Controlled-squeeze gate in superconducting quantum circuits

Abstract

We present a method to prepare nonclassical states of the electromagnetic field in a microwave resonator. It isbased on a controlled gate that applies a squeezing operation on a SQUID-terminated resonator conditioned onthe state of a dispersively coupled qubit. This controlled-squeeze gate, when combined with Gaussian operationson the resonator, is universal. We explore the use of this tool to map an arbitrary qubit state into a superpositionof squeezed states. In particular, we target a bosonic code with well-defined superparity which makes photonlosses detectable by nondemolition parity measurements. We analyze the possibility of implementing this usingstate-of-the-art circuit QED tools and conclude that it is within reach of current technologies.