EQuAL Seminar: Zhehao Zhang

"Novel Mixed-state Quantum Order and Criticalities from Measurements and Adaptive Feedback"

Recent developments in quantum simulators enable us to study exotic phases of matter by utilizing mid-circuit measurements and targeted unitary evolution. In the first part of my talk, I will present a class of quantum channels based on measurements and unitary feedback that can produce quantum many-body mixed states with long-range order and criticalities coexisting with extensive entropy in constant depth. As an example, I will show how to convert 1d Z2 x Z2 symmetry protected topological states into mixed-states with long-range GHZ-type order. In the second part of my talk, I will focus on an adaptive protocol that converts 1d spinful free fermions into a critical mixed state with enhanced correlations. I will show the resulting mixed-state density matrix can be captured by a Euclidean path integral, offering deeper insights into the structure of that mixed state.