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

• URL: http://arxiv.org/abs/2604.24243v1
• Date: Mon, 27 Apr 2026 09:53:41 GMT
• Title: On Realization of 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 is designed to engineer BAE measurements. Crucially, the QND interaction condition simultaneously ensures BAE measurements and promotes the coupling operator to a QND observable.

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