Kunchi Peng

Shanxi University, Yangkü, Shanxi Sheng, China

Are you Kunchi Peng?

Claim your profile

Publications (102)247.88 Total impact

  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Single-mode squeezing and Fourier transformation operations are two essential logical gates in continuous-variable quantum computation, which have been experimentally implemented by means of an optical four-mode cluster state. In this paper, we present a simpler and more efficient protocol based on the use of Einstein-Podolsky-Rosen two-mode entangled states to realize the same operations. The theoretical calculations and the experimental results demonstrate that the presented scheme not only decreases the requirement to the resource quantum states at the largest extent but also enhances significantly the squeezing degree and the fidelity of the resultant modes under an identical resource condition. That is because in our system the influence of the excess noises deriving from the imperfect squeezing of the resource states is degraded. The gate operations applying two-mode entanglement can be utilized as a basic element in a future quantum computer involving a large-scale cluster state.
    03/2014;
  • [show abstract] [hide abstract]
    ABSTRACT: The optimal physical conditions of single-longitudinal-mode (SLM) operation for continuous-wave all-solid-state lasers with high output powers are investigated theoretically and experimentally. The dependence of the operation conditions on the linear and nonlinear intracavity losses of the laser is numerically calculated. The theoretical analysis is demonstrated by the experimental measurements on a home-made Nd:YVO<sub>4</sub> laser. The stable SLM output up to 33.7 W with optical-optical conversion efficiency of 44.9% at 1064 nm wavelength is recorded for over 7 h. The experimental results are in good agreement with the theoretical expectation.
    Optics Letters 03/2014; 39(5):1117-20. · 3.39 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Long-lived and high-fidelity memory for a photonic polarization qubit (PPQ) is crucial for constructing quantum networks. We present a millisecond storage system based on electromagnetically induced transparency, in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy and, thus, the PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of the polarization states are 98.6% at 200 μs and 78.4% at 4.5 ms, respectively.
    Physical Review Letters 12/2013; 111(24):240503. · 7.94 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Measurement-based one-way quantum computation using cluster states as resources provides an efficient model to perform computation and information processing of quantum codes. Arbitrary Gaussian quantum computation can be implemented sufficiently by long single-mode and two-mode gate sequences. However, continuous variable gate sequences have not been realized so far due to an absence of cluster states larger than four submodes. Here we present the first continuous variable gate sequence consisting of a single-mode squeezing gate and a two-mode controlled-phase gate based on a six-mode cluster state. The quantum property of this gate sequence is confirmed by the fidelities and the quantum entanglement of two output modes, which depend on both the squeezing and controlled-phase gates. The experiment demonstrates the feasibility of implementing Gaussian quantum computation by means of accessible gate sequences.
    Nature Communications 11/2013; 4:2828. · 10.02 Impact Factor
  • Wenzhe Wang, Huadong Lu, Jing Su, Kunchi Peng
    [show abstract] [hide abstract]
    ABSTRACT: We present a diode-pumped broadband tunable single-frequency and frequency-doubling Nd:YVO<sub>4</sub>/LBO laser with high output power of 10.5 W in all tuning ranges around 532 nm. An etalon placed inside the resonator and the laser gain medium in a wedge shape are used for the coarse- and fine-tuning elements, respectively. By independently scanning the temperatures of the two tuning elements, broadband tunable ranges of 12 and 24 GHz have been achieved, respectively, for the fundamental and the second-harmonic waves.
    Applied Optics 04/2013; 52(11):2279-85. · 1.69 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Entangled states of light including low-loss optical fiber transmission and atomic resonance frequencies are essential resources for future quantum information networks. We present the experimental achievement on the three-color entanglement generation at 852, 1550, and 1440 nm wavelengths for optical continuous variables. The entanglement generation system consists of two cascaded nondegenerated optical parametric oscillators (NOPOs). The flexible selectivity of nonlinear crystals in the two NOPOs and the tunable property of NOPO provide large freedom for the frequency selection of three entangled optical beams. The presented system will hopefully be developed as a practical entangled source to be used in quantum-information networks with atomic storage units and long fiber transmission lines.
