“Decoherence and Weak Measurement of Quantum Many-Body Systems: Chern Insulators and Quantum Criticality”
Under the effects of decoherence and weak measurement, pure-state wavefunctions are transformed into mixed-state density matrices. The universal physics of mixed states largely depends on the symmetries of the density matrix, which come in two forms: strong symmetry, preserved by each state in the ensemble, and weak symmetry, preserved only by the ensemble as a whole.
We demonstrate that Chern insulators exhibit instabilities under decoherence and weak measurement, unlike interactions, that explicitly break strong symmetries down to their weak versions. The resulting mixed states that Chern insulators are driven to by these effects are analogous to other familiar non-trivial topological states. Additionally, we will discuss the effects of decoherence and weak measurement on quantum critical states, including novel decoherence induced by reservoirs of anyons where weak dual symmetry plays a principal role.
Host: Meng Cheng