Speaker: Matthew P.A.Fisher (UCSB)

Host: Zhicheng Yang

Time: 10:00-11:00 am, April 20, 2023, GMT+8

Venue: Zoom Meeting ID:963 5796 8034 Password: 125125 or Koushare platform (https://www.koushare.com/lives/room/660145)

Abstract:

When a quantum system is coupled to a dissipative environment an initially pure state becomes rapidly mixed as information is lost, and classical behavior invariably follows. Recently, another type of open system dynamics has been explored, when a quantum system is continuously "monitored"by an observer, making a sequence of measurements, and a pure quantum state remains pure. The resulting quantum trajectories constitute an ensemble of pure states,which can in the many-body context, have a rich entanglement structure, exhibiting measurement-induced phase transitions (MIPT) between volume law and area law entanglement, and between phases with or without symmetry breaking and/or topological order. For mixed initial density matrices,monitoring can lead to a plethora of purification transitions,and reveals underlying connections with quantum encoding. While the MIPT occurs generically in a number of different models, its verification can be challenging even on an error-corrected quantum computer, due to the so-called post-selection problem. I will briefly describe recent proposals to access experimentally measurement-induced phase transitions (MIPT) employing"decoding",including the prospects of employing the linear cross-entropy, without requiring any post-selection of quantum trajectories.

Source: School of Physics