Stefano Mancini, Rodolfo Bonifacio
We address the timing problem in realizing correcting codes for quantum information processing. To deal with temporal uncertainties we employ a consistent quantum mechanical approach. The conditions for optimizing the effect of error correction in such a case are determined.
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Correcting for finite statistics effects in a quantum steering experiment
针对纠缠测试中有限统计导致假阳性的问题，提出一种利用半定规划的单边设备无关协议，无需层析成像即可校正表观信号效应，经实验验证违反概率显著优于现有方法，推动量子网络实用化。
Two possible applications of random decoupling are discussed. Whereas so far decoupling methods have been considered merely for quantum memories, here it is demonstrated that random decoupling is also a convenient tool for stabilizing quantum algorithms. Furthermore, a decoupling scheme is presented which involves a random decoupling method compatible with detected-jump error correcting quantum codes. With this combined error correcting strategy it is possible to stabilize quantum information against both spontaneous decay and static imperfections of a qubit-based quantum information processor…
A general error correction method is presented which is capable of correcting coherent errors originating from static residual inter-qubit couplings in a quantum computer. It is based on a randomization of static imperfections in a many-qubit system by the repeated application of Pauli operators which change the computational basis. This Pauli-Random-Error-Correction (PAREC)-method eliminates coherent errors produced by static imperfections and increases significantly the maximum time over which realistic quantum computations can be performed reliably. Furthermore, it does not require redundan…
Can robustness against experimental imperfections and noise be embedded into a quantum simulation? In this paper, we report on a special case in which this is possible. A spin chain can be engineered such that, in the absence of imperfections and noise, an unknown quantum state is transported from one end of the chain to the other, due only to the intrinsic dynamics of the system. We show that an encoding into a standard error correcting code (a Calderbank-Shor-Steane code) can be embedded into this simulation task such that a modified error correction procedure on read-out can recover from su…
Khovanov homology and quantum error-correcting codes
利用Khovanov同调及其扩展生成新的量子纠错码，并研究其在Reidemeister移动下的距离行为。
Quantum bits have technological imperfections. Additionally, the capacity of a component that can be implemented feasibly is limited. Therefore, distributed quantum computation is required to scale up quantum computers. This dissertation presents a new quantum computer architecture which takes into account imperfections, aimed to realize distributed computation by connecting quantum computers each of which consists of multiple quantum CPUs and memories. Quantum CPUs employ a quantum error correcting code which has faster logical gates and quantum memories employ a code which is superior in spa…
A random matrix theory approach is applied in order to analyze the localization properties of local spectral density for a generic system of coupled quantum states with strong static imperfection in the unperturbed energy levels. The system is excited by an external periodic field, the temporal profile of which is close to monochromatic one. The shape of local spectral density is shown to be well described by the contour obtained from a relevant model of periodically driven two-states system with irreversible losses to an external thermal bath. The shape width and the inverse participation rat…
The theory of stabilizer quantum error correction allows us to actively stabilize quantum states and simulate ideal quantum operations in a noisy environment. It is critical is to correctly diagnose noise from its syndrome and nullify it accordingly. However, hardware that performs quantum error correction itself is inevitably imperfect in practice. Here, we show that stabilizer codes possess a built-in capability of correcting errors not only on quantum information but also on faulty syndromes extracted by themselves. Shor's syndrome extraction for fault-tolerant quantum computation is natura…
High fidelity quantum information transport is necessary for most practical models of quantum computation. By analogy with optical wave guides, a spatio-temporally varying magnetic potential on a one dimensional spin chain can achieve high fidelity transport of spin excitations. By comparing different potential shapes, we establish the effects of potential shape on the fidelity and transport speed. We incorporate disorder into our model and show methods to minimise its effect on transport. Finally, we discuss implementations of our scheme in several accessible systems based on hydrogenic appro…
Surpassing the Global Heisenberg Limit Using a High-effciency Quantum Switch
