Back-Action-Evading Measurements and Quantum Non-Demolition Variables via Linear Systems Engineering

• URL: http://arxiv.org/abs/2603.11507v1
• Date: Thu, 12 Mar 2026 03:49:18 GMT
• Title: Back-Action-Evading Measurements and Quantum Non-Demolition Variables via Linear Systems Engineering
• Abstract summary: We establish a framework for realizing back-action-evading (BAE) measurements and quantum non-demolition (QND) variables in linear quantum systems.<n>The key condition, a purely imaginary Hamiltonian with a real or imaginary coupling operator, enables BAE measurements of conjugate observables.
• Score: 4.647000119314947
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We establish a framework for realizing back-action-evading (BAE) measurements and quantum non-demolition (QND) variables in linear quantum systems. The key condition, a purely imaginary Hamiltonian with a real or imaginary coupling operator, enables BAE measurements of conjugate observables. Symmetric coupling further yields QND variables. For non-compliant systems, coherent feedback can engineer BAE measurements. Crucially, the QND interaction condition simultaneously ensures BAE measurements and promotes the coupling operator to a QND observable. This work provides a unified structural theory for enhancing precision in quantum metrology and sensing.

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