IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1724

Hongye Yu, Tzu-Chieh Wei

{"title":"Efficient separate quantification of state preparation errors and measurement errors on quantum computers and their mitigation","authors":"Hongye Yu, Tzu-Chieh Wei","doi":"10.22331/q-2025-05-05-1724","DOIUrl":"https://doi.org/10.22331/q-2025-05-05-1724","url":null,"abstract":"Current noisy quantum computers have multiple types of errors, which can occur in the state preparation, measurement/readout, and gate operation, as well as intrinsic decoherence and relaxation. Partly motivated by the booming of intermediate-scale quantum processors, measurement and gate errors have been recently extensively studied, and several methods of mitigating them have been proposed and formulated in software packages (e.g., in IBM Qiskit). Despite this, the state preparation error and the procedure to quantify it have not yet been standardized, as state preparation and measurement errors are usually considered not directly separable. Inspired by a recent work of Laflamme, Lin, and Mor [15], we propose a simple and resource-efficient approach to quantify separately the state preparation and readout error rates. With these two errors separately quantified, we also propose methods to mitigate them separately, especially mitigating state preparation errors with linear (with the number of qubits) complexity. As a result of the separate mitigation, we show that the fidelity of the outcome can be improved by an order of magnitude compared to the standard measurement error mitigation scheme. We also show that the quantification and mitigation scheme is resilient against gate noise and can be immediately applied to current noisy quantum computers. To demonstrate this, we present results from cloud experiments on IBM's superconducting quantum computers. The results indicate that the state preparation error rate is also an important metric for qubit metrology that can be efficiently obtained.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"69 1","pages":"1724"},"PeriodicalIF":6.4,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143910403","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

Improving the efficiency of learning-based error mitigation 提高基于学习的错误缓解的效率

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1727

Piotr Czarnik, Michael McKerns, Andrew T. Sornborger, Lukasz Cincio

引用次数: 0

Speeding up Quantum Annealing with Engineered Dephasing 利用工程脱相加速量子退火

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1731

Mykolas Sveistrys, Josias Langbehn, Raphaël Menu, Steve Campbell, Giovanna Morigi, Christiane P. Koch

引用次数: 0

Accurately Simulating the Time Evolution of an Ising Model with Echo Verified Clifford Data Regression on a Superconducting Quantum Computer 在超导量子计算机上用回声验证Clifford数据回归精确模拟Ising模型的时间演化

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1732

Tim Weaving, Alexis Ralli, Peter J. Love, Sauro Succi, Peter V. Coveney

{"title":"Accurately Simulating the Time Evolution of an Ising Model with Echo Verified Clifford Data Regression on a Superconducting Quantum Computer","authors":"Tim Weaving, Alexis Ralli, Peter J. Love, Sauro Succi, Peter V. Coveney","doi":"10.22331/q-2025-05-05-1732","DOIUrl":"https://doi.org/10.22331/q-2025-05-05-1732","url":null,"abstract":"We present an error mitigation strategy composed of Echo Verification (EV) and Clifford Data Regression (CDR), the combination of which allows one to learn the effect of the quantum noise channel to extract error mitigated estimates for the expectation value of Pauli observables. We analyse the behaviour of the method under the depolarizing channel and derive an estimator for the depolarization rate in terms of the ancilla purity and postselection probability. We also highlight the sensitivity of this probability to noise, a potential bottleneck for the technique. We subsequently consider a more general noise channel consisting of arbitrary Pauli errors, which reveals a linear relationship between the error rates and the estimation of expectation values, suggesting the learnability of noise in EV by regression techniques. Finally, we present a practical demonstration of Echo Verified Clifford Data Regression (EVCDR) on a superconducting quantum computer and observe accurate results for the time evolution of an Ising model over spin-lattices consisting of up to 35 sites and circuit depths up to 173 entangling layers.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"115 1","pages":"1732"},"PeriodicalIF":6.4,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143910411","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

Doubly Quantum Mechanics 双量子力学

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-24 DOI: 10.22331/q-2025-04-24-1721

