G. M. D'Ariano, S. Facchini, P. Perinotti, M. F. Sacchi
We present probability-fidelity tradeoffs for a varying quantum operation with fixed input-output states and for a varying inversion of a fixed quantum operation.
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We propose a method of optimally controlling state transfer through a noisy quantum channel (spin-chain). This process is treated as qubit state-transfer through a fermionic bath. We show that dynamical modulation of the boundary-qubits levels suffices to ensure fast and high-fidelity state transfer. This is achievable by dynamically optimizing the transmission spectrum of the channel. The resulting optimal control is robust against both static and fluctuating noise.
We show that the global balance of information dynamics for general quantum measurements given in [F. Buscemi, M. Hayashi, and M. Horodecki, Phys.Rev.Lett. 100, 210504 (2008)] makes it possible to unify various and generally inequivalent approaches adopted in order to derive information-disturbance tradeoffs in quantum theory. We focus in particular on those tradeoffs, constituting the vast majority of the literature on the subject, where disturbance is defined either in terms of average output fidelity or of entanglement fidelity.
We present the amounts of information, fidelity, and reversibility obtained by arbitrary quantum measurements on completely unknown states. These quantities are expressed as functions of the singular values of a measurement operator corresponding to the obtained outcome. As an example, we consider a class of quantum measurements with highly degenerate singular values to discuss tradeoffs among information, fidelity, and reversibility. The tradeoffs are at the level of a single outcome, in the sense that the quantities pertain to each single outcome rather than the average over all possible out…
Using PT-symmetric Qubits to Break the Tradeoff Between Fidelity and the Degree of Quantum Entanglement
本文提出利用具有平衡增益和损耗的有源PT对称系统，在奇异点附近快速制备高保真度、高纠缠度的多量子比特纠缠态，从而打破纠缠度与保真度之间的固有权衡。
We show the flaws found in the customary fidelity-based definitions of disturbance in quantum measurements and evolutions. We introduce the "entropic disturbance" D and show that it adequately measures the degree of disturbance, intended essentially as an irreversible change in the state of the system. We also find that it complies with an information-disturbance tradeoff, namely the mutual information between the eigenvalues of the initial state and the measurement results is less than or equal to D.
Rate-Fidelity Tradeoffs in All-Photonic and Memory-Equipped Quantum Switches
本文研究了全光子和配备量子记忆的量子交换机在速率与保真度之间的权衡，通过比较两种架构的性能，提出了评估方法并分析了其在不同应用场景中的优化策略。
ReFINE: Scheduling of Distillation and Coding for Rate-Fidelity Tradeoff in Quantum Networks
ReFINE是一种需求感知的抢占式调度器，通过动态调度纠缠蒸馏与编码增强内存的形成，在量子网络中实现速率与保真度的最优权衡。
Exact Tradeoff Between Quantum Error Correction and Quantum Darwinism: An Information-Theoretic No-Go Theorem
该研究建立了量子纠错与量子达尔文主义间的精确权衡关系，证明逻辑保真度超临界阈值会阻碍达尔文主义冗余度出现，首次给出二者的定量信息论联系。
We demonstrate a fundamental principle of disturbance tradeoff for quantum measurements, along the lines of the celebrated uncertainty principle: The disturbances associated with measurements performed on distinct yet identically prepared ensembles of systems in a pure state cannot all be made arbitrarily small. Indeed, we show that the average of the disturbances associated with a set of projective measurements is strictly greater than zero whenever the associated observables do not have a common eigenvector. For such measurements, we show an equivalence between disturbance tradeoff measured …
Although the quality of quantum bits (qubits) and quantum gates has been steadily improving, the available quantity of qubits has increased quite slowly. To address this important issue in quantum computing, we have demonstrated arbitrary single qubit gates based on targeted phase shifts, an approach that can be applied to atom, ion or other atom-like systems. These gates are highly insensitive to addressing beam imperfections and have little crosstalk, allowing for a dramatic scaling up of qubit number. We have performed gates in series on 48 individually targeted sites in a 40% full $5\times…
