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Yi-Fang Ren

Publications and source records attributed to Yi-Fang Ren.

7 recordsLinked to original sources
arXiv2025

Enhancement of non-Gaussianity and nonclassicality of pair coherent states with postselected von Neumann measurement

We investigate the effects of postselected von Neumann measurements on the nonclassical properties of pair coherent states (PCS). We calculated key quantum characteristics, such as squeezing, photon statistics, and entanglement between the two PCS modes. Our results demonstrate that postselected von Neumann measurements enhance both the non-Gaussianity and nonclassicality of PCS. These findings are validated by analyzing the scaled joint Wigner function across various system parameters. The theoretical optimization scheme offers an alternative approach for improving PCS-based quantum information efficiency and facilitates practical implementations in quantum technologies.

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arXiv2025

Single-photon-added coherent state based postselected weak measurement

We investigated precision measurements in a two-level system coupled to a single-photon-added coherent state (SPACS) under postselection measurement. We analyzed strategies for improving measurement precision, including parameter estimation and the signal-to-noise ratio (SNR) in postselected weak measurements using the photon statistics of SPACS as the meter. Our results demonstrate that SPACS-based postselected weak measurements can outperform conventional measurement schemes in terms of precision. Additionally, we explicitly introduced an alternative weak measurement method commonly applied in dispersive light-atom interactions. Our work offers a new way for addressing fundamental issues in quantum precision measurement based on photon statistics, and it provides a method for extracting the phase and phase shifts of radiation fields through the weak values of system observables.

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arXiv2025

Effects of driven atomic ensemble on the output spectrum and entanglement of optomechanical system

This paper considers an indirect driving model of a cavity QED system in which the left cavity wall consists of a large ensemble of two-level atoms driven by a classical laser field at a specific resonant frequency, inducing an effective drive for the optomechanical system. We investigate the effects of the atomic ensemble on the output intensity squeezing spectrum and the entanglement between the optical and mechanical modes. Our results show that both the coupling between the atomic ensemble and the cavity mode and the excitation level of the atomic ensemble significantly influences the output spectrum and the entanglement. The theoretical model presented in this paper provides deeper insight into the mechanisms governing correlations and squeezing spectra in conventional optomechanical systems.

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arXiv2025

Post-selected von Neumann Measurement with Superpositions of Orbital-Angular-Momentum Pointer States

We investigated an orbital angular momentum (OAM) pointer within the framework of von Neumann measurements and discovered its significant impact on optimizing superpositions of Gaussian and Laguerre-Gaussian (LG) states. Calculations of the quadrature squeezing, the second-order cross-correlation function, the Wigner function, and the signal-to-noise ratio (SNR) support our findings. Specifically, by carefully selecting the anomalous weak value and the coupling strength between the measured system and the pointer, we demonstrated that the initial Gaussian state transforms into a non-Gaussian state after postselection. This transition highlights the potential of OAM pointers in enhancing the performance of quantum systems by tailoring state properties for specific applications.

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arXiv2025

Stronger sum uncertainty relations for non-Hermitian operators

The uncertainty relations (URs) of two arbitrary Hermitian and non-Hermitian incompatible operators represented by the product of variances have been confirmed theoretically and experimentally in various physical systems. However, the lower bound of the product uncertainty inequality can be null even for two non-commuting operators, i.e., a trivial case. Therefore, for two incompatible operators over the measured system state, the associated URs regarding the sum of variances are valid in a state-dependent manner, and the lower bound is guaranteed to be nontrivial. Although the sum URs formulated for Hermitian and unitary operators have been affirmed, the general forms for arbitrary non-Hermitian operators have not yet been investigated. This study presents the sum URs for non-Hermitian operators acting on system states using an appropriate Hilbert-space metric. The compatible forms of our sum inequalities with the conventional quantum mechanics are also provided via the G-metric formalism. Concrete examples illustrate the validity of the proposed sum URs in both PT-symmetric and PT-broken phases. The developed methods and results can help give an in-depth understanding of the usefulness of G-metric formalism in non-Hermitian quantum mechanics and the sum URs of incompatible operators within.

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arXiv2024

Separating the wave and particle attributes of two entangled photons

Wave-particle duality is one of the most intriguing counterfactual concepts in quantum theory. In our common sense, the wave and particle properties of a quantum object are inseparable. However, the recent studies based on Quantum Cheshire Cat phenomena showed that separating the physical properties of a quantum object including wave and particle attributes from itself are possible in microscopic system described by two-state vector formalism. In this study, we put forward a feasible scheme to spatially separate the wave and particle attributes of two entangled photons by properly choosing the pre- and post-selection of path states. Our scheme also guarantees that the observation of wave and particle properties of the two entangled photons always obey the Bohr's complementarity principle.

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