Mixed-state long-range order and criticality from measurement and feedback

• URL: http://arxiv.org/abs/2303.15507v2
• Date: Wed, 13 Sep 2023 23:45:03 GMT
• Title: Mixed-state long-range order and criticality from measurement and feedback
• Authors: Tsung-Cheng Lu, Zhehao Zhang, Sagar Vijay, Timothy H. Hsieh
• Abstract summary: We propose a general framework for using local measurements, local unitaries, and non-local classical communication to construct quantum channels. We present two applications using fermion occupation number measurement to convert spinful free fermions in one dimension into a quantum-critical mixed state. The latter is an example where mixed-state quantum criticality can emerge from a gapped state of matter in constant depth using local quantum operations and non-local classical communication.
• Score: 1.1142354615369277
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We propose a general framework for using local measurements, local unitaries, and non-local classical communication to construct quantum channels which can efficiently prepare mixed states with long-range quantum order or quantum criticality. As an illustration, symmetry-protected topological (SPT) phases can be universally converted into mixed-states with long-range entanglement, which can undergo phase transitions with quantum critical correlations of local operators and a logarithmic scaling of the entanglement negativity, despite coexisting with volume-law entropy. Within the same framework, we present two applications using fermion occupation number measurement to convert (i) spinful free fermions in one dimension into a quantum-critical mixed state with enhanced algebraic correlations between spins and (ii) Chern insulators into a mixed state with critical quantum correlations in the bulk. The latter is an example where mixed-state quantum criticality can emerge from a gapped state of matter in constant depth using local quantum operations and non-local classical communication.

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