Vittorio D'Esposito, Giuseppe Fabiano, Domenico Frattulillo, Flavio Mercati

{"title":"Doubly Quantum Mechanics","authors":"Vittorio D'Esposito, Giuseppe Fabiano, Domenico Frattulillo, Flavio Mercati","doi":"10.22331/q-2025-04-24-1721","DOIUrl":"https://doi.org/10.22331/q-2025-04-24-1721","url":null,"abstract":"Motivated by the expectation that relativistic symmetries might acquire quantum features in Quantum Gravity, we take the first steps towards a theory of ''Doubly'' Quantum Mechanics, a modification of Quantum Mechanics in which the geometrical configurations of physical systems, measurement apparata, and reference frame transformations are themselves quantized and described by ''geometry'' states in a Hilbert space. We develop the formalism for spin-$frac{1}{2}$ measurements by promoting the group of spatial rotations $SU(2)$ to the quantum group $SU_q(2)$ and generalizing the axioms of Quantum Theory in a covariant way. As a consequence of our axioms, the notion of probability becomes a self-adjoint operator acting on the Hilbert space of geometry states, hence acquiring novel non-classical features. After introducing a suitable class of semi-classical geometry states, which describe near-to-classical geometrical configurations of physical systems, we find that probability measurements are affected, in these configurations, by intrinsic uncertainties stemming from the quantum properties of $SU_q(2)$. This feature translates into an unavoidable fuzziness for observers attempting to align their reference frames by exchanging qubits, even when the number of exchanged qubits approaches infinity, contrary to the standard $SU(2)$ case.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"1 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143872896","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

The Foliage Partition: An Easy-to-Compute LC-Invariant for Graph States 叶分割：一个易于计算的图状态的lc不变量

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-24 DOI: 10.22331/q-2025-04-24-1720

Adam Burchardt, Frederik Hahn

引用次数: 0

SuperGrad: a differentiable simulator for superconducting processors SuperGrad：超导处理器的可微分模拟器

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-24 DOI: 10.22331/q-2025-04-24-1722

Ziang Wang, Feng Wu, Hui-Hai Zhao, Xin Wan, Xiaotong Ni

引用次数: 0

Quantum dynamics as a pseudo-density matrix 伪密度矩阵的量子动力学

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-24 DOI: 10.22331/q-2025-04-24-1719

James Fullwood

引用次数: 0

Alternatives of entanglement depth and metrological entanglement criteria 可选择的纠缠深度和计量纠缠标准

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1718

Szilárd Szalay, Géza Tóth

{"title":"Alternatives of entanglement depth and metrological entanglement criteria","authors":"Szilárd Szalay, Géza Tóth","doi":"10.22331/q-2025-04-18-1718","DOIUrl":"https://doi.org/10.22331/q-2025-04-18-1718","url":null,"abstract":"We work out the general theory of one-parameter families of partial entanglement properties and the resulting entanglement depth-like quantities. Special cases of these are the depth of partitionability, the depth of producibility (or simply entanglement depth) and the depth of stretchability, which are based on one-parameter families of partial entanglement properties known earlier. We also construct some further physically meaningful properties, for instance the squareability, the toughness, the degree of freedom, and also several ones of entropic motivation. Metrological multipartite entanglement criteria with the quantum Fisher information fit naturally into this framework. Here we formulate these for the depth of squareability, which therefore turns out to be the natural choice, leading to stronger bounds than the usual entanglement depth. Namely, the quantum Fisher information turns out to provide a lower bound not only on the maximal size of entangled subsystems, but also on the average size of entangled subsystems for a random choice of elementary subsystems. We also formulate criteria with convex quantities for both cases, which are much stronger than the original ones. In particular, the quantum Fisher information puts a lower bound on the average size of entangled subsystems. We also argue that one-parameter partial entanglement properties, which carry entropic meaning, are more suitable for the purpose of defining metrological bounds.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847270","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

Lower Bounds for Unitary Property Testing with Proofs and Advice 酉性检验的下界及其证明和建议

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-18 DOI: 10.22331/q-2025-04-18-1717

Jordi Weggemans

{"title":"Lower Bounds for Unitary Property Testing with Proofs and Advice","authors":"Jordi Weggemans","doi":"10.22331/q-2025-04-18-1717","DOIUrl":"https://doi.org/10.22331/q-2025-04-18-1717","url":null,"abstract":"In unitary property testing a quantum algorithm, also known as a tester, is given query access to a black-box unitary and has to decide whether it satisfies some property. We propose a new technique for proving lower bounds on the quantum query complexity of unitary property testing and related problems, which utilises its connection to unitary channel discrimination. The main advantage of this technique is that all obtained lower bounds hold for any $mathsf{C}$-tester with $mathsf{C} subseteq mathsf{QMA}(2)/mathsf{qpoly}$, showing that even having access to both (unentangled) quantum proofs and advice does not help for many unitary property testing problems. We apply our technique to prove lower bounds for problems like quantum phase estimation, the entanglement entropy problem, quantum Gibbs sampling and more, removing all logarithmic factors in the lower bounds obtained by the sample-to-query lifting theorem of Wang and Zhang (2023). As a direct corollary, we show that there exist quantum oracles relative to which $mathsf{QMA}(2) notsupset mathsf{SBQP}$ and $mathsf{QMA}/mathsf{qpoly} notsupset mathsf{SBQP}$. The former shows that, at least in a black-box way, having unentangled quantum proofs does not help in solving problems that require high precision.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"50 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847198","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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