Spectroscopy of Quantum Phase Slips: Visualizing Complex Real-Time Instantons

• URL: http://arxiv.org/abs/2512.24495v1
• Date: Tue, 30 Dec 2025 22:35:03 GMT
• Title: Spectroscopy of Quantum Phase Slips: Visualizing Complex Real-Time Instantons
• Authors: Foster Thompson, Daniel K. J. Boneß, Mark Dykman, Alex Kamenev,
• Abstract summary: In this work, we show that the phase-slip rate is exponentially sensitive to weak AC perturbations.<n>The spectrum of the system's response -- captured by the so-called logarithmic susceptibility (LS) -- enables a direct observation of characteristic features of real-time instantons.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Parametrically driven oscillators can emerge as a basis for the next generation of qubits. Classically, these systems exhibit two stable oscillatory states with opposite phases. Upon quantization, these states turn into a pair of closely spaced Floquet states, which can serve as the logical basis for a qubit. However, interaction with the environment induces phase-slip events which set a limit on qubit coherence. Such phase slips persist even at zero temperature due to a mechanism known as quantum activation \cite{QuantumActivation}. In contrast to conventional tunneling, the quantum activation is described by a {\em real-time} instanton trajectory in the complexified phase space of the system. In this work, we show that the phase-slip rate is exponentially sensitive to weak AC perturbations. The spectrum of the system's response -- captured by the so-called logarithmic susceptibility (LS) -- enables a direct observation of characteristic features of real-time instantons. Studying this spectrum suggests new means of efficient qubit control.

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