Quantifying measurement-induced quantum-to-classical crossover using an
open-system entanglement measure
- URL: http://arxiv.org/abs/2304.02965v2
- Date: Thu, 30 Nov 2023 09:41:26 GMT
- Title: Quantifying measurement-induced quantum-to-classical crossover using an
open-system entanglement measure
- Authors: Christian Carisch, Alessandro Romito, Oded Zilberberg
- Abstract summary: We study the entanglement of a single particle under continuous measurements.
We find that the entanglement at intermediate time scales shows the same qualitative behavior as a function of the measurement strength.
- Score: 49.1574468325115
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: The evolution of a quantum system subject to measurements can be described by
stochastic quantum trajectories of pure states. Instead, the ensemble average
over trajectories is a mixed state evolving via a master equation. Both
descriptions lead to the same expectation values for linear observables.
Recently, there is growing interest in the average entanglement appearing
during quantum trajectories. The entanglement is a nonlinear observable that is
sensitive to so-called measurement-induced phase transitions, namely,
transitions from a system-size dependent phase to a quantum Zeno phase with
area-law entanglement. Intriguingly, the mixed steady-state description of
these systems is insensitive to this phase transition. Together with the
difficulty of quantifying the mixed state entanglement, this favors quantum
trajectories for the description of the quantum measurement process. Here, we
study the entanglement of a single particle under continuous measurements
(using the newly developed configuration coherence) in both the mixed state and
the quantum trajectories descriptions. In both descriptions, we find that the
entanglement at intermediate time scales shows the same qualitative behavior as
a function of the measurement strength. The entanglement engenders a notion of
coherence length, whose dependence on the measurement strength is explained by
a cascade of underdamped-to-overdamped transitions. This demonstrates that
measurement-induced entanglement dynamics can be captured by mixed states.
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