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Optimized Clifford Noise Reduction: Theory, Simulations and Experiments 优化Clifford降噪：理论、模拟和实验

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1829

Edwin Tham, Nicolas Delfosse

{"title":"Optimized Clifford Noise Reduction: Theory, Simulations and Experiments","authors":"Edwin Tham, Nicolas Delfosse","doi":"10.22331/q-2025-08-27-1829","DOIUrl":"https://doi.org/10.22331/q-2025-08-27-1829","url":null,"abstract":"We propose several optimizations of the CliNR partial error correction scheme which implements Clifford circuits by consuming a resource state. Errors are corrected by measuring a sequence of Pauli operators that we refer to as the verification sequence. We first propose a global optimization algorithm searching for a verification sequence resulting in a low logical error rate using tabu search. Then, we introduce a proxy for the logical error rate which is easier to evaluate and we design a two-step optimization algorithm. First, a verification sequence minimizing the proxy is computed, then this sequence is refined by reintroducing the logical error rate. Finally, we identify a large group of automorphisms of the search space which preserve the proxy and we use this symmetry to reduce the size of the search space. This results in a 168 $times$ (respectively 20,160 $times$) reduction of the size of the search space for the optimization of verification sequences with three (respectively four) Pauli operators. Our numerical simulations for 20-qubit Clifford circuits with size 400 under the ion chain model show that our optimization algorithms improve the performance of CliNR by 25% and that the two-step optimization achieves the same results as the global optimization with 64% fewer evaluations of the logical error rate. Finally, we perform experiments on a 36-qubit trapped ion quantum computer, without mid-circuit measurements, showing that the CZNR variant of CliNR is at breakeven.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"13 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905879","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

Magic Boundaries of 3D Color Codes 神奇的3D颜色代码边界

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1831

Zijian Song, Guanyu Zhu

{"title":"Magic Boundaries of 3D Color Codes","authors":"Zijian Song, Guanyu Zhu","doi":"10.22331/q-2025-08-27-1831","DOIUrl":"https://doi.org/10.22331/q-2025-08-27-1831","url":null,"abstract":"We investigate boundaries of 3D color codes and provide a systematic classification into 101 distinct boundary types, including two novel classes. The first class consists of 1 boundary and is generated by sweeping the codimension-1 (2D) $T$-domain wall across the system and attaching it to the $X$-boundary that condenses only magnetic fluxes. Since the $T$-domain wall cannot condense on the $X$-boundary, a new $textit{magic boundary}$ is produced, where the boundary stabilizers contain $XS$-stabilizers going beyond the conventional Pauli stabilizer formalism, and hence contains 'magic'. Neither electric nor magnetic excitations can condense on such a magic boundary, and only the composite of the magnetic flux and codimension-2 (1D) $S$-domain wall can condense on it, which makes the magic boundary going beyond the classification of the Lagrangian subgroup. The second class consists of 70 boundaries and is generated by sweeping the $S$-domain wall across a codimension-1 submanifold and attaching it to the boundary. This generates a codimension-2 (1D) $textit{nested boundary}$ at the intersection. We also connect these novel boundaries to their previously discovered counterpart in the $mathbb{Z}_2^3$ gauge theory, equivalent to three copies of 3D toric codes, where the $S$ and $T$ domain walls correspond to gauged symmetry-protected topological (SPT) defects. New boundaries are produced whenever the corresponding symmetry of the SPT defect remains unbroken on the boundary. Applications of the magic boundaries include implementing fault-tolerant non-Clifford logical gates, e.g., in the context of fractal topological codes.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"18 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905880","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

Optimal compilation of parametrised quantum circuits 参数化量子电路的优化编译

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1828

John van de Wetering, Richie Yeung, Tuomas Laakkonen, Aleks Kissinger

引用次数: 0

Parallel Quantum Signal Processing Via Polynomial Factorization 基于多项式分解的并行量子信号处理

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1834

John M. Martyn, Zane M. Rossi, Kevin Z. Cheng, Yuan Liu, Isaac L. Chuang

{"title":"Parallel Quantum Signal Processing Via Polynomial Factorization","authors":"John M. Martyn, Zane M. Rossi, Kevin Z. Cheng, Yuan Liu, Isaac L. Chuang","doi":"10.22331/q-2025-08-27-1834","DOIUrl":"https://doi.org/10.22331/q-2025-08-27-1834","url":null,"abstract":"Quantum signal processing (QSP) is a methodology for constructing polynomial transformations of a linear operator encoded in a unitary. Applied to an encoding of a state $rho$, QSP enables the evaluation of nonlinear functions of the form $text{tr}(P(rho))$ for a polynomial $P(x)$, which encompasses relevant properties like entropies and fidelity. However, QSP is a sequential algorithm: implementing a degree-$d$ polynomial necessitates $d$ queries to the encoding, equating to a query depth $d$. Here, we reduce the depth of these property estimation algorithms by developing Parallel Quantum Signal Processing. Our algorithm parallelizes the computation of $text{tr} (P(rho))$ over $k$ systems and reduces the query depth to $d/k$, thus enabling a family of time-space tradeoffs for QSP. This furnishes a property estimation algorithm suitable for distributed quantum computers, and is realized at the expense of increasing the number of measurements by a factor $O( text{poly}(d) 2^{O(k)} )$. We achieve this result by factorizing $P(x)$ into a product of $k$ smaller polynomials of degree $O(d/k)$, which are each implemented in parallel with QSP, and subsequently multiplied together with a swap test to reconstruct $P(x)$. We characterize the achievable class of polynomials by appealing to the fundamental theorem of algebra, and demonstrate application to canonical problems including entropy estimation and partition function evaluation.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"24 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905883","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

