Author Affiliations
Abstract
1 National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
2 Center for Quantum Science and Technology, Jiangxi Normal University, Nanchang 330022, China
3 State Key Laboratory of Precision Spectroscopy, Joint Institute of Advanced Science and Technology, School of Physics and Electronic Science, East China Normal University, Shanghai 200062, China
4 Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
5 e-mail: jtjing@phy.ecnu.edu.cn
6 e-mail: lijian.zhang@nju.edu.cn
Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters. Similar to the estimation of a constant phase, there is a standard quantum limit for stochastic phase estimation, which can be obtained with the Mach–Zehnder interferometer and coherent input state. Recently, it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squeezed light. However, practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored. Here we propose a method utilizing the SU(1,1) interferometer and coherent input states to estimate a stochastic optical phase. As an example, we investigate the Ornstein–Uhlenback stochastic phase. We analyze the performance of this method for three key estimation problems: prediction, tracking, and smoothing. The results show significant reduction of the mean square error compared with the Mach–Zehnder interferometer under the same photon number flux inside the interferometers. In particular, we show that the method with the SU(1,1) interferometer can achieve fundamental quantum scaling, achieve stochastic Heisenberg scaling, and surpass the precision of the canonical measurement.
Photonics Research
2020, 8(10): 10001653
Author Affiliations
Abstract
Center for Quantum Science and Technology, Jiangxi Normal University, Nanchang 330022, China
In this Letter, a new fractional entangling transformation (FrET) is proposed, which is generated in the entangled state representation by a unitary operator exp{iθ(ab +a b)} where a(b) is the Bosonic annihilate operator. The operator is actually an entangled one in quantum optics and differs evidently from the separable operator, exp{iθ(a a+b b)}, of complex fractional Fourier transformation. The additivity property is proved by employing the entangled state representation and quantum mechanical version of the FrET. As an application, the FrET of a two-mode number state is derived directly by using the quantum version of the FrET, which is related to Hermite polynomials.
270.0270 Quantum optics 070.2575 Fractional Fourier transforms 
Chinese Optics Letters
2015, 13(3): 030801
Author Affiliations
Abstract
Using the thermal field dynamics theory to convert the thermal state into a "pure" state in doubled Fock space, we find that the average value of e^{fa+a} under squeezed thermal state (STS) is just the generating function of Legendre polynomials. Based on this remarkable result, the normalization and photon-number distributions of m-photon added (or subtracted) STSs are conviently obtained as the Legendre polynomials. This new concise method can be expanded to the entangled case.
270.0270 Quantum optics 270.5290 Photon statistics 
Chinese Optics Letters
2012, 10(8): 082701

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