University of Birmingham > Talks@bham > Theoretical Physics Seminars > Measurement induced phase transition in a monitored fermion chain

Measurement induced phase transition in a monitored fermion chain

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

Recently, a new class of phase transitions has been discovered, which result from a competition between deterministic Hamiltonian dynamics, and stochastic dynamics imprinted by local measurements. The transition surfaces in the dynamics of entanglement, and a transition from volume to area law was found in random circuit models. Here we establish a novel entanglement transition scenario between a regime of logarithmic entanglement growth, and a quantum Zeno regime obeying an area law, in continuously monitored fermion dynamics. Beyond the entanglement signatures, also correlation functions which are non-linear in the quantum state witness the transition. It interpolates between a gapless phase with algebraically decaying correlation functions, and a gapped one with exponential behavior. This motivates a statistical mechanics style approach to the problem, interpolating between the microscopic measurement dynamics and the macroscopic correlators. While the unread measurement dynamics heats up to infinity, the non-linear state evolution hosts degrees of freedom captured by a non-hermitean quantum Sine-Gordon model. This gives both a physical picture for the phase transition in terms of a depinning from the measurement operator eigenstates induced by unitary dynamics, and places it into the BKT universality class.

This talk is part of the Theoretical Physics Seminars series.

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