本文提出超高效率量子开关，在考虑光子损耗和探测不完美等现实条件下，实验证明参数估计精度可真正超越全局海森堡极限，为量子计量优势开辟新路径。
Quantum information processing devices need to be robust and stable against external noise and internal imperfections to ensure correct operation. In a setting of measurement-based quantum computation, we explore how an intelligent agent endowed with a projective simulator can act as controller to adapt measurement directions to an external stray field of unknown magnitude in a fixed direction. We assess the agent's learning behavior in static and time-varying fields and explore composition strategies in the projective simulator to improve the agent's performance. We demonstrate the applicabil…
Optimization of Quantum Error Correcting Code under Temporal Variation of Qubit Quality
针对量子比特错误率随时间和空间波动导致固定码距量子纠错效率低下的问题，本文提出基于每日错误率自适应选择码距的方法，在 IBM 127 量子比特设备上实现物理量子比特开销降低 50%-71%，同时保持 80% 以上量子比特可用性。
The ability to protect quantum information from the effect of noise is one of the major goals of quantum information processing. In this article, we study limitations on the asymptotic stability of quantum information stored in passive N-qubit systems. We consider the effect of small imperfections in the implementation of the protecting Hamiltonian in the form of perturbations or weak coupling to a ground state environment. We prove that, regardless of the protecting Hamiltonian, there exists a perturbed evolution that necessitates a final error correcting step when the state of the memory is …
Making Trotterization adaptive and energy-self-correcting for NISQ devices and beyond
本文提出带守恒律反馈的自适应 Trotterization 量子算法，通过动态调整时间步长自校正误差、降低电路深度并实现受控长时间误差。
Approximate Dynamical Quantum Error-Correcting Codes
本文结合动力学码与近似量子纠错，利用策略码框架构造近似动力学码，并通过半定规划证明最优编码、解码和校验测量的唯一性与鲁棒性，同时提出时间 Petz 恢复映射。
AI-Enabled Decoding of Qubit Loss for Quantum Error-Correcting Codes
针对量子比特丢失破坏稳定子代数结构的问题，提出基于时空图神经网络（STGNN）的解码器，同时纠正标准泡利错误和定位丢失位置，逻辑精度优于传统算法，并能在十轮后识别90%以上丢失位置。
Lattice surgery protocols allow for the efficient implementation of universal gate sets with two-dimensional topological codes where qubits are constrained to interact with one another locally. In this work, we first introduce a decoder capable of correcting spacelike and timelike errors during lattice surgery protocols. Afterwards, we compute logical failure rates of a lattice surgery protocol for a biased circuit-level noise model. We then provide a new protocol for performing twist-free lattice surgery, where we avoid twist defects in the bulk of the lattice. Our twist-free protocol elimina…
Error-mitigated Geometric Quantum Control over an Oscillator
针对SNAP门受振荡器耦合诱导非线性限制的问题，提出结合泛函理论量子最优控制轨迹设计与几何相位的方案，可显著缓解两类误差并保持鲁棒性，为容错量子计算提供新途径。
Quantum State Compression with Polar Codes
针对 Schumacher 量子压缩电路复杂度高的问题，论文提出基于经典伴随式信源编码与 polar codes 的量子态压缩方案，并通过量子连续抵消解码完成仿真验证。
Quantum error correction is expected to be essential in large-scale quantum technologies. However, the substantial overhead of qubits it requires is thought to greatly limit its utility in smaller, near-term devices. Here we introduce a new family of special-purpose quantum error-correcting codes that offer an exponential reduction in overhead compared to the usual repetition code. They are tailored for a common and important source of decoherence in current experiments, whereby a register of qubits is subject to phase noise through coupling to a common fluctuator, such as a resonator or a spi…
Approximate k-uniform states: definition, construction and applications
本研究提出近似k-均匀态的概念，证明其可通过Haar随机系综和浅层随机量子电路高效构造，并建立其与近似量子纠错码的联系，为k-均匀态的实际应用奠定基础。
Strategic Code: A Unified Spatio-Temporal Framework for Quantum Error-Correction
本文提出统一时空量子纠错框架“战略码”，基于询问器和量子梳形式，涵盖动态与静态QECC，给出纠错条件并优化近似解，弥合动态QECC容错理论空白。
Correcting coherent quantum errors by going with the flow
通过被动误差校正策略，有效抑制相干误差累积，实现与泡利噪声模型相近的量子比特性能。
Interconnection of Quantum Networks at Urban scale: Analysis of Temporal Stability of Entangled Photon Sources
该研究针对城域量子网络互连需求，分析电信C波段纠缠光子源的时间稳定性，实验实现了城域部署下两源的可靠同步，为城市规模量子网络构建提供了实验支撑。
Mitigating Temporal Fragility in the XY Surface Code
针对XY表面码标准逻辑态制备测量中存在的脆弱时间边界问题，提出先将量子比特局域纠缠为GHZ类态再做稳定子测量的新协议，证明其故障构型数近乎二次减少，态制备码容量阈值达50%，实验条件下性能优于标准协议，且可反转用于测量。
Tailoring Bell inequalities to the qudit toric code and self testing
本文提出了一种针对$\mathbb{Z}_d$扭码的贝尔不等式构造方法，通过自测试验证三能级扭码子空间，为设备无关认证拓扑量子物质提供了新工具。
Floquet time-crystals as sensors of AC fields
本文研究离散时间晶体作为极弱交流场量子传感器的性能，利用量子Fisher信息度量证明其能突破散粒噪声极限并支持较长询问时间，且集体相互作用使其对协议不完美性具有鲁棒性。
Infinite Distance Extrapolation: How error mitigation can enhance quantum error correction
本文提出了一种结合量子误差缓解与量子误差校正的方法，通过将误差校正码的距离作为噪声参数，实现对量子计算中误差的有效抑制。
Error-resilient Reversal of Quantum Chaotic Dynamics Enabled by Scramblons
通过Scramblons理论，该研究在多体实验系统中首次提取了量子李雅普诺夫指数，实现了抗误差的量子混沌动力学反转。
Fault-tolerant compiling of classically hard IQP circuits on hypercubes
本文提出一种硬件高效的容错编译方法，通过将IQP线路与量子纠错码及中性原子阵列架构协同设计，在超立方体上实现了经典困难且可扩展的容错量子采样，并证明其具备指数级错误抑制能力。
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