Estimating quantum Markov chains using coherent absorber post-processing and pattern counting estimator 利用相干吸收后处理和模式计数估计估计量子马尔可夫链

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1835

Federico Girotti, Alfred Godley, Madalin Guta

{"title":"Estimating quantum Markov chains using coherent absorber post-processing and pattern counting estimator","authors":"Federico Girotti, Alfred Godley, Madalin Guta","doi":"10.22331/q-2025-08-27-1835","DOIUrl":"https://doi.org/10.22331/q-2025-08-27-1835","url":null,"abstract":"We propose a two step strategy for estimating one-dimensional dynamical parameters of a quantum Markov chain, which involves quantum post-processing the output using a coherent quantum absorber and a \"pattern counting'' estimator computed as a simple additive functional of the outcomes trajectory produced by sequential, identical measurements on the output units. We provide strong theoretical and numerical evidence that the estimator achieves the quantum Cramer-Rao bound in the limit of large output size. Our estimation method is underpinned by an asymptotic theory of translationally invariant modes (TIMs) built as averages of shifted tensor products of output operators, labelled by binary patterns. For large times, the TIMs form a bosonic algebra and the output state approaches a joint coherent state of the TIMs whose amplitude depends linearly on the mismatch between system and absorber parameters. Moreover, in the asymptotic regime the TIMs capture the full quantum Fisher information of the output state. While directly probing the TIMs' quadratures seems impractical, we show that the standard sequential measurement is an effective joint measurement of all the TIMs number operators; indeed, we show that counts of different binary patterns extracted from the measurement trajectory have the expected joint Poisson distribution. Together with the displaced-null methodology of [1] this provides a computationally efficient estimator which only depends on the total number of patterns. This opens the way for similar estimation strategies in continuous-time dynamics, expanding the results of [2].","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"28 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905884","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

Estimating Eigenenergies from Quantum Dynamics: A Unified Noise-Resilient Measurement-Driven Approach 从量子动力学估计特征能量：一种统一的噪声弹性测量驱动方法

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1836

Yizhi Shen, Daan Camps, Aaron Szasz, Siva Darbha, Katherine Klymko, David B. Williams--Young, Norm M. Tubman, Roel Van Beeumen

{"title":"Estimating Eigenenergies from Quantum Dynamics: A Unified Noise-Resilient Measurement-Driven Approach","authors":"Yizhi Shen, Daan Camps, Aaron Szasz, Siva Darbha, Katherine Klymko, David B. Williams--Young, Norm M. Tubman, Roel Van Beeumen","doi":"10.22331/q-2025-08-27-1836","DOIUrl":"https://doi.org/10.22331/q-2025-08-27-1836","url":null,"abstract":"Ground state energy estimation in physical, chemical, and materials sciences is one of the most promising applications of quantum computing. In this work, we introduce a new hybrid approach that finds the eigenenergies by collecting real-time measurements and post-processing them using the machinery of dynamic mode decomposition (DMD). From the perspective of quantum dynamics, we establish that our approach can be formally understood as a stable variational method on the function space of observables available from a quantum many-body system. We also provide strong theoretical and numerical evidence that our method converges rapidly even in the presence of a large degree of perturbative noise, and show that the method bears an isomorphism to robust matrix factorization methods developed independently across various scientific communities. Our numerical benchmarks on spin and molecular systems demonstrate an accelerated convergence and a favorable resource reduction over state-of-the-art algorithms. The DMD-centric strategy can systematically mitigate noise and stands out as a leading hybrid quantum-classical eigensolver.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"53 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905885","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

Noise-robust proofs of quantum network nonlocality 量子网络非局域性的噪声鲁棒性证明

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-27 DOI: 10.22331/q-2025-08-27-1830

