Coherent Feedback Approach to Continuous Quantum Error Correction

Stanford University, Stanford CA

Investigators

Abstract

This project will pursue a program of theoretical research to further develop a novel approach to autonomous quantum error correction. It will build on recent results which analyzed circuit designs that exploit coherent feedback, to implement quantum memories based on simple quantum codes without any need for external timing or control logic. This approach has the potential to contribute new strategies for robust quantum information processing that make optimal use of physical resources. Previous work will be extended to design coherent feedback circuits that implement quantum memories based on more sophisticated quantum codes that can correct for arbitrary single-qubit errors, and to explore advanced concepts such as circuit compression to exploit the quantum-mechanical nature of coherent feedback signals. The work will substantially strengthen connections among the abstract theory of quantum error correction, circuit theory as it exists in electrical engineering, and quantum optics/nanophotonics. This research project will provide interdisciplinary training for at least one graduate student, who will be required both to learn coherent-feedback quantum control theory and to understand fundamental aspects of quantum error correction theory beyond the usual basic concepts. The research makes essential use of technical methods developed quite recently by mathematical control theorists and applies them to important questions in quantum information theory, building important new bridges between these subject areas in the process. Such projects provide excellent source material for concrete examples in classroom teaching, such as the PI's existing graduate courses in "Estimation and Control Methods for Applied Physics" and "Quantum Device Physics of Atomic and Semiconductor Systems." They also provide important points of contact with colleagues in engineering and applied mathematics, who may be quite familiar with control theory and its connections to circuit design but have never thought of the relevance of their work for quantum physics.