Condensed Matter and Quantum Information Theory

该奖项支持理论量子物理学的研究和教育，重点是研究在微波频率和接近绝对零度的温度下工作的电路的量子特性。PI研究的不是激光、光频光子和单个真实的原子，而是微波光子和由超导电路元件构造的人造原子。由于人造原子（称为量子比特）比单个的真实的原子大得多，它们与光子的相互作用可能比普通光与原子之间的相互作用大得多。这允许在全新的机制中测试量子力学的含义，以及创建量子比特和光子的奇异量子态，这些量子态可以用作构建量子计算机和基于光子传输的安全量子通信的基础。该项目还将开发和研究使用光子存储和忠实传输量子信息的方法，即使光子在长距离传输或在量子存储器中长时间存储期间丢失。由于最近的巨大实验进展，现在有可能以前所未有的灵敏度探测单个光子。该项目将利用这些进展提出方法，大大加快对某类暗物质粒子（称为轴子）的搜索，这将在凝聚态物理学和宇宙学领域之间建立重要的新联系。最后，PI将继续与实验同事合作研究量子光学力学，利用微弱的光辐射压力来控制机械物体的运动，并以前所未有的精度进行位置测量。最近在LIGO上发现的引力波是这类研究的实际应用之一。该项目将通过其跨学科性质和与实验的密切合作产生更广泛的影响。PI正在促进凝聚态，原子物理，量子光学和电气工程社区之间的沟通。作为该项目的一部分，博士后研究员将接受尖端理论方法的培训。PI还负责为来自新英格兰的大约200名高中生举办年度讲座，作为耶鲁物理奥林匹克的一部分，重点是解释量子力学和量子信息处理的思想。技术总结该奖项支持理论量子物理的研究和教育，重点是量子光学和腔量子电动力学到电路QED的思想的应用。该项目涉及四个主要研究领域：1）超导量子比特与多模腔的强耦合：该项目将研究一米长谐振器的自由光谱范围小到足以与量子比特与谐振器的真空拉比耦合相媲美的极限中的非线性量子光学。因此，许多模式共同耦合到量子比特，从而相互耦合。2）有效检测微波光子的轴子纠缠和远程纠缠：这个项目将提出和开发新的方法，使用电路QED的工具来检测宇宙学轴子暗物质粒子。将分析两种不同的方案，第一种使用双模压缩器来放大轴子信号而不放大真空噪声，第二种使用最近开发的微波光子量子非破坏检测能力来创建微波光子的“光电倍增管”。PI将开发一种最佳贝叶斯滤波器，以最大限度地减少检测器的暗计数率，从而大大提高相对于当前方法检测轴子的信噪比。同样的想法可以应用于量子比特在独立腔中的远程纠缠，这将在量子计算机的发展中具有重要的应用。3）用于量子存储器和通信的可纠错光子码：该项目位于基础量子信息理论中。它将利用新的实验能力，这些能力允许基本上通用的控制和测量少量微波光子和超导量子比特的福克态的复杂叠加，并且在普通光学中没有类似物。PI将开发玻色子模式的近似连续量子纠错协议。这些将应用于使用微波谐振器作为量子存储器，使用微波光子进行量子通信，以及将存储在微波光子中的量子信息忠实地转换为光学频率，以便通过光纤网络进行长距离传输。PI特别感兴趣的是在参数空间中所谓的“例外点”附近的非绝热演化的全量子理论的发展。该项目将通过其跨学科性质和与实验的密切合作产生更广泛的影响。PI正在促进凝聚态，原子物理，量子光学和电气工程社区之间的沟通。作为该项目的一部分，博士后研究员将接受尖端理论方法的培训。PI还负责为来自新英格兰的大约200名高中生举办年度讲座，作为耶鲁物理奥林匹克的一部分，重点是解释量子力学和量子信息处理的思想。

NONTECHNICAL SUMMARYThis award supports research and education in theoretical quantum physics focusing on the study of the quantum properties of electrical circuits operating at microwave frequencies and at temperatures close to absolute zero. Rather than dealing with lasers, photons at optical frequencies, and individual real atoms, the PI studies microwave photons and artificial atoms constructed from superconducting circuit elements. Because the artificial atoms (called qubits) are enormously larger than individual real atoms, their interaction with photons can be significantly larger than the interaction between ordinary light and atoms. This permits testing the implications of quantum mechanics in completely new regimes, as well as creating exotic quantum states of qubits and photons, which can be used as the basis for building a quantum computer and for secure quantum communication based on the transmission of photons. This project will also develop and study methods for storing and faithfully transmitting quantum information using photons, even if photons are lost during transmission over long distances or during storage over long periods of time in a quantum memory. Because of recent enormous experimental progress, it is now possible to detect individual photons with unprecedented sensitivity. This project will take advantage of these advances to propose methods that will dramatically speed up the search for a certain class of dark matter particles known as axions, which will forge important new connections between the fields of condensed matter physics and cosmology.Finally, the PI will continue his collaboration with experimental colleagues to study quantum optomechanics, in which the feeble radiation pressure of light is harnessed to control the motion of mechanical objects, and make position measurements with unprecedented accuracy. The recent discovery of gravitational waves at LIGO is an example of one of the practical applications for this type of research.The project will achieve broader impacts by its interdisciplinary nature and the close collaboration with experiment. The PI is fostering communication