Controlling Nonclassical Atomic Spin Ensembles via Cavity-Enhanced Polarization Measurements

量子信息科学(QIS)是一个新兴领域，将推动下一次数字信息革命。它基于一种革命性的想法，即当信息在原子和光子的微观水平上被操纵时，奇怪的物理定律使超高速计算机、增强的网络安全和超精密传感器成为可能。加快QIS的进展是2018年国家量子倡议法案的目标，以加强国家安全和经济增长。这笔赠款通过开发一种新的原子-光子界面来帮助实现这些目标，该界面在量子计算、通信和传感方面具有潜在的应用。它通过理论原子物理的基础研究来做到这一点，这对发展下一代信息处理技术至关重要。该项目涉及培训学生，他们将创造新的量子智能劳动力。这个项目的目标是开发一个新的纠缠原子光界面平台，可以用来创建原子自旋系综的非经典态，用于计量学、量子通信、量子计算和复杂多体动力学的基础研究。该平台基于环形腔几何结构，能够在铯原子的磁敏钟态中编码的原子自旋与光的偏振之间实现强烈的双折射色散相互作用。在腔输出端口处测量光的偏振度会引起集体原子自旋的量子反向作用。该项目将探索光的高斯(零差)测量来诱导原子的高斯纠缠态(自旋压缩)，非高斯(光子计数)测量来诱导非高斯原子自旋态(Dicke态)，以及类似于压缩真空态上的光子加成的混合方法。该小组将在详细了解连续测量量子轨迹的基础上，开发新的量子态验证和断层扫描方法。此外，该小组将开发一种新的基于测量的反馈方法，以创建集体自旋的复杂动力学图，并能够研究量子混沌、量子到经典的转变以及多体物理的量子模拟。这一奖项反映了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。

Quantum Information Science (QIS) is an emerging field that will fuel the next digital information revolution. It is based on the revolutionary idea that when information is manipulated at the microscopic level of atoms and photons the strange laws of physics enable ultrafast computers, enhanced cyber security, and ultraprecise sensors. Accelerating progress in QIS is the goal of the National Quantum Initiative Act of 2018, to enhance the nation’s security and economic growth. This grant helps to achieve these goals by developing a new atom-photon interface with potential applications in quantum computing, communications, and sensing. It does so through basic research in theoretical atomic physics which is essential for the development of next-generation information processing technologies. The project involves the training of students who will create the new quantum-smart workforce. The goal of this project is to develop a new platform for an entangling atom-light interface that can be used to create nonclassical states of atomic spin ensembles for applications in metrology, quantum communication, quantum computation, and fundamental studies of complex many-body dynamics. This platform is based on a ring-cavity geometry that enables a strong birefringent dispersive interaction between atomic spins encoded in magnetically insensitive clock states of cesium atoms and the polarization of the light. Measurement of the light polarization at the cavity output port induces quantum backaction of the collective atomic spin. The project will explore both Gaussian (homodyne) measurements of the light to induce Gaussian entangled states of atoms (spin squeezing), nonGaussian (photon counting) measurements to induce nonGaussian atomic spin states (Dicke states), as well as hybrid approaches analogous to photon addition on a squeezed vacuum state. The group will develop new approaches to quantum state verification and tomography based on detailed understanding of continuous measurement quantum trajectories. Additionally, the group will develop a new approach to measurement-based feedback to create complex dynamical maps of the collective spins and enable studies of quantum chaos, the quantum-to-classical transition, and quantum simulation of many-body 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.