Hybrid Quantum System of Excitons and Superconductors

在过去的10年里，量子计算已经成为主流——实验从大学研究实验室扩展到工业研发，由bb0、微软和IBM等科技巨头领导。在引擎盖下，许多这些复杂的机器依靠超导电路来存储和操纵量子信息。这些设备的工作频率与现代经典cpu的时钟速度相似——大约几GHz。这个频率，或者能量，比室温下的要小得多，所以为了消除热噪声，在量子状态下工作，这些设备必须冷却到绝对零度以上的千分之几度。虽然这对于单个处理器来说是可能的，但要实现构建量子网络所需的千米尺度要困难得多。为了克服这个问题，微波量子信息需要被上转换成可以通过光纤或卫星发送的光信号。挑战在于在不引入可能破坏脆弱量子态的额外退相干的情况下有效地做到这一点。在这里，我们建议用里德伯激子来建造这样一个转换器——里德伯激子是一种“准粒子”，具有类似原子的能级谱，存在于一种叫做氧化亚铜的半导体材料中。里德伯激子为光学和微波场提供了强耦合，并且很容易在超导量子器件中使用的超冷温度下制备。我们的小组最近成为第一个使用里德伯激子将微波信号映射到光上的小组，在这个提议中，我们将把这项工作扩展到量子体制。我们将开发将里德伯激子和超导电路物理集成在一起所需的方法，并研究如何最大限度地提高它们之间的耦合，以及解决在转换过程中减少光损耗的挑战。

In the last 10 years, quantum computing has gone mainstream - with experiments expanding out of university research labs and into industrial R&D, led by technological giants like Google, Microsoft and IBM. Under the bonnet, many of these sophisticated machines rely on superconducting circuits to store and manipulate the quantum information. The operating frequency of these devices is similar to the clock speed of modern classical CPUs - around a few GHz. This frequency, or energy, scale is much, much smaller than that associated with room temperature, and so to get rid of thermal noise and operate in the quantum regime these devices must be cooled to a few thousandths of a degree above absolute zero. While this is possible for a single processor, it is much harder to achieve over the kilometre scales required to build a quantum network.To overcome this problem, the microwave quantum information needs to be up-converted to an optical signal that can be sent down an optical fibre, or via a satellite. The challenge is to do this efficiently without introducing additional decoherence that might destroy the fragile quantum state. Here we propose to build such a converter using Rydberg excitons - a ``quasi-particle'' with an atom-like spectrum of energy levels that exists inside a semiconducting material called cuprous oxide. Rydberg excitons provide strong coupling to optical and microwave fields and are easily prepared at the ultracold temperatures used in superconducting quantum devices. Our consortium recently became the first group to use Rydberg excitons to map a microwave signal onto light, and in this proposal, we will extend this work into the quantum regime. We will develop the methods required to physically integrate Rydberg excitons and superconducting circuits together, and study ways to maximise the coupling between them, as well as tackling the challenge of reducing optical losses in the conversion process.