among the condensed matter, atomic physics, quantum optics and electrical engineering communities. As part of the project a postdoctoral fellow will be trained in cutting-edge theoretical methods. The PI is also responsible for an annual lecture for approximately 200 high-school students from across New England as part of the Yale Physics Olympics, focused on explaining ideas from quantum mechanics and quantum information processing.TECHNICAL SUMMARYThis award supports research and education in theoretical quantum physics focusing on the application of ideas from quantum optics and cavity quantum electrodynamics to circuit QED. The project involves four main areas of research: 1) Strong-coupling of a superconducting qubit to a multi-mode cavity: This project will study nonlinear quantum optics in the limit where the free spectral range of a one-meter-long resonator is small enough to be comparable to the vacuum Rabi coupling of a qubit to that resonator. Thus, many modes are jointly coupled to the qubit and hence to each other.2) Efficient Detection of Microwave Photons for Axion Searches and Remote Entanglement: This project will propose and develop novel methods to use tools from circuit QED to detect cosmological axion dark-matter particles. Two different schemes will be analyzed, the first using two-mode squeezers to amplify the axion signal without amplifying the vacuum noise, and the second using recently developed capabilities for quantum non-demolition detection of microwave photons to create a "photomultiplier" for microwave photons. The PI will develop an optimal Bayesian filter to minimize the dark count rate of the detector and hence dramatically increase the signal-to-noise ratio for the detection of axions relative to current methods. The same ideas can be applied to the remote entanglement of qubits in independent cavities, which will have important application in the development of quantum computers.3) Error Correctable Photonic Codes for Quantum Memories and Communication: This project sits within fundamental quantum information theory. It will take advantage of new experimental capabilities, which allow essentially universal control and measurement of complex superpositions of Fock states of small numbers of microwave photons and superconducting qubits, and have no analog in ordinary optics. The PI will develop approximate continuous quantum error correction protocols for bosonic modes. These will have applications to using microwave resonators as quantum memories, to quantum communication using microwave photons, and to faithful conversion of quantum information stored in microwave photons up to optical frequencies where it can be transmitted large distances over fiber networks.4) Optomechanics: This is a fundamental quantum optics collaboration with experimental colleagues at Yale. The PI is particularly interested in the development of a fully quantum theory of non-adiabatic evolution near so-called "exceptional points" in the parameter space. The project will achieve broader impacts by its interdisciplinary nature and the close collaboration with experiment. The PI is fostering communication among the condensed matter, atomic physics, quantum optics and electrical engineering communities. As part of the project a postdoctoral fellow will be trained in cutting-edge theoretical methods. The PI is also responsible for an annual lecture for approximately 200 high-school students from across New England as part of the Yale Physics Olympics, focused on explaining ideas from quantum mechanics and quantum information processing.