Browsing by Author "Chen, J. F."

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Quantum teleportation of photonic qudits using linear optics
    (APS, 2019-09) Zhang, Chenyu; Chen, J. F.; Cui, Chaohan; Dowling, Jonathan P.; Ou, Z. Y.; Byrnes, Tim; Physics, School of Science
    One of the challenges of photon-based quantum teleportation is that both a source of entangled photons and an entangled basis measurement are required. For qubits, one can perform a probabilistic entangled basis measurement using linear optics, making the scheme efficient. However, for photonic qudits, an equivalent scheme remains difficult to devise. In this paper, we generalize the probabilistic photonic qubit teleportation protocol to qudits. The method relies on producing permutation entangled states nondeterministically which are superpositions of permutations of the spatial and qudit states of the photons. Our scheme nondeterministically teleports a photonic qudit using only entangled photon sources, linear optics, and photon detectors, and should be experimentally realizable for small qudit dimensions.
  • Thumbnail Image
    Item
    Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles
    (APS, 2016-07) Qian, Peng; Gu, Zhenjie; Cao, Rong; Wen, Rong; Ou, Z. Y.; Chen, J. F.; Zhang, Weiping; Department of Physics, School of Science
    The temporal purity of single photons is crucial to the indistinguishability of independent photon sources for the fundamental study of the quantum nature of light and the development of photonic technologies. Currently, the technique for single photons heralded from time-frequency entangled biphotons created in nonlinear crystals does not guarantee the temporal-quantum purity, except using spectral filtering. Nevertheless, an entirely different situation is anticipated for narrow-band biphotons with a coherence time far longer than the time resolution of a single-photon detector. Here we demonstrate temporally pure single photons with a coherence time of 100 ns, directly heralded from the time-frequency entangled biphotons generated by spontaneous four-wave mixing in cold atomic ensembles, without any supplemented filters or cavities. A near-perfect purity and indistinguishability are both verified through Hong-Ou-Mandel quantum interference using single photons from two independent cold atomic ensembles. The time-frequency entanglement provides a route to manipulate the pure temporal state of the single-photon source.