Browsing by Author "Zhang, Weiping"

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    Absolute sensitivity of phase measurement in an SU(1,1) type interferometer
    (OSA, 2018) Du, Wei; Jia, Jun; Chen, J. F.; Ou, Z. Y.; Zhang, Weiping; Physics, School of Science
    Absolute sensitivity is measured for the phase measurement in an SU(1,1) type interferometer, and the results are compared to that of a Mach–Zehnder interferometer operated under the condition of the same intra-interferometer intensity. The interferometer is phase locked to a point with the largest quantum noise cancellation, and a simulated phase modulation is added in one arm of the SU(1,1) interferometer. Both the signal and noise level are estimated at the same frequency range, and we obtained 3 dB improvement in sensitivity for the SU(1,1) interferometer over the Mach–Zehnder interferometer. Our results demonstrate a direct phase estimation and may pave the way for practical applications of a nonlinear interferometer.
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    Atom-Light Hybrid Interferometer
    (APS, 2015-07) Chen, Bing; Qiu, Shuying; Guo, Jinxian; Chen, L. Q.; Ou, Z. Y.; Zhang, Weiping; Department of Physics, School of Science
    A new type of hybrid atom-light interferometer is demonstrated with atomic Raman amplification processes replacing the beam splitting elements in a traditional interferometer. This nonconventional interferometer involves correlated optical and atomic waves in the two arms. The correlation between atoms and light developed with the Raman process makes this interferometer different from conventional interferometers with linear beam splitters. It is observed that the high-contrast interference fringes are sensitive to the optical phase via a path change as well as the atomic phase via a magnetic field change. This new atom-light correlated hybrid interferometer is a sensitive probe of the atomic internal state and should find wide applications in precision measurement and quantum control with atoms and photons.
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    Atom-light superposition oscillation and Ramsey-like atom-light interferometer
    (OSA, 2016-07) Qiu, Cheng; Chen, Shuying; Chen, L. Q.; Chen, Bing; Guo, Jinxian; Ou, Z. Y.; Zhang, Weiping; Department of Physics, School of Science
    Coherent wave splitting is crucial in interferometers. Normally, the waves after this splitting are of the same type. But recent progress in interactions between atom and light has led to the coherent conversion of photon to atomic excitation. This makes it possible to split an incoming light wave into a coherent superposition state of atom and light and paves the way for an interferometer made of different types of waves. Here we report on a Rabi-like coherent-superposition oscillation observed between an atom and light in a Raman process. We construct a new kind of hybrid interferometer based on the atom–light coherent superposition state. Interference fringes are observed in both the optical output intensity and atomic output in terms of the atomic spin wave strength when we scan either or both of the optical and atomic phases. Such a hybrid interferometer can be used to interrogate atomic states by optical detection and will find its applications in precision measurement and quantum control of atoms and light.
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    Effects of losses in the hybrid atom-light interferometer
    (OSA, 2016-08) Chen, Zhao-Dan; Yuan, Chun-Hua; Ma, Hong-Mei; Li, Dong; Chen, L. Q.; Ou, Z. Y.; Zhang, Weiping; Department of Physics, School of Science
    Collective atomic excitation can be realized by the Raman scattering. Such a photon-atom interface can form an SU(1,1)-typed atom-light hybrid interferometer, where the atomic Raman amplification processes take the place of the beam splitting elements in a traditional Mach-Zehnder interferometer. We numerically calculate the phase sensitivities and the signal-to-noise ratios (SNRs) of this interferometer with the method of homodyne detection and intensity detection, and give their differences of the optimal phase points to realize the best phase sensitivities and the maximal SNRs from these two detection methods. The difference of the effects of loss of light field and atomic decoherence on measure precision is analyzed.
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    Effects of tobacco on human gingival fibroblasts
    (2011) Zhang, Weiping; Windsor, L. Jack; Song, Fengyu; Kowolik, Michael J.; Lee, Chao-Hung; Subramaniam, Denise Rogers
    The negative heath consequences of smoking are widely recognized, but there are still about 20% of the people in United States using tobacco products. Cigarette smoke condensate (CSC), the particulate matter of cigarette smoke, is comprised of thousands of chemicals (e.g., nicotine). Secondary only to bacterial plaque, cigarette smoking is a major risk factor for periodontal disease. Human gingival fibroblasts (HGFs) are the main cellular component of periodontal connective tissues. During the development of periodontal disease, collagen degradation occurs. Collagen is the major extracellular matrix component of the gingiva. The major extracellular matrix degrading enzymes produced by the HGFs are the matrix metalloproteinases (MMPs). The MMPs are mainly modulated by the tissue inhibitors of metalloproteinases (TIMPs). In this dissertation, three studies aimed at understanding the effects of tobacco on human gingival fibroblasts and their mechanisms have been conducted: the effects of CSC on HGF-mediated collagen degradation; comparison of the effects of CSC on HGFs with that of nicotine; and the combined effects of CSC and bacteria on HGFs. The cell proliferation of HGFs decreased and cytotoxicity increased in HGFs treated with increasing concentrations of CSC. CSC increased the collagen degrading ability of the HGFs by altering the production and localization of MMPs and TIMPs. Nicotine is one of the major components and the most pharmacologically active agent in tobacco. The percentage of nicotine in the CSC was 2.4%. CSC (100 µg/ml) increased the collagen degrading ability of the HGFs by affecting membrane associated MMP-2, MMP-14, and TIMP-2, but the level of nicotine in the CSC may only play a limited role in this process. Porphyromonas gingivalis (P. gingivalis) is an opportunistic pathogen involved in periodontal disease. The combined effects of CSC and P. gingivalis supernatant increased HGF-mediated collagen degradation by destroying the balance between the MMPs and TIMPs at the protein and mRNA levels. This project demonstrated that tobacco (with or without P. gingivalis) increased HGF mediated collagen degradation, as seen in the periodontal disease, through altering the MMPs and TIMPs.
