CQIS: A Quantum Electro-Optic Converter

量子信息科学为计算、传感和通信提供了全新的、强大得多的范例。它还需要能够处理量子信号的新类型的设备。工程化量子系统的一种有希望的方法是使用低温超导电路来执行量子信息处理。这些量子机器目前正在世界各地的学术、政府和工业实验室中积极开发。然而，在保持它们重要的量子特性的同时，没有办法将这些系统相互连接起来，跨度超过几英寸。要创建跨越更长距离并离开量子比特低温环境的链路，需要将量子信息从适合处理的形式转换为另一种适合传输的形式，反之亦然。事实上，所有的计算、传感和通信系统都依赖于将信息从一种形式转换成另一种形式的设备。量子领域缺乏这种能力，阻碍了真正令人信服的量子技术的出现，这些技术承诺执行超出当今技术手段的任务。拟议的研究工作的重点是创造这样一种能力，以应对工程科学中的一个基本和长期的挑战。该计划将开发和演示一种设备，可以在保持其重要量子属性的同时，转换电磁频谱中的量子信息。这样一种设备，量子电光转换器，将在能够远距离传输的光学光子和低温超导电路中的微波光子之间转换信息，这些低温超导电路被用来实现第一台量子计算机。就像实现互联网的电光调制器一样，量子电光转换器有朝一日可能会使量子互联网成为可能。这项研究的目标是开发一种可以在光学和微波频率之间相互转换量子信息的设备。该方法是在同一电光衬底上制作高Q值光学腔和微波超导腔，在Nb酸锂上异质集成硅，并在这两个腔中产生激发相互作用。为了实现这一点，将使用最近开发的创建高Q电光光子晶腔的技术，制造具有非常低杂散电容的高Q超导电感的技术，以及对完美量子态转换方法的理论见解。PI的实验室将通过先进和综合光子学、异质集成、超导电路以及低温光学和微波实验的技术来开发量子电光转换器技术，以实现这一愿景。在这个项目中开发的量子电光转换器承诺1)将这些量子机相互连接，2)允许光学访问微波频率下的量子非线性，3)通过允许在光纤上多路复用许多微波信号，简化它们对更大数量的超导量子比特的缩放。这将对实验量子信息科学产生重大影响。最后，该设备将首次展示使用激光对微波电路进行量子光学控制，这将使新型和意想不到的类型的量子传感和通信能力在微波频率上得以实现。

Quantum information science promises fundamentally new and vastly more powerful paradigms of computation, sensing, and communications. It also necessitates new classes of devices that are capable of processing quantum signals. One promising approach to engineered quantum systems uses low-temperature superconducting circuits to perform quantum information processing. These quantum machines are now being developed actively in academic, government, and industrial labs around the world. However, there is no way to connect these systems to one another across more than a few inches while preserving their important quantum properties. Creating links that traverse longer distances and leave the low temperature environments of the qubits demands converting the quantum information from a form suited for processing to another form suited for transmission, and vice versa. In fact, all computation, sensing, and communication systems depend on devices that convert information from one form to another. The lack of this capability in the quantum domain impedes the emergence of truly compelling quantum technologies that promise to perform tasks beyond the means of today's technologies. The proposed research effort is focused on creating such a capability to address a basic and long-standing challenge in engineering science. The program will develop and demonstrate a device that can convert quantum information across the electromagnetic spectrum while preserving its important quantum properties. Such a device, a quantum electro-optic converter, will convert information between optical photons capable of travelling long distances, and microwave photons in low-temperature superconducting circuits being used to implement the first quantum computers. Much like the electro-optic modulators that enable the Internet, quantum electro-optic converters may someday enable the quantum Internet.The objective of this research is to develop a device that can interconvert quantum information between optical and microwave frequencies. The approach is to fabricate high-Q optical cavities and microwave superconducting cavities on the same electro-optical substrate, heterogeneously integrated silicon on lithium niobate, and to generate interactions between excitations in the two cavities. To achieve this, recently developed techniques for creating high-Q electro-optic photonic crystal cavities, techniques for making high-Q superconducting inductors with very low stray capacitance, as well as theoretical insight on perfect quantum state conversion methods will be used. The PI's lab will develop the technology for quantum electro-optic converters by advancing and synthesizing techniques from photonics, heterogeneous integration, superconducting circuits, and cryogenic optical and microwave experiments to realize this vision. The quantum electro-optic converter being developed in this program promises to 1) connect these quantum machines to each other, 2) allow optical access to quantum nonlinearities at microwave frequencies, and 3) to simplify their scaling to larger numbers of superconducting qubits by allowing multiplexing of many microwave signals over an optical fiber. This will have a major impact on experimental quantum information science. Finally, the device will demonstrate for the first time quantum optical control of microwave circuits using laser light, which can enable new and unforeseen types of quantum sensing and communications capabilities at microwave frequencies.