Design Tradeoffs in Photonically Linked Qubit Networks
本文研究基于囚禁离子与小型光学腔强耦合的两种量子纠缠分发协议，在相同实验约束下与传统双光子干涉方案比较，发现可在保持99%以上保真度的同时将分发速率提升30-75%。
Local Gaussian bounds on the non-destructive discrimination of two-mode squeezed states
本研究探究利用局域高斯测量对双模压缩态的非破坏性区分，构造最优协议并扩展至含预共享纠缠的情形，将信息增益与扰动的权衡从有限维系统拓展至连续变量系统。
We propose a method of optimally controlling the tradeoff of speed and fidelity of state transfer through a noisy quantum channel (spin-chain). This process is treated as qubit state-transfer through a fermionic bath. We show that dynamical modulation of the boundary-qubits levels can ensure state transfer with the best tradeoff of speed and fidelity. This is achievable by dynamically optimizing the transmission spectrum of the channel. The resulting optimal control is robust against both static and fluctuating noise in the channel's spin-spin couplings. It may also facilitate transfer in the …
An arbitrary qubit can be transmitted through a spin chain by perturbatively coupling both communicating parties to it. Those so-called weak-coupling models rely on effective Rabi oscillations between them, yielding nearly maximum fidelity while offering great resilience against disorder with the cost of having long transfer times. Considering this framework, here we address a 1D non-symmetric channel connecting two spins, one placed at each end of it. Given any pattern of nearest-neighbor coupling strengths, we obtain an analytical expression that accounts for the effective long-range interac…
Measurement sharpness and disturbance tradeoff
本文研究了量子测量中信息获取与状态扰动之间的权衡问题，提出了多种方法解决无偏二元量子比特测量中的最小扰动和最佳信息获取问题，并揭示了测量锐度与平均保真度、量子资源之间的权衡关系。
Tradeoff between noise and banding in a quantum adder with qudits
本文研究任意维度量子加法器的资源需求，证明受控旋转门数量上界，并揭示噪声下带状限制使恒定深度近似电路更优，同时提出用一维自旋链实现量子加法的方案。
The production of conditional quantum states and quantum operations based on the result of measurement is now seen as a key tool in quantum information and metrology. We propose a new type of photon number detector. It functions non-deterministically, but when successful, it has high fidelity. The detector, which makes use of an n-photon auxiliary Fock state and high efficiency Homodyne detection, allows a tunable tradeoff between fidelity and probability. By sacrificing probability of operation, an excellent approximation to a photon number detector is achieved.
High-purity entanglement mediated by magnons despite weak coupling
研究远距离自旋纠缠面临的耦合权衡问题，提出通过磁振子与计算基外跃迁耦合的协议打破权衡，分析了自旋为两个氮空位中心的设置，模拟得出不同速率下的保真度和成功概率。
The realization of high fidelity quantum gates in a multi-qubit system, with a typical target set at 99.9%, is a critical requirement for the implementation of fault-tolerant quantum computation. To reach this level of fidelity, one needs to carefully analyze the noises and imperfections in the experimental system and optimize the gate operations to mitigate their effects. Here, we consider one of the leading experimental systems for the fault-tolerant quantum computation, ions in an anharmonic linear Paul trap, and optimize entangling quantum gates using segmented laser pulses with the assist…
QOS: A Quantum Operating System
针对量子计算机资源管理的挑战，提出云量子操作系统QOS，通过硬件无关API、错误缓解及跨时空调度作业，在IBM设备上实现保真度提升、利用率提高和等待时间缩短，平衡量子计算性能权衡。
Quantum measurement is important to quantum computing as it extracts the outcome of the circuit at the end of the computation. Previously, all measurements have to be done at the end of the circuit. Otherwise, it will incur significant errors. But it is not the case now. Recently IBM started supporting dynamic circuits through hardware (instead of software by simulator). With mid-circuit hardware measurement, we can improve circuit efficacy and fidelity from three aspects: (a) reduced qubit usage, (b) reduced swap insertion, and (c) improved fidelity. We demonstrate this using real-world appli…
Consecutive Measurement Tradeoffs in Quantum Cryptography
本文研究了量子密码学中连续测量对信息提取的影响，提出连续测量定理框架，改进了成功概率的界限，并为多种密码原语提供了更强的安全保证。
End-to-End Fidelity and Rate Analysis for Zero-Added-Loss Multiplexing
本文针对基于光谱岛的零附加损耗复用（ZALM）开展端到端保真度与速率分析，涵盖多类损耗，以解决传统方案的效率-保真度权衡问题。
