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arXiv · 2602.01934

Exceptional phase transition in a single Kerr-cat qubit

Pei-Rong Han·Tian-Le Yang·Wen Ning·Hao-Long Zhang·Huifang Kang·Huiye Qiu·Zhen-Biao Yang
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Abstract

Exceptional points in non-Hermitian quantum systems give rise to novel genuine quantum phenomena. Recent explorations of exceptional-point-induced quantum phase transitions have extended from discrete-variable to continuous-variable-encoded quantum systems. However, quantum phase transitions driven by Liouvillian exceptional points (LEPs) in continuous-variable platforms remain largely unexplored. Here, we construct and investigate a Liouvillian exceptional structure based on a driven-dissipative Kerr-cat qubit. Through numerical simulations, we reveal a quantum phase transition occurring at the LEP characterized by a sudden change in dynamical behavior from underdamped oscillations to overdamped relaxations as visualized via Wigner functions and Bloch sphere trajectories. Notably the negativity of the Wigner function serves as a direct signature of genuine quantum coherence unattainable in conventional single-qubit non-Hermitian systems. Furthermore, we introduce the phase difference between the off-diagonal elements of the Liouvillian eigenmatrices as a novel parameter to quantify the transition. Our results establish the Kerr-cat qubit as a novel continuous-variable setting for exploring dissipative quantum criticality and intrinsic non-Hermitian physics.

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Pei-Rong Han, Tian-Le Yang, Wen Ning, Hao-Long Zhang, Huifang Kang, Huiye Qiu, Zhen-Biao Yang. 2026-02-02. Exceptional phase transition in a single Kerr-cat qubit. https://arxiv.org/abs/2602.01934

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