Investigation of measurement protected many-body quantum states

该奖项支持理论和计算研究和教育，以发现和研究由量子量子比特组成的受监控量子系统中的紧急现象。这些量子比特是经典比特的量子类似物，有两种截然不同的状态。它们是量子计算的基础。当量子比特耦合在一起时，就会产生量子纠缠，即使量子比特彼此分离得很远，量子纠缠也会将它们联系在一起。量子纠缠是量子力学的一种特殊性质，在这种情况下涉及多个量子比特，并为各种计算任务提供资源。在一个拥有多个量子比特的量子系统中，当它们耦合在一起时，整个系统可以在很长一段时间后成为高度纠缠的量子态。这种强烈的纠缠可以导致量子系统的热化并达到平静的平衡态。最近，人们发现，如果进一步对这些量子比特进行持续监测，系统可能会避免热化，并表现出有趣和异常的行为。PI和他的团队计划主要从量子纠缠的角度来研究受监控的多量子比特系统。在这些系统中，相互作用可以在量子比特之间建立量子纠缠，而测量可以通过向环境泄露信息来解开系统。它们之间的竞争可能会导致产生具有有趣的纠缠结构的新奇相。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，还将使用统计物理学的分析方法对这些新相进行分析和分类。这些研究活动有助于增进我们对多量子比特量子动力学的理解。这项研究是跨学科的，不仅可以对物理、材料研究产生重大影响，还可以对量子信息科学产生重大影响。PI的教育和外展活动与他的研究相结合。重点将放在指导对量子物理感兴趣的研究生和本科生上。这些学生将接受新一代研究人员的培训，以便他们能够在未来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项目和重点研讨会系列，以传达量子物理的重要性。TECHNICAL该奖项支持研究受监控量子系统中的量子相的理论和计算研究以及教育。与封闭的量子系统不同，封闭的量子系统通常在么正动力学下进行热化，而受到连续监测的量子系统受非么正动力学的支配，可以避免热化。最近，人们发现，通过调节监测强度，该系统可以经历从高度纠缠的体积律相到无纠缠的面积律相的连续量子相变。受这一发现的启发，本研究试图从量子纠缠的角度来探索非么正动力学中的非热相。我们将研究两类电路：(1)穿插重复测量的酉电路。这里的PI主要集中在重复测量的量子自动机(QA)电路上。该电路允许大规模的数值模拟，并为非么正动力学提供了良好的物理图像。通过引入各种对称性和约束，PI计划分析非么正QA电路中的各种非热体积定律相和临界相。PI还将开发一种有效的理论来理解和分类这些阶段。(2)受一层衡量的资源状态。这里，PI首先准备由浅电路生成的二维资源状态。通过监测整体自由度，一维边界态可以通过操控整体自由度而呈现出有趣的纠缠结构。PI将在先前随机电路研究的基础上，通过开发各种数值/分析工具来研究潜在的物理。此外，由于资源状态的准备只需要浅电路的事实，该协议可以潜在地在有噪声的近期设备中实现。教育活动的重点是指导对量子物理感兴趣的研究生/本科生。这些学生将接受新一代研究人员的培训，以便他们能够在未来跨学科和跨学科工作。PI还将为他所在大学的学生组织一个交流项目和重点研讨会系列，以传达量子物理的重要性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.