通过跟踪控制稳定量子位相干性

Tracking quantum coherence in polariton condensates with time-resolved tomography

Long-term quantum coherence constitutes one of the main challenges when engineering quantum devices. However, easily accessible means to quantify complex decoherence mechanisms are not readily available, nor are sufficiently stable systems. We harness novel phase-space methods - expressed through non-Gaussian convolutions of highly singular Glauber-Sudarshan quasiprobabilities - to dynamically monitor quantum coherence in polariton condensates with significantly enhanced coherence times. Via intensity- and time-resolved reconstructions of such phase-space functions from homodyne detection data…

具有零差测量的随机量子动力学的状态估计与控制：不确定性下的量子比特镇定

State Estimation and Control for Stochastic Quantum Dynamics with Homodyne Measurement: Stabilizing Qubits under Uncertainty

本文针对零差测量下具有不确定性的随机量子系统，提出基于李雅普诺夫切换控制的量子比特镇定方法，并通过多模型估计与状态重建保证概率意义下的实际稳定。

Stabilizing Rabi Oscillation of a Charge Qubit via Atomic Clock Technique

We propose a superconducting circuit-atom hybrid, where the Rabi oscillation of single excess Cooper pair in the island is stabilized via the common atomic-clock technique. The noise in the superconducting circuit is mapped onto the voltage source which biases the Cooper-pair box via an inductor and a gate capacitor. The fast fluctuations of the gate charge are significantly suppressed by an inductor-capacitor resonator, leading to a long-relaxation-time Rabi oscillation. More importantly, the residual low-frequency fluctuations are further reduced by using the general feedback-control method,…

仅利用驱动和耗散将相干时间延长至盈亏平衡点以上

Extending coherence time beyond break-even point using only drives and dissipation

本文提出一种基于量子信道模拟的自主量子纠错协议，适用于任意纠错码，并在玻色子模式中实验实现，将逻辑量子比特相干时间延长至最佳物理量子比特的1.04倍，首次超越盈亏平衡点，证明仅用驱动和耗散即可延长相干时间。

Tracking Attosecond Electronic Coherences Using Phase-Manipulated Extreme Ultraviolet Pulses

The recent development of ultrafast extreme ultraviolet (XUV) coherent light sources bears great potential for a better understanding of the structure and dynamics of matter. Promising routes are advanced coherent control and nonlinear spectroscopy schemes in the XUV energy range, yielding unprecedented spatial and temporal resolution. However, their implementation has been hampered by the experimental challenge of generating XUV pulse sequences with precisely controlled timing and phase properties. In particular, direct control and manipulation of the phase of individual pulses within a XUV p…

超越十小时的相干性在去相干自由的囚禁离子钟量子比特中

Beyond-Ten-Hour Coherence in a Decoherence-Free Trapped-Ion Clock Qubit

本文通过结合钟态量子比特与去相干自由子空间编码，实现了超过十小时的相干性，突破了传统技术限制，为可扩展的量子信息处理奠定了基础。

量子门的群论与量子相干性

On group theory for quantum gates and quantum coherence

有限群扩张为量子计算提供了一种自然语言。简而言之，量子计算机的作用大致由两组有限的门组成：来自一般泡利群P的错误门和扩展群C内的稳定门。在本文中，人们探讨了良好的充分性之间的组理论概念，如recruitors，正常的子群，组的自同构，短的确切序列，圈产品...和相干量子计算基元。详细分析了单量子比特和双量子比特Clifford群的结构。作为副产品，人们发现M20是最小的完美群，换位子群从交换子集合中分离出来，它是两量子比特系统的量子相干性的基础。一个恢复类似的结果，通过寻找一个完整的一组相互无偏基地的自同构。

Switching Quantum Dynamics for Fast Stabilization

Control strategies for dissipative preparation of target quantum states, both pure and mixed, and subspaces are obtained by switching between a set of available semigroup generators. We show that the class of problems of interest can be recast, from a control--theoretic perspective, into a switched-stabilization problem for linear dynamics. This is attained by a suitable affine transformation of the coherence-vector representation. In particular, we propose and compare stabilizing time-based and state-based switching rules for entangled state preparation, showing that the latter not only ensur…

Scalable Digital Hardware for a Trapped Ion Quantum Computer

Many of the challenges of scaling quantum computer hardware lie at the interface between the qubits and the classical control signals used to manipulate them. Modular ion trap quantum computer architectures address scalability by constructing individual quantum processors interconnected via a network of quantum communication channels. Successful operation of such quantum hardware requires a fully programmable classical control system capable of frequency stabilizing the continuous wave lasers necessary for trapping and cooling the ion qubits, stabilizing the optical frequency combs used to dri…

通过二分搜索哈密顿量跟踪实现高效量子比特校准

Efficient Qubit Calibration by Binary-Search Hamiltonian Tracking

本文提出一种基于二分搜索的实时量子比特频率校准协议，通过动态生成探测序列实现指数级精度提升，并在transmon量子比特上验证了其改善相干性和门保真度，且能部分缓解非马尔可夫噪声。

磁场下各向异性 $XY$ 两量子比特中的量子关联与相干性

Quantum correlations and coherence in a two-qubit anisotropic $XY$ under magnetic field

研究均匀磁场下各向异性 Heisenberg $XY$ 模型的热量子关联与相干性，分析磁各向异性、耦合各向异性、DM 相互作用、温度和磁场对量子资源的调控，发现非定域性最先消失，相干性最鲁棒。