Microwave quantum optics on superconducting circuits

我在本财年的工作包括开发一种向一维波导发射微波光子的单向发射器。这项工作对于制造一维量子网络的前景特别感兴趣，在这种网络中，耦合到公共波导的量子比特可以相互交换量子信息。事实上，如果没有某种特定的设计来导致单方向的发射，无论是向右还是向左，一个量子比特将自然地在波导的两个方向上发射，从而将量子信息分散在不同的位置。吸收也是如此。如果来自波导的光子从单一方向撞击通常的量子比特，该量子比特将不能吸收全部光子。另一方面，我提出的设备可以单向吸收和发射光子，这让我们可以绕过这个问题。目前的目标是演示这些单向设备中的单个设备与开放的传输线相耦合的操作。我的大部分时间都花在从理论角度预测我们正在考虑的系统的行为上。通过将系统的物理编码成矩阵和方程，我们可以计算给定物理系统在时间上的时间演化，并推导出它在未来某个时间的状态。所有这些模拟都是使用Python编程语言进行的。

My work in this fiscal year consisted in developing a unidirectional emitter of　microwave photons to a 1D waveguide. This work is of particular interest　regarding the prospect of fabricating 1D quantum networks, where qubits coupled to a common waveguide can exchange quantum information with one another. Indeed, without some specific design that will lead to emission in a single direction, right or left, a qubit will naturally emit in both directions of the waveguide, which will thus scatter the quantum information in different locations. The same goes for absorption. If a photon from the waveguide impinges on a usual qubit from a single direction, the qubit will not be able to absorb the full photon. The device I propose, on the other hand, can absorb and emit photons unidirectionally, which allows us to circumvent this issue. The aim for now is to demonstrate the operation of a single of those unidirectional devices, coupled to an open transmission line. A large part of my time was devoted to predicting the behaviour of the systems we are considering from a theoretical point of view. By encoding the system’s physics into matrices and equations, we can calculate the time-evolution of a given physical system in time and deduce what will be its state at a future time. All these simulations were made using the Python programming language.