    Physical Review Letters 12/2012; 109(25):253604. · 7.94 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The preparation of multipartite entangled states is the prerequisite for exploring quantum information networks and quantum computation. In this Letter, we present what we believe is the first experimental demonstration of an eight-partite spatially separated continuous variable (CV) cluster state of optical modes. Via the linearly optical transformation of eight squeezed states of light, the eight-partite cluster entangled state with amplitude and phase quadrature correlations are prepared. The generated eight entangled photonic qumodes are spatially separated, which provides valuable quantum resources for implementing CV quantum information protocols.
    Optics Letters 12/2012; 37(24):5178-80. · 3.39 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: The superactivation of multipartite bound entanglement (BE) is a special protocol proposed by Shor et al. in 2003, which can distill Einstein-Podolsky-Rosen (EPR) entanglement states between two subsystems of two multipartite BE states. Here we present the first experimental realization of the superactivation of the BE state, in which two copies of the four-partite unlockable BE state in a continuous-variable regime are used. Coupling two thermal states with Gaussian noises into two submodes of an EPR entangled state on two 50-50 beam splitters respectively, the four output optical modes form a four-partite unlocklable BE state. Using two EPR entangled states, we experimentally produce two BE states first. Then through a superactivation operation involving measurements and feedback on the two BE states, an EPR entangled state is distilled out between two designated parties of the two four-partite BE states. The experiment demonstrates the superadditivity of quantum entanglement as the individual BE state cannot be distilled, only two BE states together can be distilled.
    Physical Review Letters 05/2012; · 7.94 Impact Factor
  • Aihong Tan, Changde Xie, Kunchi Peng
    [show abstract] [hide abstract]
    ABSTRACT: We propose a generation system of continuous-variable (CV) three-color entangled state of bright optical beams based on two cascaded standard nondegenerate optical parametric oscillators (NOPOs) above the threshold. One of signal and idler beams produced by the first NOPO is used for the pump light of the second NOPO. The three-color entanglement among signal and idler beams produced by the second NOPO and the retained another beam of the first NOPO is theoretically demonstrated. The symplectic eigenvalues of the partial transposition covariance matrix of the generated optical entangled state are numerically calculated in terms of experimentally reachable system parameters. The optimal operation conditions of the cascaded NOPOs system for obtaining high entanglement are found. The calculated results explicitly demonstrate that the OPO action can transfer entanglement. Due to that the cavity parameters and the nonlinear crystals of the two NOPOs can be freely chosen, the flexibility of the proposed protocol is relatively good and the system can be also extended to prepare entangled states with more parts easily.
    Physical Review A 01/2012; 85(1). · 3.04 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We present a cascaded system consisting of three non-degenerate optical parametric amplifiers (NOPAs) for the generation and the enhancement of quantum entanglement of continuous variables. The entanglement of optical fields produced by the first NOPA is successively enhanced by the second and the third NOPAs from -5.3 $dB$ to -8.1 $dB$ below the quantum noise limit. The dependence of the enhanced entanglement on the physical parameters of the NOPAs and the reachable entanglement limitation for a given cascaded NOPA system are calculated. The calculation results are in good agreement with the experimental measurements.
    Physical Review A 01/2012; · 3.04 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Coherent feedback control (CFC) of multipartite optical entangled states produced by a non-degenerate optical parametric amplifier is theoretically studied. The features of the quantum correlations of amplitude and phase quadratures among more than two entangled optical modes can be controlled by tuning the transmissivity of the optical beam splitter in CFC loop. The physical conditions to enhance continuous variable multipartite entanglement of optical fields utilizing CFC loop are obtained. The numeric calculations based on feasible physical parameters of realistic systems provide direct references for the design of experimental devices.
    Physical Review A 01/2012; · 3.04 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: We experimentally demonstrate the cascaded entanglement enhancement of continuous variables. The quantum correlations are successively enhanced by two nondegenerate optical parametric amplifiers from -5.3 dB to -8.1 dB below quantum noise limit.
