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Ladewig, B., Diehl, S. and Buchhold, M. (2022). Monitored open fermion dynamics: Exploring the interplay of measurement, decoherence, and free Hamiltonian evolution. Phys. Rev. Res., 4 (3). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2643-1564

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Abstract

The interplay of unitary evolution and local measurements in many-body systems gives rise to a stochastic state evolution and to measurement-induced phase transitions in the pure state entanglement. In realistic settings, however, this dynamics may be spoiled by decoherence, e.g., dephasing, due to coupling to an environment or measurement imperfections. We investigate the impact of dephasing and the inevitable evolution into a non-Gaussian, mixed state, on the dynamics of monitored fermions. We approach it from three complementary perspectives: (i) the exact solution of the conditional master equation for small systems, (ii) quantum trajectory simulations of Gaussian states for large systems, and (iii) a renormalization group analysis of a bosonic replica field theory. For weak dephasing, constant monitoring preserves a weakly mixed state, which displays a robust measurement-induced phase transition between a critical and a pinned phase, as in the decoherence-free case. At strong dephasing, we observe the emergence of a new scale describing an effective temperature, which is accompanied with an increased mixedness of the fermion density matrix. Remarkably, observables such as density-density correlation functions or the subsystem parity still display scale invariant behavior even in this strongly mixed phase. We interpret this as a signature of gapless, classical diffusion, which is stabilized by the balanced interplay of Hamiltonian dynamics, measurements, and decoherence.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Ladewig, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Diehl, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Buchhold, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-659965
DOI:	10.1103/PhysRevResearch.4.033001
Journal or Publication Title:	Phys. Rev. Res.
Volume:	4
Number:	3
Date:	2022
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	2643-1564
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language QUANTUM-SYSTEMS; PROPAGATION; ENTROPY; DRIVEN; MODEL Multiple languages Physics, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/65996