2025/03/04 by Kazuki Yamamoto, Anonymous, Ryusuke Hamazaki +2 · 2 citations
Physics and Astronomy · #Spectroscopy and Quantum Chemical Studies #Cold Atom Physics and Bose-Einstein Condensates #Quantum many-body systems
paper · pdf · doi:10.1103/wv5b-r6sb
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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mo>∝</a:mo> <a:mi>L</a:mi> </a:mrow> </a:math> following Poissonian statistics for sufficiently weak measurement strength, anomalous yet universal scaling law <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mo>∝</c:mo> <c:msup> <c:mrow> <c:mi>L</c:mi> </c:mrow> <c:mrow> <c:mi>α</c:mi> </c:mrow> </c:msup> </c:mrow> </c:math> ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mrow> <e:mi>α</e:mi> <e:mo>∼</e:mo> <e:mn>2.7</e:mn> </e:mrow> </e:math> up to <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>L</g:mi> <g:mo>=</g:mo> <g:mn>20</g:mn> </g:math> ) 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.