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Hierarchical memories: Simulating quantum LDPC codes with local gates 分层存储器：用局部门模拟量子LDPC码

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1728

Christopher A. Pattison, Anirudh Krishna, John Preskill

引用次数: 0

Partitioned Quantum Subspace Expansion 分块量子子空间展开

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1726

Tom O'Leary, Lewis W. Anderson, Dieter Jaksch, Martin Kiffner

引用次数: 0

Pauli path simulations of noisy quantum circuits beyond average case 超越平均情况的噪声量子电路泡利路径模拟

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-05-05 DOI: 10.22331/q-2025-05-05-1730

Guillermo González-García, J. Ignacio Cirac, Rahul Trivedi

{"title":"Pauli path simulations of noisy quantum circuits beyond average case","authors":"Guillermo González-García, J. Ignacio Cirac, Rahul Trivedi","doi":"10.22331/q-2025-05-05-1730","DOIUrl":"https://doi.org/10.22331/q-2025-05-05-1730","url":null,"abstract":"For random quantum circuits on $n$ qubits of depth $Theta(log n)$ with depolarizing noise, the task of sampling from the output state can be efficiently performed classically using a Pauli path method [1] . This paper aims to study the performance of this method beyond random circuits. We first consider the classical simulation of local observables in circuits composed of Clifford and T gates $unicode{x2013}$ going beyond the average case analysis, we derive sufficient conditions for simulatability in terms of the noise rate and the fraction of gates that are T gates, and show that if noise is introduced at a faster rate than T gates, the simulation becomes classically easy. As an application of this result, we study 2D QAOA circuits that attempt to find low-energy states of classical Ising models on general graphs. There, our results shows that for hard instances of the problem, which correspond to Ising model's graph being geometrically non-local, a QAOA algorithm mapped to a geometrically local circuit architecture using SWAP gates does not have any asymptotic advantage over classical algorithms if depolarized at a constant rate. Finally, we illustrate instances where the Pauli path method fails to give the correct result, and also initiate a study of the trade-off between fragility to noise and classical complexity of simulating a given quantum circuit.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"24 1","pages":"1730"},"PeriodicalIF":6.4,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143910415","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 separate quantification of state preparation errors and measurement errors on quantum computers and their mitigation 量子计算机上状态准备误差和测量误差的有效分离量化及其缓解

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