N = 3$ states. When applied to the discrimination of $N = 2$ pure states, our algorithm provides an equivalent result to the conventional unambiguous quantum state discrimination. For $N = 3$ states, our approach introduces novel capabilities not available in traditional Hermitian systems, enabling the transformation of an arbitrary set of three pure quantum states into another, at the cost of introducing an inconclusive outcome. Our algorithm has the same error rate for the attack on the three-state QKD protocol as the conventional minimum error, maximum confidence, and maximum mutual information strategies. For post-selected quantum metrology, our results provide precise conditions where $mathcal{PT}$-symmetric quantum sensors outperform their Hermitian counterparts in terms of information-cost rate. Combined with punctuated unstructured quantum database search, our method significantly reduces the qubit readout requirements at the cost of adding an ancilla, while maintaining the same average number of oracle calls as the original punctuated Grover's algorithm. Our work opens new pathways for applying $mathcal{PT}$ symmetry in quantum communications, computing, and cryptography.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"104 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847197","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

Interferometric binary phase estimations 干涉二元相位估计

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1713

Simone Roncallo, Xi Lu, Lorenzo Maccone

引用次数: 0

Optimal sampling of tensor networks targeting wave function’s fast decaying tails 针对波函数快速衰减尾的张量网络的最优采样

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1714

Marco Ballarin, Pietro Silvi, Simone Montangero, Daniel Jaschke

引用次数: 0

Bures geodesics and quantum metrology 布雷斯测地线和量子计量学

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1715

Dominique Spehner

{"title":"Bures geodesics and quantum metrology","authors":"Dominique Spehner","doi":"10.22331/q-2025-04-18-1715","DOIUrl":"https://doi.org/10.22331/q-2025-04-18-1715","url":null,"abstract":"We study the geodesics on the manifold of mixed quantum states for the Bures metric. It is shown that these geodesics correspond to physical non-Markovian evolutions of the system coupled to an ancilla. Furthermore, we argue that geodesics lead to optimal precision in single-parameter estimation in quantum metrology. More precisely, if the unknown parameter $x$ is a phase shift proportional to the time parametrizing the geodesic, the estimation error obtained by processing the data of measurements on the system is equal to the smallest error that can be achieved from joint detections on the system and ancilla, meaning that there is no information loss on this parameter in the ancilla. This error can saturate the Heisenberg bound. Reciprocally, assuming that the system-ancilla output and input states are related by a unitary $e^{-i x H}$ with $H$ a $x$-independent Hamiltonian, we show that if the error obtained from measurements on the system is equal to the minimal error obtained from joint measurements on the system and ancilla then the system evolution is given by a geodesic. In such a case, the measurement on the system bringing most information on $x$ is $x$-independent and can be determined in terms of the intersections of the geodesic with the boundary of quantum states. These results show that geodesic evolutions are of interest for high-precision detections in systems coupled to an ancilla in the absence of measurements on the ancilla.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"9 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847192","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

Efficient High-Dimensional Entangled State Analyzer with Linear Optics 高效高维线性光学纠缠态分析仪

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1711

Niv Bharos, Liubov Markovich, Johannes Borregaard

{"title":"Efficient High-Dimensional Entangled State Analyzer with Linear Optics","authors":"Niv Bharos, Liubov Markovich, Johannes Borregaard","doi":"10.22331/q-2025-04-18-1711","DOIUrl":"https://doi.org/10.22331/q-2025-04-18-1711","url":null,"abstract":"The use of higher-dimensional photonic encodings (qudits) instead of two-dimensional encodings (qubits) can improve the loss tolerance and reduce the computational resources of photonic-based quantum information processing. To harness this potential, efficient schemes for entangling operations such as the high-dimensional generalization of a linear optics Bell measurement will be required. We show how an efficient high-dimensional entangled state analyzer can be implemented with a linear optics interferometer and auxiliary photonic states. The degree of entanglement of the auxiliary state is much less than in previous protocols as quantified by an exponentially smaller Schmidt rank. In addition, the auxiliary state only occupies a single spatial mode, allowing it to be generated deterministically from a single quantum emitter coupled to a small qubit register. The reduced complexity of the auxiliary states results in a high robustness to imperfections and we show that auxiliary states with fidelities above 0.9 for qudit dimensions 4 can be generated in the presence of qubit error rates on the order of 10%. This paves the way for experimental demonstrations with current hardware.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"17 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847172","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

Eigenstate Correlations in Dual-Unitary Quantum Circuits: Partial Spectral Form Factor 双酉量子电路的本征态相关：部分谱形式因子

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-17 DOI: 10.22331/q-2025-04-17-1709

Felix Fritzsch, Maximilian F. I. Kieler, Arnd Bäcker

引用次数: 0

WaveguideQED.jl: An Efficient Framework for Simulating Non-Markovian Waveguide Quantum Electrodynamics WaveguideQED。[j]：非马尔可夫波导量子电动力学模拟的有效框架

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-17 DOI: 10.22331/q-2025-04-17-1710

Matias Bundgaard-Nielsen, Dirk Englund, Mikkel Heuck, Stefan Krastanov

引用次数: 0

Piquasso: A Photonic Quantum Computer Simulation Software Platform Piquasso：一个光子量子计算机仿真软件平台

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-15 DOI: 10.22331/q-2025-04-15-1708

Zoltán Kolarovszki, Tomasz Rybotycki, Péter Rakyta, Ágoston Kaposi, Boldizsár Poór, Szabolcs Jóczik, Dániel T. R. Nagy, Henrik Varga, Kareem H. El-Safty, Gregory Morse, Michał Oszmaniec, Tamás Kozsik, Zoltán Zimborás

引用次数: 0

Classifying fermionic states via many-body correlation measures 通过多体相关测量对费米子态进行分类

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-15 DOI: 10.22331/q-2025-04-15-1705

Mykola Semenyakin, Yevheniia Cheipesh, Yaroslav Herasymenko

{"title":"Classifying fermionic states via many-body correlation measures","authors":"Mykola Semenyakin, Yevheniia Cheipesh, Yaroslav Herasymenko","doi":"10.22331/q-2025-04-15-1705","DOIUrl":"https://doi.org/10.22331/q-2025-04-15-1705","url":null,"abstract":"Understanding the structure of quantum correlations in a many-body system is key to its computational treatment. For fermionic systems, correlations can be defined as deviations from Slater determinant states. The link between fermionic correlations and efficient computational physics methods is actively studied but remains ambiguous. We make progress in establishing this connection mathematically. In particular, we find a rigorous classification of states relative to $k$-fermion correlations, which admits a computational physics interpretation. Correlations are captured by a measure $omega_k$, a function of $k$-fermion reduced density matrix that we call twisted purity. A condition $omega_k=0$ for a given $k$ puts the state in a class $G_k$ of correlated states. Sets $G_k$ are nested in $k$, and Slater determinants correspond to $k = 1$. Classes $G_{k=O(1)}$ are shown to be physically relevant, as $omega_k$ vanishes or nearly vanishes for truncated configuration-interaction states, perturbation series around Slater determinants, and some nonperturbative eigenstates of the 1D Hubbard model. For each $k = O(1)$, we give an explicit ansatz with a polynomial number of parameters that covers all states in $G_k$. Potential applications of this ansatz and its connections to the coupled-cluster wavefunction are discussed.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"10 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143832434","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

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