Qubit Decoherence and Symmetry Restoration through Real-Time Instantons

Abstract

A parametrically driven quantum oscillator, stabilized by a nonlinear dissipation, exhibits a spontaneous breaking of the parity symmetry. It results in the quantum bi-stability, corresponding to a Bloch sphere of dark states. This makes such a driven-dissipative system an attractive candidate for a qubit. The parity symmetry breaking is exact both on the classical level and within the quantum mechanical perturbation theory. Here we show that non-perturbative quantum effects lead to the symmetry restoration and result in exponentially small but finite qubit decoherence rate. Technically the symmetry restoration is due to real time instanton trajectories of the Keldysh path integral, which represents the Lindbladian evolution of the driven-dissipative oscillator.

7 pages, 2 figures

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Cited by in corpus (4)

• Bit-flip errors in dissipative cat qubits: second-order perturbation theory
• A Real-time Instanton Approach to Quantum Activation
• Synchronizing microwave cQED limit-cycle oscillators
• Non-perturbative switching rates in bistable open quantum systems: from driven Kerr oscillators to dissipative cat qubits