Observer driven phase transitions: measurements, feedback, and universality in open quantum many body systems.
Abstract
APPROVED FOR PUBLIC RELEASE This proposal theoretically explores non-equilibrium entanglement transitions that are driven by locally measuring (and in some cases controlling) quantum many-body systems at a finite rate. Recent breakthroughs in the dynamics of monitored quantum systems have revealed a novel non-equilibrium phase transition in the entanglement of the many-body wavefunction between highly entangled and unentangled states by increasing the rate of local measurements. This transition arises due to the competition between entangling unitary dynamics and unentangling local projective measurements. At the measurement induced phase transition (MIPT), a Lorentz symmetry emerges with universal entanglement dynamics. This proposal seeks to develop a fundamental understanding of the universality classes of the MIPT and how they can be dramatically modified by incorporating feedback from the measurements to control the dynamics, both of which have implications for quantum computing in noisy intermediate scale quantum technologies, quantum error correction, quantum information, and fundamental questions in non-equilibrium quantum statistical mechanics. The specific objectives of this proposal are to: (i) Use a non-Pisot quasiperiodic measurement profile to show how the MIPT flows to a new universality class described by an infinite quasiperiodic fixed point. (ii) Determine how the field theory describing the MIPT in stabilizer circuits flows to the generic quantum limit in the presence of a dilute set of arbitrary gates. (iii) Study the universal properties of several examples of control induced phase transitions in a wide variety of quantum, classical, and semiclassical systems. Our proposed research utilizes a cross fertilization of ideas from statistical physics, critical phenomena, quantum information, and computational physics. The non-unitary time evolution of random quantum circuit models with measurements (and feedback) will be simulated numerically using a variety of techniques including quantum circuit simulations, the development of #near Clifford# simulations with measurements, and tensor networks. The successful completion of this proposal will transform our understanding of observer driven non-equilibrium entanglement transitions that are driven by local measurements or feedback. In (i),we will use non-Pisot quasiperiodic measurement profiles to access a novel class of infinite quasiperiodic fixed points that lie in between the known MIPT and its random static limit. The calculations in (ii) will allow us to identify the connection between the field theories governing percolation and the MIPT in various limits in order to understand the meaning of relevant perturbations to stabilizer circuits. Last, the investigations in (iii) will uncover the interplay of control and feedback on quantum dynamics. We expect to discover several distinct universality classes of control induced phase transitions in classical and quantum systems that canbe observed experimentally without the need for post selection.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 12, 2023
- Source ID
- N000142312357
Entities
People
- Jedediah H Pixley
Organizations
- Office of Naval Research
- Rutgers University
- United States Navy