arXiv subjects

Yazhi Niu

Publications and source records attributed to Yazhi Niu.

5 recordsLinked to original sources

arXiv2025

Postselected amplification and photon recycling applied to optical sensing of magnetic fields

We apply the combined technique of postselected amplification and photon-recycling to an optical setup of magnetic field precision measurement. We propose two recycling schemes and carry out analytic expressions for the amplified signal and measurement sensitivity. The results show significant improvement of performance over conventional measurement. The underlying reason is twofold. On one aspect, introducing the technique of recycling eliminates the shortcoming of data discarding in postselection, thus maintains similar noise level of conventional measurement (without postselection). On the other aspect, performing intentional postselection within the recycling framework, which was originally proposed in the context of gravitational wave detection, can amplify the signal. Thus, the measurement signal-to-noise ratio is enhanced.

quant-ph↗

arXiv2025

Optical phase estimation via homodyne measurement in the presence of saturation effect of photodetectors

For optical phase estimation via homodyne measurement, we generalize the theory from detector's linear to nonlinear response regime, which accounts for the presence of saturation effect. For optical coherent light, we carry out analytic expressions for detector's current and estimate precision. Using specific device parameters, we illustrate the improved estimation after accounting for the saturation effect.

quant-ph↗

arXiv2024

Postselected amplification applied to atomic magnetometers

We propose to embed the atomic magnetometer (AM) into an optical Mach-Zehnder interferometer (MZI). We analyze the effect of amplification of the Faraday rotation (FR) angle of the probe laser light, by properly postselecting the path-information state of the laser photons when passing through the MZI. In the presence of saturation of photo-detectors and existence of polarization cross talk in the polarizing-beam-splitter performance, the amplified FR angle in the postselected photons makes the scheme be able to outperform the conventional measurement (without postselection), being thus further enhancing the sensitivity of the nowadays state-of-the-art optical AM.

quant-ph↗

arXiv2023

Enhanced super-Heisenberg scaling precision by nonlinear coupling and postselection

In quantum precision metrology, the famous result of Heisenberg limit scaling as $1/N$ (with $N$ the number of probes) can be surpassed by considering nonlinear coupling measurement. In this work, we consider the most practice-relevant quadratic nonlinear coupling and show that the metrological precision can be enhanced from the $1/N^{\frac{3}{2}}$ super-Heisenberg scaling to $1/N^2$, by simply employing a pre- and post-selection (PPS) technique, but not using any expensive quantum resources such as quantum entangled state of probes.

quant-ph↗

arXiv2022

Quantum-coherence-free precision metrology by means of difference-signal amplification

The novel weak-value-amplification (WVA) scheme of precision metrology is deeply rooted in the quantum nature of destructive interference between the pre- and post-selection states. And, an alternative version, termed as joint WVA (JWVA), which employs the difference-signal from the post-selection accepted and rejected results, has been found possible to achieve even better sensitivity (two orders of magnitude higher) under some technical limitations (e.g. misalignment errors). In this work, after erasing the quantum coherence, we analyze the difference-signal amplification (DSA) technique, which serves as a classical counterpart of the JWVA, and show that similar amplification effect can be achieved. We obtain a simple expression for the amplified signal, carry out characterization of precision, and point out the optimal working regime. We also discuss how to implement the post-selection of a classical mixed state. The proposed classical DSA technique holds similar technical advantages of the JWVA and may find interesting applications in practice.

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