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arXiv · 1608.00766

Towards the Fundamental Quantum Limit of Linear Measurements of Classical Signals

Haixing Miao·Rana X Adhikari·Yiqiu Ma·Belinda Pang·Yanbei Chen
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Abstract

The quantum Cramér-Rao bound (QCRB) sets a fundamental limit for the measurement of classical signals with detectors operating in the quantum regime. Using linear-response theory and the Heisenberg uncertainty relation, we derive a general condition for achieving such a fundamental limit. When applied to classical displacement measurements with a test mass, this condition leads to an explicit connection between the QCRB and the Standard Quantum Limit which arises from a tradeoff between the measurement imprecision and quantum backaction; the QCRB can be viewed as an outcome of a quantum non-demolition measurement with the backaction evaded. Additionally, we show that the test mass is more a resource for improving measurement sensitivity than a victim of the quantum backaction, which suggests a new approach to enhancing the sensitivity of a broad class of sensors. We illustrate these points with laser interferometric gravitational wave detectors.

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Haixing Miao, Rana X Adhikari, Yiqiu Ma, Belinda Pang, Yanbei Chen. 2017-06-02. Towards the Fundamental Quantum Limit of Linear Measurements of Classical Signals. https://doi.org/10.1103/physrevlett.119.050801

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