Section: New Results

Continuous generation and stabilization of mesoscopic field superposition states in a quantum circuit

Participants : Ananda Roy, Mazyar Mirrahimi.

While dissipation is widely considered as being harmful for quantum coherence, it can, when properly engineered, lead to the stabilization of non-trivial pure quantum states. In a close collaboration with the teams of Michel Devoret and Douglas Stone (Department of Applied Physics, Yale University), and in the framework of a 6 months visit by Ananda Roy (PhD student at Yale), we proposed a scheme for continuous generation and stabilization of Schrödinger cat states in a cavity using dissipation engineering [15] . The scheme consists in first generating non-classical photon states with definite parity by means of a two-photon drive and dissipation, and then stabilizing these transient states against single-photon decay. The single-photon stabilization is autonomous, and is implemented through a second engineered bath, which exploits the photon number dependent frequency-splitting due to Kerr interactions in the strongly dispersive regime of circuit QED. Starting with the Hamiltonian of the baths plus cavity, we derived an effective model of only the cavity photon states along with analytic expressions for relevant physical quantities, such as the stabilization rate. The deterministic generation of such cat states is one of the key ingredients in performing universal quantum computation.