Harnessing two-photon dissipation for enhanced quantum measurement and control

Abstract

Dissipation engineering offers a powerful tool for quantum technologies. Recently, new superconducting devices have achieved an engineered two-photon dissipation rate exceeding all other relevant timescales. In particular, they have proven most useful in preventing transitions between the logical states $|\pm\alpha\rangle$ of a cat qubit. Here, we present three key applications of strong two-photon dissipation for quantum measurement and control, beyond cat qubit stabilization. Firstly, we demonstrate its efficacy in overcoming limitations encountered in Wigner tomography at high photon numbers. Secondly, we showcase its potential for realizing universal gates on cat qubits, exploiting the coherent mapping between cat qubit states and superpositions of 0 and 1 photons. Finally, we harness the transient dynamics of a cat state under two-photon dissipation to prepare squeezed cat states with a squeezing factor exceeding 3.96$\pm$0.07 dB.