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    Extracting the phase information from atomic memory by intensity correlation measurement
    (OSA, 2015-04) Guo, Jinxian; Zhang, Kai; Chen, L. Q.; Yuan, Chun-Hua; Bian, Cheng-ling; Ou, Z. Y.; Zhang, Weiping; Department of Physics, School of Science
    We demonstrate experimentally controlled storage and retrieval of the optical phase information in a higher-order interference scheme based on Raman process in 87Rb atomic vapor cells. An interference pattern is observed in intensity correlation measurement between the write Stokes field and the delayed read Stokes field as the phase of the Raman write field is scanned. This result implies that the phase information of the Raman write field can be written into the atomic spin wave via Raman process in a high gain regime and subsequently read out via a spin-wave enhanced Raman process, thus achieving optical storage of phase information. This technique should find applications in optical phase image storage, holography and information processing.
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    Intramode-correlation-enhanced phase sensitivities in an SU(1,1) interferometer
    (APS, 2017-09) Gong, Qian-Kun; Li, Dong; Yuan, Chun-Hua; Ou, Z. Y.; Zhang, Weiping; Physics, School of Science
    We theoretically derive the lower and upper bounds of quantum Fisher information (QFI) of an SU(1,1) interferometer whatever the input state chosen. According to the QFI, the crucial resource for quantum enhancement is shown to be large intramode correlations indicated by the Mandel Q parameter. The subtraction of photons from the squeezed vacuum state has the effect of increasing the average photon number of the new field state, as well as the intramode correlations. For example, for a coherent state ⊗ a squeezed vacuum state with a given fixed input mean number of photons as the input, if p photons are subtracted from the squeezed-vacuum state before inputting the SU(1,1) interferometer, the phase sensitivities can be improved due to the intramode-correlation increment.
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    Non-Hermitian Magnon-Photon Interference in an Atomic Ensemble
    (APS, 2019-06) Wen, Rong; Zou, Chang-Ling; Zhu, Xinyu; Chen, Peng; Ou, Z. Y.; Chen, J. F.; Zhang, Weiping; Physics, School of Science
    The interference of photons in a lossy beam splitter (BS) exhibits anticoalescence, which is surprising for bosons. Such a non-Hermitian system involving open quantum dynamics is of particular interest for quantum information processing and metrology. The Hermiticity of photonic devices is generally fixed according to the material, but is controllable at the interface of photons and atomic systems. Here, we demonstrate a tunable non-Hermitian BS for the interference between traveling photonic and localized magnonic modes. The crossover from a Hermitian to a non-Hermitian magnon-photon BS is achieved by controlling the coherent and incoherent interaction mediated by the excited levels of atoms, which is reconfigurable via the detuning of a control laser. A correlated interference pattern between the photons and magnons is demonstrated by such a non-Hermitian BS. Our system has the potential to operate with photons and magnons at the single-quanta level, and it provides a versatile quantum interface for studying the non-Hermitian quantum physics and parity-time symmetry.
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    Quantum dense metrology by an SU(2)-in-SU(1,1) nested interferometer
    (American Institute of Physics, 2020-07-13) Du, Wei; Ou, Z. Y.; Chen, J. F.; Zhang, Weiping; Physics, School of Science
    With the help of quantum entanglement, quantum dense metrology (QDM) is a technique that can make joint estimates of two conjugate quantities such as phase and amplitude modulations of an optical field, with an accuracy beating the standard quantum limit simultaneously. SU(1,1) interferometers (SUIs) can realize QDM with detection loss tolerance but is limited in absolute sensitivity. Here, we present a QDM scheme with a linear or SU(2) interferometer nested inside an SUI. By using a degenerate SUI and controlling the phase angle of the phase-sensitive amplifiers in the SUI, we can achieve the optimum quantum enhancement in the measurement precision of an arbitrary mixture of phase and amplitude modulation.
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    SU(1,1)-type light-atom-correlated interferometer
    (APS, 2015-08) Ma, Hongmei; Li, Dong; Yuan, Chun-Hua; Chen, L. Q.; Ou, Z. Y.; Zhang, Weiping; Department of Physics, School of Science
    The quantum correlation of light and atomic collective excitation can be used to compose an SU(1,1)-type hybrid light-atom interferometer, where one arm in the optical SU(1,1) interferometer is replaced by the atomic collective excitation. The phase-sensing probes include not only the photon field but also the atomic collective excitation inside the interferometer. For a coherent squeezed state as the phase-sensing field, the phase sensitivity can approach the Heisenberg limit under the optimal conditions. We also study the effects of the loss of light field and the dephasing of atomic excitation on the phase sensitivity. This kind of active SU(1,1) interferometer can also be realized in other systems, such as circuit quantum electrodynamics in microwave systems, which provides a different method for basic measurement using the hybrid interferometers.