Quantum non-demolition measurements: Concepts, theory and practice

Residual and Destroyed Accessible Information after Measurements

When quantum states are used to send classical information, the receiver performs a measurement on the signal states. The amount of information extracted is often not optimal due to the receiver's measurement scheme and experimental apparatus. For quantum non-demolition measurements, there is potentially some residual information in the post-measurement state, while part of the information has been extracted and the rest is destroyed. Here, we propose a framework to characterize a quantum measurement by how much information it extracts and destroys, and how much information it leaves in the re…

研究生量子力学中基于刻意练习理念的补充干预评估

Evaluation of a deliberate-practice informed supplemental intervention in graduate Quantum Mechanics

本研究为研究生量子力学课程设计了一项基于刻意练习理念的补充干预措施，以支持学生在有限信息下进行决策，结果显示干预后学生问题解决技能未见统计学显著改善，但概念理解有所提升。

Towards a heralded eigenstate preserving measurement of multi-qubit parity in circuit QED

Eigenstate-preserving multi-qubit parity measurements lie at the heart of stabilizer quantum error correction, which is a promising approach to mitigate the problem of decoherence in quantum computers. In this work we explore a high-fidelity, eigenstate-preserving parity readout for superconducting qubits dispersively coupled to a microwave resonator, where the parity bit is encoded in the amplitude of a coherent state of the resonator. Detecting photons emitted by the resonator via a current biased Josephson junction yields information about the parity bit. We analyse theoretically the measur…

Assessing the quantumness of the annealing dynamics via Leggett Gargs inequalities: a weak measurement approach

Adiabatic quantum computation (AQC) is a promising counterpart of universal quantum computation, based on the key concept of quantum annealing (QA). QA is claimed to be at the basis of commercial quantum computers and benefits from the fact that the detrimental role of decoherence and dephasing seems to have poor impact on the annealing towards the ground state. While many papers show interesting optimization results with a sizable number of qubits, a clear evidence of a full quantum coherent behavior during the whole annealing procedure is still lacking. In this paper we show that quantum non…

Quantum Radars and Lidars: Concepts, realizations, and perspectives

In this article, we review the basic concepts of quantum radars as such types of the devices while highlighting differences with their classical analogs. We discuss how several concepts from traditional radars technology, e.g., target detection sensitivity, noise resilience and ranging accuracy can be translated to quantum radars. We examine such new far-field sensing protocols as quantum illumination (QI), and engineering opportunities enabled by its different realizations. We consider possibilities of achieving super-sensitivity and super-resolution using quantum correlations, and discuss po…

量子扩散、测量与滤波

Quantum Diffusion, Measurement and Filtering

简要介绍了量子概率论中的基本概念，并与经典概率论进行了比较。量子白噪声的概念，它在Fock空间中的显式表示，以及非交换随机分析和集成的必要结果进行了概述。导出了量子非马尔可夫扩散与连续非破坏观测统一的代数微分方程。将经典的马尔可夫滤波方程推广到任意 *-代数上的量子流，得到了量子扩散滤波的随机方程。考虑一维连续观测的高斯量子扩散，将后验量子态扩散化为线性Kalman-Bucy型量子随机滤波方程和量子关联的Riccati算子方程.考虑了一个自由量子粒子坐标连续非破坏观测的例子，描述了线性量子滤波问题的定态解的一种连续的碰撞.

A new type of quantum speed meter interferometer: measuring speed to search for intermediate mass black holes

The recent discovery of gravitational waves (GW) by LIGO has impressively launched the novel field of gravitational astronomy and it allowed us to glimpse at exciting objects we could so far only speculate about. Further sensitivity improvements at the low frequency end of the detection band of future GW observatories rely on quantum non-demolition (QND) methods to suppress fundamental quantum fluctuations of the light fields used to readout the GW signal. Here we invent a novel concept of how to turn a conventional Michelson interferometer into a QND speed meter interferometer with coherently…

采用数字零噪声外推法进行量子误差缓解的最佳实践

Best practices for quantum error mitigation with digital zero-noise extrapolation

本文针对数字零噪声外推法（dZNE）应用于量子误差缓解时的实操难点，结合文献与实验总结出覆盖全工作流步骤的最佳实践，为该方法推广及提升含噪声量子硬件计算的可复现性与严谨性提供支撑。

量子计算概念库存的益处与挑战

The Benefits and Challenges of a Quantum Computing Concept Inventory

本文探讨了构建量子计算概念库存的必要性与挑战，通过专家访谈确定关键概念，并强调了国际协作与教育适应性的重要性。