Investigation of measurement protected many-body quantum states

测量保护多体量子态的研究

• 批准号: 2219735
• 负责人: Xiao Chen
• 金额: $ 31.51万
• 依托单位: Boston College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-15 至 2025-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2219735&HistoricalAwards=false
• 关键词: Investigation; measurement; protected; many; body

NONTECHNICALThis award supports theoretical and computational research and education to discover and study emergent phenomena in a monitored quantum system composed of quantum qubits. These qubits are quantum analogues of classical bits and have two distinct states. They are the fundamental blocks for quantum computing. When the qubits are coupled together, quantum entanglement is generated, which links the qubits together even when they are separated far away from each other. Quantum entanglement is a special property of quantum mechanics, in this case involving multiple qubits and provides the resource for various computational tasks. In a quantum system with many qubits, when they are coupled together, the entire system can become a highly entangled quantum state after a long time. This strong entanglement can lead to the quantum system thermalizing and reaching the tranquil state of equilibrium. Recently, it was discovered that if these qubits are further subject to continuous monitoring, the system may avoid thermalization and exhibit interesting and unusual behavior. The PI and his team plan to investigate monitored many-qubit systems, mainly from the perspective of quantum entanglement. In these systems, the interaction can build up quantum entanglement among the qubits while measurements can disentangle the system by leaking the information to the environment. The competition among them can potentially lead to the creation of novel phases with interesting entanglement structures. In this research, various quantum circuits and numerical tools will be developed to efficiently simulate quantum dynamics. In addition, analytical methods from statistical physics will be used to analyze and classify these new phases. These research activities can help advance our understanding of many-qubit quantum dynamics. The research is interdisciplinary in nature and can significantly impact not only physics, and materials research, but also quantum information science. The PI’s education and outreach activities are integrated with his research. The focus will be on mentoring graduate and undergraduate students interested in quantum physics. These students will be trained as a new generation of researchers, so that they will be able to work across and between disciplines in the future. The PI will also organize an exchange program and focused seminar series for the students in his home college to convey the importance of quantum physics. TECHNICALThis award supports theoretical and computational research and education to study quantum phases in a monitored quantum system. Different from a closed quantum system, which typically thermalizes under unitary dynamics, the quantum system subject to continuous monitoring is governed by non-unitary dynamics and may avoid thermalization. Recently, it was discovered that by tuning the monitoring strength, this system can undergo a continuous quantum phase transition from a highly entangled volume law phase to a disentangled area law phase. Motivated by this finding, this research intends to explore the non-thermal phases in non-unitary dynamics from the perspective of quantum entanglement. Two classes of circuits