Browsing by Subject "quantum metrology"

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    Accessible precisions for estimating two conjugate parameters using Gaussian probes
    (American Physical Society, 2020-05) Assad, Syed M.; Li, Jiamin; Liu, Yuhong; Zhao, Ningbo; Zhao, Wen; Lam, Ping Koy; Ou, Z. Y.; Li, Xiaoying; Physics, School of Science
    We analyze the precision limits for a simultaneous estimation of a pair of conjugate parameters in a displacement channel using Gaussian probes. Having a set of squeezed states as an initial resource, we compute the Holevo Cramér-Rao bound to investigate the best achievable estimation precisions if only passive linear operations are allowed to be performed on the resource prior to probing the channel. The analysis reveals the optimal measurement scheme and allows us to quantify the best precision for one parameter when the precision of the second conjugate parameter is fixed. To estimate the conjugate parameter pair with equal precision, our analysis shows that the optimal probe is obtained by combining two squeezed states with orthogonal squeezing quadratures on a 50:50 beam splitter. If different importance is attached to each parameter, then the optimal mixing ratio is no longer 50:50. Instead, it follows a simple function of the available squeezing and the relative importance between the two parameters.
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    Quantum enhanced joint measurement of two conjugate observables with an SU(1, 1) interferometer
    (IEEE, 2017) Liu, Yuhong; Li, Jiamin; Huo, Nan; Li, Xiaoying; Ou, Z. Y.; Physics, School of Science
    We jointly measure the phase and amplitude modulation of an optical field with the newly developed SU(1,1) interferometer. We simultaneously achieve a signal-to-noise ratio improvement of 1.1 and 1 dB over the standard quantum limit in amplitude and phase measurement.