Quantum Microwaves from Superconducting Quantum Circuits

超导量子电路是基础和应用量子研究的成熟平台，谷歌、英特尔、D-Wave和IBM以及北美、欧洲和亚洲各国政府的重大投资就是明证。在这项发现资助的支持下，我们将为世界范围内利用这项令人兴奋的技术做出重要贡献。模拟量子模拟是一种范例，其中量子电路被构造成直接模仿或“模拟”感兴趣的系统。 其原理与使用简单的半导体电路来模拟火箭的轨迹相同，这在20世纪60年代数字计算能力变得廉价之前很常见。 同样，在大规模数字量子计算机问世之前，模拟量子模拟是释放量子计算潜在优势的一条有前途的途径。 作为第一个测试平台，我们将模拟强相互作用的量子场论。这些理论描述了量子色动力学等基本模型，但也描述了一系列技术上重要的量子材料，如高温超导体。** 光量子计算与参量腔光量子计算（OQC）是量子信息的一个主要范例。在标准的OQC中，量子信息是通过在大桌面上行进的激光来处理的。我们将使用在集成电路芯片上传播的微波。本课题组研制的参量腔是利用微波光子进行片上OQC的一个很有前途的平台。 我们已经展示的功能实现了线性量子光学的所有工具。然而，已经表明，即使是一组完整的线性运算也不能给出量子加速。 需要所谓的非高斯态作为输入来实现量子优势。特别令人感兴趣的是一种“神奇状态”，被称为双相态，它对实验者来说仍然是难以捉摸的。 我的团队最近取得的进展使我们能够证明这种神奇状态的重要组成部分。我们将继续我们的工作，以产生一个有用的魔术状态和发展片上OQC。** 量子照明（QI）最近作为提高雷达灵敏度的可能途径而受到关注。 QI应用了一种独特的量子效应，称为纠缠。与许多潜在的量子应用不同，QI似乎对传输过程中的噪声和损耗非常鲁棒，这表明它可能具有实际应用。最近的实验已经证明了QI在光频的基本原理。这是一个重要的原理证明，但传统的雷达系统通常使用微波频率。我们的参量腔也是QI所需的纠缠微波光子的极好来源。我们将建立在我们现有的结果，以证明微波QI在环境条件下。证明环境微波的量子优势将是一个重要的突破。*****

Superconducting quantum circuits are a well-established platform for both fundamental and applied quantum research, as evidenced by major investments from Google, Intel, D-Wave and IBM, as well as by governments across North America, Europe and Asia. Supported by this Discovery grant, we will make important contributions to the world-wide effort to exploit this exciting technology.******Analog quantum simulation is a paradigm where a quantum circuit is constructed to directly mimic or “simulate” a system of interest. The principle is the same as using a simple semiconductor circuit to simulate the trajectory of a rocket, as was common through the 1960s before digital computing power became inexpensive. Similarly, analog quantum simulation is a promising path to unlock the potential advantages of quantum computing before large-scale digital quantum computers become available. As a first testbed, we will simulate strongly-interacting quantum field theories. These theories describe fundamental models such as quantum chromodynamics, but also a wide array of technologically important quantum materials such as high-temperature superconductors. ******Optical Quantum Computing with Parametric Cavities Optical quantum computing (OQC) is a major paradigm of quantum information. In standard OQC, quantum information is processed by laser light traveling on a large table top. We would instead use microwaves traveling on chip in an integrated circuit. The parametric cavities developed by my group are a promising platform for on-chip OQC using microwave photons. The functionality we have already demonstrated implements all the tools of linear quantum optics. However, it has been shown the even a complete set of linear operations cannot give a quantum speedup. So-called non-Gaussian states are needed as inputs to achieve a quantum advantage. Of particular interest is a type of “magic state,” called the cubic-phase state, which has remained elusive to experimenters. Recent advances by my group have allowed us to demonstrate important building blocks of this magic state. We will continue our work to produce a useful magic state and develop on-chip OQC. ******Quantum illumination (QI) has recently gained attention as a possible avenue to improve the sensitivity of radar. QI applies a unique quantum effect, called entanglement. Unlike many potential quantum applications, QI seems to be very robust to noise and losses during transmission, suggesting that it may have practical applications. Recent experiments have demonstrated the basic principle of QI at optical frequencies. This is an important proof of principle, but conventional radar systems typically use microwave frequencies. Our parametric cavities are also an excellent source of the entangled microwave photons need for QI. We will build on our existing results to demonstrate microwave QI in ambient conditions. Demonstrating a quantum advantage for ambient microwaves would be an important breakthrough. *****