||渡辺 悠樹 准教授
||Charge fluctuation and charge-resolved entanglement in monitored quantum circuit with U(1) symmetry
||Recent attention has focused on the fact that critical phenomena can also occur in far-from-equilibrium systems, which share some properties of those in equilibrium systems. A pioneering example of those is the measurement-induced phase transition, stemming from the competition between the scrambling effect of the unitary dynamics and the disentangling effect of measurements[1,2]. Such phase transition occurs in a stochastic monitored system, and shows a conformal field theory (CFT)-like criticality as is the case in equilibrium critical systems . We numerically investigate this phase transition in terms of charge fluctuation in a subsystem and charge-resolved entanglement under U(1) symmetry associated with the total spin, or total particle number. We find that the late-time charge fluctuation exhibits logarithmic scaling at the transition and that the decay exponent of the two-point charge correlator is 2 for half-filling systems, which implies a free boson CFT, or a Tomonaga-Luttinger-liquid (TLL)-like universality. Furthermore, we compute the charge-resolved moment and find the results are well consistent with the TLL prediction, which supports the TLL-like universality of the measurement-induced phase transition under U(1) symmetry.
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