On generating propagating grid states from superconducting circuits

Abstract

Due to current advancements in quantum technologies, quantum processors are growing in size, and we enter into the distributed quantum computing era. Distributed quantum computing is based on sharing information between several spatially distributed processors. This is achieved by sending photons carrying the quantum information between two or more distant quantum processors. Since we want all communication to be secure and tolerant against unavoidable noise in the communication channel, one attractive possibility is to encode the quantum information in error correctable quantum states, e.g. GKP states, Schrödinger cat states. The goal with error correctable states is to compensate for errors and loss in our communication channels. Previously it has been shown that optional encoding of quantum information from a processor into a quantum propagating mode makes the output field multimode, i.e. it consists of a combination of single mode states with different temporal envelopes. As a solution to this problem, we study the generation of error correctable quantum states, specifically GKP states, in highly lossy quantum circuits to prepare it as a traveling state in a waveguide instead of in the system. In this thesis, we present the basic theory for the preparation protocol; optimal release and the necessary extensions to compensate for noise. We study the character of the output field, as well as restrictions of this methodology.