will be investigated: (1) Unitary circuits interspersed with repeated measurement. Here the PI mainly focuses on the quantum automaton (QA) circuit subject to repeated measurement. This circuit allows large scale numerical simulation and provides a nice physical picture for the non-unitary dynamics. By introducing various symmetries and constraints, the PI plans to analyze various non-thermal volume law phases and critical phases in the non-unitary QA circuit. The PI will also develop an effective theory to understand and classify these phases. (2) Resource state subject to one layer of measurement. Here the PI first prepares a two-dimensional resource state generated by a shallow circuit. By monitoring the bulk degrees of freedom, the one-dimensional boundary state can exhibit interesting entanglement structure by manipulating the bulk degrees of freedom. The PI will study the underlying physics by developing various numerical/analytical tools based on the previous study of random circuits. In addition, this protocol can be potentially realized in the noisy near-term devices due to the fact that the preparation of the resource state only requires a shallow circuit. The educational activity focuses on mentoring graduate/undergraduate students interested in quantum physics. These students will be trained as a new generation of researchers, so that they will be able to work across and between disciplines in the future. The PI will also organize an exchange program and focused seminar series for the students in his home college to convey the importance of quantum physics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术性该奖项支持理论和计算研究和教育，以发现和研究由量子位组成的受监控量子系统中的新兴现象。这些量子位是经典位的量子类似物，并且具有两种不同的状态，它们是量子计算的基本块。量子位耦合在一起，产生量子纠缠，即使量子位彼此相距很远，量子纠缠也能将它们连接在一起。在这种情况下，量子纠缠是量子力学的一个特殊性质。在具有多个量子位的量子系统中，当它们耦合在一起时，经过很长一段时间，整个系统会变成高度纠缠的量子态，这种强纠缠会导致量子系统热化。最近，人们发现，如果这些量子位进一步受到连续监控，系统可能会避免热化并表现出有趣且不寻常的行为，PI 和他的团队计划研究受监控的多量子位。主要从量子纠缠的角度来看，在这些系统中，量子位之间的相互作用可以建立量子纠缠，而测量可以通过向环境泄漏信息来解开系统，它们之间的竞争可能会导致新奇事物的产生。在这项研究中，将开发各种量子电路和数值工具来有效地模拟量子动力学。此外，统计物理学的分析方法将用于分析和分类这些新的相。我们的理解该研究本质上是跨学科的，不仅可以对物理学和材料研究产生重大影响，而且还可以将量子信息科学与他的研究相结合。对量子物理感兴趣的本科生将被培养成为新一代的研究人员，以便他们将来能够跨学科工作，PI还将为学生组织交流项目和系列研讨会。在他家乡的大学里传达量子的重要性技术该奖项支持理论和计算研究和教育，以研究受监控量子系统中的量子相，与通常在单一动力学下热化的封闭量子系统不同，受到连续监控的量子系统受非单一动力学和控制。最近，人们发现，通过调整监测强度，该系统可以经历从高度纠缠体积定律相到解纠缠面积定律相的连续量子相变。受这一发现的启发，本研究打算探索这一现象。从量子纠缠的角度研究非酉动力学中的非热相。将研究两类电路：（1）散布重复测量的酉电路这里PI主要关注重复测量的量子自动机（QA）电路。该电路允许大规模数值模拟，并为非酉动力学提供良好的物理图像。通过引入各种对称性和约束，PI 计划分析非酉中的各种非热体积定律相和临界相。 QA 电路还将开发一种有效的理论来理解和分类这些阶段（2）受一层测量影响的资源状态，PI 首先通过监控浅层电路来准备二维资源状态。体自由度，一维边界态可以通过操纵体自由度表现出有趣的纠缠结构。此外，PI 将通过开发各种数值/分析工具来研究基础物理。该协议有可能实现由于资源状态的准备只需要浅层电路，因此近期设备的噪音很大。教育活动的重点是指导对量子物理学感兴趣的研究生/本科生，这些学生将被培训为新一代的研究人员。以便他们将来能够跨学科和跨学科工作。PI 还将为他所在大学的学生组织交流计划和重点研讨会系列，以传达量子物理学的重要性。该奖项反映了 NSF 的法定使命和使命。通过评估被认为值得支持基金会的智力价值和更广泛的影响审查标准。

项目成果

Entanglement dynamics in U(1) symmetric hybrid quantum automaton circuits

U(1) 对称混合量子自动机电路中的纠缠动力学

• DOI: 10.22331/q-2023-12-06-1200
• 发表时间: 2023-12
• 期刊: Quantum
• 影响因子: 6.4
• 作者: Han, Yiqiu;Chen, Xiao
• 通讯作者: Chen, Xiao

Robust Oscillations and Edge Modes in Nonunitary Floquet Systems

非酉 Floquet 系统中的鲁棒振荡和边缘模式

• DOI: 10.1103/physrevlett.130.230402
• 发表时间: 2023-06
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: Ravindranath, Vikram;Chen, Xiao
• 通讯作者: Chen, Xiao

Entanglement steering in adaptive circuits with feedback

带反馈的自适应电路中的纠缠转向

• DOI: 10.1103/physrevb.108.l041103
• 发表时间: 2023-07
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Ravindranath, Vikram;Han, Yiqiu;Yang, Zhi;Chen, Xiao
• 通讯作者: Chen, Xiao