Quantum optical resonators: a building block for quantum computing and sensing systems

量子光学谐振器：量子计算和传感系统的构建模块量子效应有可能彻底改变计算、通信和测量系统。 光子特别适合量子信息（通常称为量子位）的通信，因为光子可以长距离传输，而信息损失最小。 然而，利用光子实现量子计算机一直具有挑战性，因为一个光子无法轻易控制另一个光子。幸运的是，Knill、Laflamme 和 Milburn (KLM) 发现，当光子在分束器等线性光学元件内发生干涉并被检测到时，可以实现对另一个光子的有效控制。然而，这一突破的代价是需要许多额外的光学设备，这些设备占用了大型光学平台上的大量空间，因此迄今为止限制了量子光学计算机的性能。最近，人们尝试将量子光学器件小型化到微芯片上，以便密集集成所有必要的组件并最大限度地提高性能。 在该项目中，通过开发基于谐振光学腔的新型量子光学器件，量子光学电路的占地面积将进一步显着减少。这些谐振器有效地迫使光子在几微米的小空间内多次传播。研究小组最近发现，当仅用几个光子激发谐振器时，光子就会以令人惊讶的新方式干涉量子光学。具体来说，这种新的量子共振干涉取决于光子激发本身，为开发新的量子计算门提供了可能性。此外，人们还发现这种量子干涉比传统光学元件（例如分束器）更加稳健。这些量子光学谐振器还可用于将用于生物、化学和环境传感的光学传感器的灵敏度提高一倍以上。该项目的主要目标是实现基于谐振量子光逻辑门的可扩展量子光计算电路。研究小组最近表明，在量子状态下工作的环形谐振器表现出取决于光子态的谐振响应。与仅使用一组参数以最大保真度工作的分束器不同，环形谐振器中的这种独特的无源反馈有效地确保了无限设备参数空间上的高保真度量子干涉。该器件尺寸紧凑，并且能够在低能耗的情况下动态重新配置，确保环形谐振器成为实现复杂量子光学电路的理想构建模块。该项目将取得以下关键进展：（1）环形谐振腔中鲁棒量子干涉的实验演示。具体来说，它将表明，当两个光子在环形谐振器内相互作用时，会发生一种新颖的红欧曼德尔（HOM）共振，其中两个光子可以聚集在一起或保持分开。 （2）将开发第一个基于谐振器的通用量子逻辑门。我们还将探索逻辑门可以操作的参数空间，以提高整体电路的鲁棒性。 (3) 谐振器中的多光子干涉将用于增强传感。具体来说，谐振器的量子相位响应的变化比经典光的变化要强烈得多。这可用于实现超灵敏的生物、化学和环境传感器。

Quantum optical resonators: a building block for quantum computing and sensing systemsQuantum effects have the potential to revolutionize computing, communication and measurement systems. Photons are particularly well suited for the communication of quantum information, commonly known as qubits, since photons can transmit over long distances with minimal information loss. However, it has been challenging to use photons to realize quantum computers since one photon cannot easily control another photon. Fortunately, it was discovered by Knill, Laflamme and Milburn (KLM) that when photons interfere within linear optical elements, such as beam splitters, and are then detected that it is possible to realize an effective control of another photon. However, this breakthrough comes at the cost of requiring many additional optical devices that take up a lot of space on large optical tables, and as a result, have limited the performance of quantum optical computers so far. Recently, attempts have been made to miniaturize quantum optical devices onto microchips in order to densely integrate all of the necessary components and to maximize performance. In this project, the footprint of quantum optical circuits will be significantly reduced further through the development of a new class of quantum optical devices based on resonant optical cavities. These resonators effectively force photons to propagate many times around in a small space of just a few micrometers. The research team recently discovered that when the resonators are excited with just a few photons that the photons interfere quantum optically in surprising new ways. Specifically, this new quantum resonant interference depends on the photon excitation itself, opening up the possibility to develop new quantum computing gates. Furthermore, it has been found that this quantum interference is more robust than in traditional optical components, such as beam splitters. These quantum optical resonators can also be used to more than double the sensitivity of optical sensors used for biological, chemical and environmental sensing. The primary goal of the project is to realize scalable quantum optical computing circuits based on resonant quantum optical logic gates. The research team has recently shown that ring resonators operating in the quantum regime exhibit a resonant response that depends on the photon state. Unlike beam splitters, which operate with maximum fidelity with only one set of parameters, this unique passive feedback in ring resonators ensures high fidelity quantum interference over, effectively, an infinite device parameter space. The devices compact size and ability to be reconfigured dynamically with low energy requirements ensures that ring resonators are the ideal building block for realizing complex quantum optical circuits. In this project the following key advancements will be made: (1) Experimental demonstration of robust quantum interference in a ring resonator. Specifically, it will be shown that when two photons interact within a ring resonator a novel Hong-Ou-Mandel (HOM) resonance occurs where the two photons can either bunch together or stay apart. (2) The first universal quantum logic gates based on resonators will be developed. And the parameter space that the logic gates can operate over will be explored with the goal of increasing overall circuit robustness. (3) Multi-photon interference in resonators will be used to enhance sensing. Specifically, the quantum phase response of the resonator can vary much more strongly than with classical light. This can be used to realize ultra-sensitive biological, chemical and environmental sensors.