Critical Unstable Qubits in Particle Physics

• URL: http://arxiv.org/abs/2603.12061v1
• Date: Thu, 12 Mar 2026 15:28:18 GMT
• Title: Critical Unstable Qubits in Particle Physics
• Abstract summary: We study in detail the dynamics of unstable two-level quantum systems by adopting the Bloch-vector representation.<n>We find that critical unstable qubit systems exhibit atypical behaviours like coherence--decoherence oscillations.<n>We provide a compilation table of all well-explored meson--antimeson two-level systems in terms of Bloch-sphere parameters.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We study in detail the dynamics of unstable two-level quantum systems by adopting the Bloch-vector representation. We identify a novel class of critical scenarios in which the so-called energy-level and decay-width vectors, ${\bf E}$ and ${\bfΓ}$, are orthogonal to one another, and the parameter $r = |{\bf Γ}|/(2|{\bf E}|)$ is less than~1. Most remarkably, we find that critical unstable qubit systems exhibit atypical behaviours like coherence--decoherence oscillations when analysed in an appropriately defined co-decaying frame of the system. By making use of a Fourier series decomposition, we define anharmonicity observables that quantify the degree of non-sinusoidal oscillation of a CUQ. We apply the results of our formalism to the neutral-meson systems and derive generic upper limits on these new observables. In particular, we provide a compilation table of all well-explored meson--antimeson two-level systems in terms of Bloch-sphere parameters.

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