Microwave quantum optics on superconducting circuits

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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.