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arXiv · 2512.10921

Qubit decoherence in dissipative two-photon resonator: real-time instantons and Wigner function

V. Yu. Mylnikov·S. O. Potashin·Alex Kamenev
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Abstract

We study the quantum dynamics of a single bosonic cavity subject to two-photon driving and two-photon dissipation in the presence of finite detuning. Exploiting a hidden time-reversal symmetry, the Wigner representation and the WKB method, we introduce an effective phase-space potential for description of the steady state. It reveals two attracting points, which are metastable due to quantum fluctuations. By employing the Keldysh real-time path integral formalism, we compute the instanton trajectory governing the quantum activation process between these attractors and establish a fundamental connection with the Wigner representation. This relation unifies the steady-state phase-space description with dynamical quantum activation processes. We also derive an analytical expression for the decoherence rate of the system. Our work provides a coherent theoretical framework for analyzing quantum bistability, metastability, and decoherence in driven-dissipative nonlinear resonators, with direct implications for the design of bosonic qubits and quantum information processing.

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V. Yu. Mylnikov, S. O. Potashin, Alex Kamenev. 2025-12-11. Qubit decoherence in dissipative two-photon resonator: real-time instantons and Wigner function. https://arxiv.org/abs/2512.10921

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