Sadra Boreiri, Bora Ulu, Nicolas Brunner, Pavel Sekatski

{"title":"Noise-robust proofs of quantum network nonlocality","authors":"Sadra Boreiri, Bora Ulu, Nicolas Brunner, Pavel Sekatski","doi":"10.22331/q-2025-08-27-1830","DOIUrl":"https://doi.org/10.22331/q-2025-08-27-1830","url":null,"abstract":"Quantum networks allow for novel forms of quantum nonlocality. By exploiting the combination of entangled states and entangled measurements, strong nonlocal correlations can be generated across the entire network. So far, all proofs of this effect are essentially restricted to the idealized case of pure entangled states and projective local measurements. Here we present noise-robust proofs of network quantum nonlocality, for a class of quantum distributions on the triangle network that are based on entangled states and entangled measurements. The key ingredient is a result of approximate rigidity for local distributions that satisfy the so-called “parity token counting'' property with high probability. Our methods can be applied to any type of noise. As illustrative examples, we consider quantum distributions obtained with imperfect sources and obtain a noise robustness up to $sim 80%$ for dephasing noise and up to $sim 0.5%$ for white noise. Additionally, we prove that all distributions in the vicinity of some ideal quantum distribution are nonlocal, with a bound on the total-variation distance $sim 0.25%$. Our work opens interesting perspectives towards the practical implementation of quantum network nonlocality.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"26 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905878","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

Classical certification of quantum gates under the dimension assumption 维度假设下量子门的经典认证

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-08 DOI: 10.22331/q-2025-08-08-1825

Jan Nöller, Nikolai Miklin, Martin Kliesch, Mariami Gachechiladze

{"title":"Classical certification of quantum gates under the dimension assumption","authors":"Jan Nöller, Nikolai Miklin, Martin Kliesch, Mariami Gachechiladze","doi":"10.22331/q-2025-08-08-1825","DOIUrl":"https://doi.org/10.22331/q-2025-08-08-1825","url":null,"abstract":"The rapid advancement of quantum hardware necessitates the development of reliable methods to certify its correct functioning. However, existing certification tests fall short, as they either suffer from systematic errors or do not guarantee that only a correctly functioning quantum device can pass the test. We introduce a certification method for quantum gates tailored for a practical server-user scenario, where a classical user tests the results of exact quantum computations performed by a quantum server. This method is free from the systematic state preparation and measurement (SPAM) errors. For single-qubit gates, including those that form a universal set for single-qubit quantum computation, we demonstrate that our approach offers soundness guarantees based solely on the dimension assumption. Additionally, for a highly-relevant phase gate – which corresponds experimentally to a $pi/2$-pulse – we prove that the method's sample complexity scales as $mathrm{O}(varepsilon^{-1})$ relative to the average gate infidelity $varepsilon$. By combining the SPAM-error-free and sound notion of certification with practical applicability, our approach paves the way for promising research into efficient and reliable certification methods for full-scale quantum computation.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"57 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144796913","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

Far from Perfect: Quantum Error Correction with (Hyperinvariant) Evenbly Codes 远非完美：（超不变）均匀码的量子纠错

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-08 DOI: 10.22331/q-2025-08-08-1826

Matthew Steinberg, Junyu Fan, Robert J. Harris, David Elkouss, Sebastian Feld, Alexander Jahn

{"title":"Far from Perfect: Quantum Error Correction with (Hyperinvariant) Evenbly Codes","authors":"Matthew Steinberg, Junyu Fan, Robert J. Harris, David Elkouss, Sebastian Feld, Alexander Jahn","doi":"10.22331/q-2025-08-08-1826","DOIUrl":"https://doi.org/10.22331/q-2025-08-08-1826","url":null,"abstract":"We introduce a new class of qubit codes that we call Evenbly codes, building on a previous proposal of hyperinvariant tensor networks. Its tensor network description consists of local, non-perfect tensors describing CSS codes interspersed with Hadamard gates, placed on a hyperbolic ${p,q}$ geometry with even $qgeq 4$, yielding an infinitely large class of subsystem codes. We construct an example for a ${5,4}$ manifold and describe strategies of logical gauge fixing that lead to different rates $k/n$ and distances $d$, which we calculate analytically, finding distances which range from $d=2$ to $d sim n^{2/3}$. Investigating threshold performance under erasure, depolarizing, and pure Pauli noise channels, we find that the code exhibits a depolarizing noise threshold of about 19.1% in the code-capacity model and 50% for pure Pauli and erasure channels under suitable gauges. We also test a constant-rate version with $k/n = 0.125$, finding excellent error resilience (about 40%) under the erasure channel. Recovery rates for these and other settings are studied both under an optimal decoder as well as a more efficient but non-optimal greedy decoder. We also consider generalizations beyond the CSS tensor construction, compute error rates and thresholds for other hyperbolic geometries, and discuss the relationship to holographic bulk/boundary dualities. Our work indicates that Evenbly codes may show promise for practical quantum computing applications.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"52 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144796888","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

Quantum control of continuous systems via nonharmonic potential modulation 基于非谐波电位调制的连续系统量子控制

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-08-08 DOI: 10.22331/q-2025-08-08-1824

Piotr T. Grochowski, Hannes Pichler, Cindy A. Regal, Oriol Romero-Isart

引用次数: 0