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arXiv · 2503.02418

Measurement-Induced Crossover of Quantum Jump Statistics in Postselection-Free Many-Body Dynamics

Kazuki Yamamoto·Ryusuke Hamazaki
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Abstract

We reveal a nontrivial crossover of subsystem fluctuations of quantum jumps in continuously monitored many-body systems, which have a trivial maximally mixed state as a steady-state density matrix. While the fluctuations exhibit the standard volume law $\propto L$ following Poissonian statistics for sufficiently weak measurement strength, anomalous yet universal scaling law $\propto L^\alpha \:(\alpha\sim 2.7$ up to $L=20)$ indicating super-Poissonian statistics appears for strong measurement strength. This drastically affects the precision of estimating the rate of quantum jumps: for strong (weak) measurement, the estimation uncertainty is enhanced (suppressed) as the system size increases. We demonstrate that the anomalous scaling of the subsystem fluctuation originates from an integrated many-body autocorrelation function and that the transient dynamics contributes to the scaling law rather than the Liouvillian gap. The measurement-induced crossover is accessed only from the postselection-free information obtained from the time and the position of quantum jumps and can be tested in ultracold atom experiments.

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Kazuki Yamamoto, Ryusuke Hamazaki. 2025-03-04. Measurement-Induced Crossover of Quantum Jump Statistics in Postselection-Free Many-Body Dynamics. https://doi.org/10.1103/wv5b-r6sb

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