Unravelling the emergence of quantum jumps in a monitored qubit

• URL: http://arxiv.org/abs/2602.02672v1
• Date: Mon, 02 Feb 2026 19:00:10 GMT
• Title: Unravelling the emergence of quantum jumps in a monitored qubit
• Authors: Barkay Guttel, Danielle Gov, Noam Netzer, Uri Goldblatt, Sergey Hazanov, Lalit M. Joshi, Alessandro Romito, Yuval Gefen, Parveen Kumar, Kyrylo Snizhko, Fabien Lafont, Serge Rosenblum,
• Abstract summary: Quantum jumps are among the most striking consequences of observation in quantum mechanics.<n>We map measurement-induced transitions in a monitored superconducting qubit.<n>Results reveal that the interplay between coherent driving, measurement, and decoherence gives rise to a hierarchy of distinct dynamical phases.
• Score: 29.627676149627302
• License: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Abstract: Quantum jumps, the collapse of a quantum system upon measurement, are among the most striking consequences of observation in quantum mechanics. While recent experiments have revealed the continuous nature of individual jumps, the crossover from coherent dynamics to measurement-dominated behaviour has remained elusive. Here, we tune the measurement strength of a continuously monitored superconducting qubit, and observe that quantum jumps emerge not through a gradual crossover, but via a cascade of three distinct dynamical transitions. The first transition manifests as an exceptional point where coherent oscillations abruptly cease, giving way to jumps towards a stable eigenstate. The second transition marks the onset of dynamical state freezing, where the qubit's dwell time near the eigenstate diverges. A third threshold signals entry into the quantum Zeno regime, where stronger measurement paradoxically suppresses relaxation. Strikingly, we find that decoherence does not blur these transitions but rather fundamentally restructures the dynamical phase diagram, notably inverting their order. These results map measurement-induced transitions in a monitored qubit, revealing that the interplay between coherent driving, measurement, and decoherence gives rise to a hierarchy of distinct dynamical phases.

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