The rise and fall of mixed-state entanglement: measurement, feedback, and decoherence

          @misc{ pirsa_PIRSA:24050030,
            doi = {10.48660/24050030},
            url = {https://pirsa.org/24050030},
            author = {Lu, Peter},
            keywords = {Quantum Information},
            language = {en},
            title = {The rise and fall of mixed-state entanglement: measurement, feedback, and decoherence},
            publisher = {Perimeter Institute},
            year = {2024},
            month = {may},
            note = {PIRSA:24050030 see, \url{https://pirsa.org}}
          }
          

Abstract

Long-range entangled mixed states are exotic many-body systems that exhibit intrinsically quantum phenomena despite extensive classical fluctuations. In the first part of the talk, I will show how they can be efficiently prepared with measurements and unitary feedback conditioned on the measurement outcome. For example, symmetry-protected topological phases can be universally converted into mixed states with long-range entanglement, and certain gapped topological states such as Chern insulators can be converted into mixed states with critical correlations in the bulk. In the second part of the talk, I will discuss how decoherence can drive interesting mixed-state entanglement transitions. By focusing on the toric codes in various space dimensions subject to certain types of decoherence, I will present the exact results of entanglement negativity, from which the universality class of entanglement transitions can be completely characterized.