A Nonstabilizerness Resource Law for Universal Quantum State Purification
研究通用量子态纯化，通过证明奇数维线性魔力定律和多量子比特系统双边线性鲁棒性定律，确定成功纯化映射，建立通用纯化的定量魔法 - 保真度定律，将魔法资源与容错量子信息处理相联系。
Fidelity-Aware Frequency Allocation and Transpilation Co-Design for Tunable Coupler Quantum Systems
本文提出了一种考虑保真度的可调耦合量子系统频率分配与转译联合设计框架，通过误差预算方法建模相干观察者诱导误差和非相干寿命效应，分析频率拥挤对门保真度的影响，并提出约束优化问题来分配量子比特和耦合器频率，同时展示可扩展的频率分配策略以减少观察者诱导误差，并展示在模块内增加量子比特数量和耦合密度会导致保真度与连接性之间的权衡。
Crosstalk-Resilient Quantum MIMO for Scalable Quantum Communications
针对量子复用中的串扰问题，提出基于 GKP 码将离散变量量子信息编码至连续变量模式的缓解策略，证明了特定条件下相互作用可被规范子系统吸收以保持逻辑内容，为量子网络抗串扰复用奠定理论基础。
Quantum Reinforcement Learning for Cost and Delay Tradeoffs in Quantum Cloud Orchestration
提出QRLQ框架，将参数化量子电路与决斗双深度Q网络结合，在量子云编排中实现成本与延迟权衡，相比启发式方法降低成本延迟，且参数更少。
Effective quantum volume, fidelity and computational cost of noisy quantum processing experiments
本文提出基于有效线路体积的统一框架，解释含噪量子实验中可观测量信噪比与经典计算成本的权衡，并在随机线路采样、量子信息置乱和Floquet实验上验证，实现单GPU每点不到一秒复现结果。
We study the problem of quantum hacking, which is the procedure of quantum-information extraction from and installation on a quantum network given only partial access. This problem generalizes a central topic in contemporary physics -- information recovery from systems undergoing scrambling dynamics, such as the Hayden--Preskill protocol in black-hole studies. We show that a properly prepared partially entangled probe state can generally outperform a maximally entangled one in quantum hacking. Moreover, we prove that finding an optimal decoder for this stronger task is equivalent to that for H…
Qubit measurements are central to quantum information processing. In the field of superconducting qubits, standard readout techniques are not only limited by the signal-to-noise ratio, but also by state relaxation during the measurement. In this work, we demonstrate that the limitation due to relaxation can be suppressed by using the many-level Hilbert space of superconducting circuits: in a multilevel encoding, the measurement is only corrupted when multiple errors occur. Employing this technique, we show that we can directly resolve transmon gate errors at the level of one part in $10^3.$ Ex…
Rate-Fidelity Control for Wide-Area Quantum Links
该研究针对广域光纤量子链路的偏振漂移问题，构建联合控制协议动态调整参数，在保真度约束下提升纠缠分发速率，模拟显示其较静态策略提升14%且无需离线优化。
Robust quantum computation with d-level quantum systems (qudits) poses two requirements: fast, parallel quantum gates and high fidelity two-qudit gates. We first describe how to implement parallel single qudit operations. It is by now well known that any single-qudit unitary can be decomposed into a sequence of Givens rotations on two-dimensional subspaces of the qudit state space. Using a coupling graph to represent physically allowed couplings between pairs of qudit states, we then show that the logical depth of the parallel gate sequence is equal to the height of an associated tree. The imp…
Tradeoffs between the information rate and fidelity of quantum error-correcting codes are discussed. Quantum channels to be considered are those subject to independent errors and modeled as tensor products of copies of a general completely positive linear map, where the dimension of the underlying Hilbert space is a prime number. On such a quantum channel, the highest fidelity of a quantum error-correcting code of length $n$ and rate R is proven to be lower bounded by 1 - \exp [-n E(R) + o(n)] for some function E(R). The E(R) is positive below some threshold R', which implies R' is a lower bou…
InterQ: Communication-Aware Scheduling Across Modular QPUs with Classical and Quantum Links
本文提出InterQ，一种用于具有异构通信模型的模块化QPUs的通信感知调度器，通过考虑量子比特容量、放置、并行执行和跨分布式子电路的通信驱动依赖性，减少makespan并平衡保真度和通信开销，展示了不同通信模型和调度器驱动的切割决策对吞吐量、延迟和保真度的影响。
Privacy-Utility Tradeoffs in Quantum Information Processing
本文研究了量子信息处理中隐私与效用的权衡，提出通过去极化机制优化隐私-效用平衡，并展示了私有学习可观测量期望值所需的样本数与隐私和准确性参数的关系。
Robust control of quantum gates via sequential convex programming
本文提出基于序列凸规划的方法，在控制幅度和带宽资源受限的情况下，使量子门变换对不确定性具有高度鲁棒性，并探索了最坏情况门保真度与场通量之间的权衡。
Estimating the Effect of Crosstalk Error on Circuit Fidelity Using Noisy Intermediate-Scale Quantum Devices
本研究提出一种结合随机基准测试与同时随机基准测试的简单实用方法，用于估计NISQ器件上的串扰误差，并在IBM多量子比特器件上验证，通过插入指令屏障将电路保真度提升至多3.06倍。
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