Observing measurement-induced transitions using a novel mixed-state entanglement measure

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• Christian Carisch, ETH Zurich
• Thursday 06 July 2023, 13:15-14:30
• Theory Library.

If you have a question about this talk, please contact Dr Hannah Price.

Measurement in Quantum Mechanics is among the most fundamental and debated processes in modern physics. In theory, it can be described by the use of pure quantum trajectories in stochastic Schrödinger equations, or (averaged) master equations for the density matrix of mixed states. Whereas both descriptions lead to the same measurement statistics for linear observables, the highly non-linear entanglement along quantum trajectories reveals measurement-induced transitions (MITs) invisible to the steady-state density matrix. Moreover, in contrast to the pure state trajectories, there is no standard way to quantify the entanglement of a mixed state. Recently, we have introduced the novel observable of “configuration coherence”, a mixed-state entanglement measure for systems with a symmetry and corresponding fixed conserved charge. In my talk, I will discuss the configuration coherence and use it to demonstrate that entanglement in both the trajectories and master equation approaches reveals the MIT . Specifically, we apply the configuration coherence to both scenarios and find the same intermediate-time entanglement dynamics. Our finding suggests that the MIT is a manifestation of coherent-to-diffusive crossover in quantum random walks. Our result enables the investigation of the measurement-induced entanglement phase transition in the context of mixed states and sheds light on its physical origin.

This talk is part of the Theoretical Physics Seminars series.

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• Bham Talks
• Theoretical Physics Seminars
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