Condensed Matter Theory

该奖项支持理论凝聚态物理学、量子光学和使用电路和腔QED的量子信息处理的研究和教育。该研究建立在上一个资助期的理论进展基础上，并受到最近在电路量子力学和通过辐射压力操纵纳米机械系统方面的巨大实验和理论进展的推动。受“电路QED”最近实验进展的推动，PI将继续与耶鲁大学Schoelkopf和Devoret实验组进行富有成效的合作，以实现微波电路中的新型和基本强耦合量子光学。PI将开发超导量子比特和谐振器晶格中强相互作用微波极化激元的多体物理理论模型。这种晶格可以用来模拟强关联的玻色子以及受抑的量子自旋。轴子是理论上提出存在的基本粒子，是解释宇宙中弥漫的冷暗物质的重要候选者。在强磁场的存在下，它们预计会衰变成微波光子。电路QED的进展正在接近一个点，他们可以大大改变轴子暗物质搜索的方式。根据最新的实验进展，PI将评估不同可能的方法来优化轴子搜索中的微波光子探测的有效性。PI还将继续与耶鲁大学实验组的Jack Harris和Hong Tang在光纳米力学方面的合作，并开始与新教员Peter Rakich的合作。哈里斯的一个新方向将是发展可变形的液氦悬浮液滴的回音壁模式的光力学模型。另一个将是与Rakich合作，研究在片上光机械布里渊激光器中可以实现的窄线宽的理论和实践极限。将发展量子光学思想在超导电路和光机械系统中的应用和扩展。一个新的方向将是提出和发展量子浴工程的新想法，这将创造“摩擦”，目的是自然地放松量子系统，而不是朝着它们的基态，而是朝着预定的纠缠多体状态感兴趣。这些想法可能会广泛适用于超导量子比特之外的原子物理系统和其他类型的量子比特以及量子模拟。这项工作具有很强的跨学科组成部分，汇集了凝聚态，原子物理学和量子光学社区中使用的思想和方法。PI与实验组的密切合作正在导致单光子水平上的新的精密微波测量技术，该技术将在量子信息处理之外应用于探测纳米级系统，并产生了新的超低-噪声微波放大器和探测器。非技术性总结该奖项支持理论研究和教育的人造原子从电路由材料制成是超导体。超导体表现出一种量子力学状态，它可以导电而不耗散。像真实的原子一样，这些人造原子可以与微波辐射的单个量子或光子相互作用。这些超导电路正在被开发为构建量子计算机的基本硬件。量子计算机将通过操纵量子力学状态来执行计算，原则上可以在某些问题上大大超过现有最快的计算机。除了这种潜在的实际应用之外，这些超导电路还可以用于有效地检测单个微波光子。 研究员将探索这项新能力在改进轴子探测方面的应用，轴子是解决宇宙学和天体物理学中“暗物质”问题的基本粒子。研究员还将继续研究光力学理论，即光施加的微弱压力可以用来引起小物体的机械运动，甚至冷却它们的运动。这是一项全新的技术，在光通信和测量中具有实际应用。 特别重要的是与实验同事一起探索新的想法，应用光的辐射压力来移动和扭曲超流氦的磁悬浮液滴。

TECHNICAL SUMMARYThis award supports research and education in theoretical condensed matter physics, quantum optics, and quantum information processing using circuit and cavity QED. The research builds upon theoretical progress during the previous grant period and is driven by recent dramatic experimental and theoretical advances in the quantum mechanics of electrical circuits and in the manipulation of nanomechanical systems via radiation pressure forces. Motivated by the recent experimental progress in 'circuit QED,' the PI will continue his productive collaboration with the Yale experimental group of Schoelkopf and Devoret to realize novel and fundamental strong-coupling quantum optics in microwave electrical circuits. The PI will develop theoretical models of the many-body physics of strongly-interacting microwave polaritons in lattices of superconducting qubits and resonators. Such lattices can be used to simulate strongly-correlated bosons as well as frustrated quantum spins.Axions are elementary particles proposed to exist by theory which are important candidates to explain the cold dark matter which pervades the universe. In the presence of a strong magnetic field they are predicted to decay into microwave photons. Circuit QED advances are approaching the point where they could dramatically change the way axion dark matter searches are done. In light of recent experimental advances, the PI will evaluate the efficacy of different possible approaches to optimizing microwave photon detection in axion searches.The PI will also continue collaborations on opto-nano-mechanics with the Yale experimental groups of Jack Harris and Hong Tang and begin collaboration with new faculty member Peter Rakich. A new direction with Harris will be development of models of the opto-mechanics of whispering gallery modes of deformable levitated drops of liquid helium. Another will be collaboration with Rakich on the theoretical and practical limits of narrow line widths which can be achieved in on-chip optomechanical Brillouin lasers. Applications and extensions of quantum optics ideas for superconducting circuits and opto-mechanical systems will be developed. A new direction will be to propose and develop new ideas for quantum bath engineering which will create 'friction' with the aim to naturally relax quantum systems, not towards their ground states, but rather towards pre-determined entangled many-body states of interest. Such ideas will likely be broadly applicable beyond superconducting qubits to include atomic physics systems and other types of quantum bits and to quantum simulations. This work has a strong interdisciplinary component which brings together ideas and methods used in the condensed matter, atomic physics, and quantum optics communities. The close collaboration of the PI with experimental groups is leading to new precision microwave measurement techniques at the single photon level which will have applications beyond quantum information processing to probing nanoscale systems generally, and is yielding new forms of ultra-low-noise microwave amplifiers and detectors.NONTECHNICAL SUMMARYThis award supports theoretical research and education on artificial atoms created from electrical circuits made from materials that are superconductors. Superconductors exhibit a quantum mechanical state which can conduct electricity without dissipation. Like real atoms, these artificial atoms can interact with a single quantum or photon of microwave radiation. These superconducting electrical circuits are being developed as the basic hardware for the construction of a quantum computer. A quantum computer would perform computations by manipulating quantum mechanical states and in principle can dramatically outperform the fastest existing computers for some problems. In addition to this potential practical application, these superconducting circuits can be used to efficiently detect individual microwave photons. The PI will explore applications of this new capability to the improved detection of axions, elementary particles postulated to solve the 'dark matter' problem of cosmology and astrophysics.The PI will also continue his study of the theory of opto-mechanics in which the feeble pressure exerted by light can be used to cause mechanical motion of small objects and even cool their motion. This is opening up a whole new technology with practical applications in optical communications and measurements. Of particular fundamental interest will be exploration with experimental colleagues of new ideas for applying radiation pressure of light to move and distort magnetically levitated drops of superfluid helium.