2026-07-27 大阪公立大学
図：測定下の量子多体系と原子検出回数の概念図（Image: Issei Takahashi）
＜関連情報＞
- https://www.omu.ac.jp/info/research_news/entry-25211.html
- https://journals.aps.org/prl/abstract/10.1103/wv5b-r6sb
ポストセレクションフリー多体ダイナミクスにおける測定誘起量子ジャンプ統計のクロスオーバー Measurement-Induced Crossover of Quantum Jump Statistics in Postselection-Free Many-Body Dynamics
Kazuki Yamamoto and Ryusuke Hamazaki
Physical Review Letters Published: 23 July, 2026
DOI: https://doi.org/10.1103/wv5b-r6sb
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 ∝ following Poissonian statistics for sufficiently weak measurement strength, anomalous yet universal scaling law ∝ (∼2.7 up to =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.
