Measurement-induced transition in U(1) monitored quantum circuits

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• Utkarsh Agrawal (UMass Amherst)
• Thursday 04 November 2021, 13:15-14:30
• https://bham-ac-uk.zoom.us/j/8268225040.

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

The “scrambling” of quantum information under unitary evolution into non-local degrees of freedom has emerged as a fundamental ingredient in the understanding of quantum thermalization, chaos, and spreading of errors in quantum computations. The robustness of this scrambling to external interference has been studied by subjecting the system to random projective measurements which compete to pause the dynamics of the information. Interestingly, a measurement-induced phase transition characterized by the unitary evolution’s ability/inability to entangle different parts of the system is observed as the function of the rate of the measurements. The phases are characterized by having volume law entanglement or area law entanglement.

In this talk, I will start by giving a overview of the key motivation and results in the field. I will then move on to quantum circuits with U(1) symmetry which, by Noether’s theorem, has a conserved charge. I will argue that the symmetry puts constraints on the flow of information by having a new type of phase transition inside the volume law, where the fluctuation of global charge goes from being non-zero to zero. This transition is marked by the ability of the measurements to efficiently identify the global charge of the system. We call this a “charge sharpening” transition.

This talk is part of the Theoretical Physics Seminars series.

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• Bham Talks
• Theoretical Physics Seminars
• What's on in Physics?
• https://bham-ac-uk.zoom.us/j/8268225040

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