    Lasers and Electro-Optics (CLEO), 2012 Conference on; 01/2012
  • [show abstract] [hide abstract]
    ABSTRACT: A high-power single-frequency laser at 671 and 1342 nm is designed and built. We find that for a high power ${\rm Nd}{:}{\rm YVO}_{4}$ laser, the thermal load of gain medium at 1342 nm lasing is much more stronger than that without lasing, which results in a bistability-like phenomenon on the relation curve between the output power and pump power. Based on the consideration to this special phenomenon, in our design, the cavity parameters are optimized carefully to satisfy the laser stability condition for both cases before and after lasing, the thermal effect of the ${\rm Nd}{:}{\rm YVO}_{4}$ crystal is mitigated by increasing appropriately the fundamental mode size. The maximal output powers of 2.8 W at 671 nm and 850 mW at 1342 nm are simultaneously achieved.
    IEEE Journal of Quantum Electronics 01/2012; 48(1):67-72. · 1.83 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: In this paper, we present the first experimental demonstration on continuous variable quantum key distribution using determinant Einstein-Podolsky-Rosen entangled states of optical field. By means of the instantaneous measurements of the quantum fluctuations of optical modes respectively distributed at sender and receiver, the random bits of secret key are obtained without the need for signal modulation. The post-selection boundaries for the presented entanglement-based scheme against both Gaussian collective and individual attacks are theoretically concluded. The final secret key rates of 84 kbits/s and 3 kbits/s are completed under the collective attack for the transmission efficiency of 80% and 40%, respectively.
    EPL (Europhysics Letters) 09/2011; 87(2). · 2.26 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: A high-power single-frequency Nd:YAP/LBO laser with stable dual wavelength outputs is designed and built. The laser resonator satisfying optimal coupling condition for second-harmonic generation is in a configuration of a figure “8” shaped ring cavity consisting of two convex mirrors and two concave mirrors. An additional wedge YVO<sub>4</sub> crystal is inserted in the resonator to act as a polarizer, so that the stability of the laser operation is improved. The maximum output powers of 4.5 W at 540 nm and 1.5 W at 1080 nm are simultaneously achieved. The measured power stabilities of the fundamental wave and the second-harmonic wave are ±0.32% and ±0.6% for 3 h, respectively.
    IEEE Journal of Quantum Electronics 08/2011; · 1.83 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We experimentally demonstrate the manipulation of two-orthogonal components of a spin wave in an atomic ensemble. Based on Raman two-photon transition and Larmor spin precession induced by magnetic field pulses, the coherent rotations between the two components of the spin wave is controllably achieved. Successively, the two manipulated spin-wave components are mapped into two orthogonal polarized optical emissions, respectively. By measuring Ramsey fringes of the retrieved optical signals, the \pi/2-pulse fidelity of ~96% is obtained. The presented manipulation scheme can be used to build an arbitrary rotation for qubit operations in quantum information processing based on atomic ensembles.
    Physical Review A 07/2011; · 3.04 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Two schemes of Doppler-free high-resolution velocity-selective optical-pumping atomic spectroscopy, named single-resonance optical pumping (SROP) and double-resonance optical pumping (DROP), are performed and characterized with room-temperature cesium vapor cells. Due to velocity-selective optical pumping from one hyperfine fold of ground state to another via one-photon excitation in SROP or cascade two-photon excitation in DROP and decay processes thereafter, the atomic population variation of one hyperfine fold of ground state is indicated by SROP and DROP spectra by using of the transmission of the probe laser which is usually frequency locked to a cycling hyperfine transition. As a result, SROP and DROP spectra often have flat background and higher signal-to-noise ratio. Therefore, SROP and DROP spectra are very useful for measurement of the dressed-state splitting of ground state with an alkali atomic vapor cell, precise measurement of hyperfine splitting of alkali atomic excited states, frequency references for laser frequency stabilization, two-color MOT, and so on.
    Proc SPIE 05/2011;
  • Huadong Lu, Jing Su, Changde Xie, Kunchi Peng
    [show abstract] [hide abstract]
    ABSTRACT: Using a multi-longitudinal-mode (MLM) and a single-longitudinal-mode (SLM) all-solid-state green lasers to be the pumping sources of a continuous-wave Ti:sapphire laser, respectively, the intensity-noise dependence of the Ti:sapphire laser on the longitudinal-mode structure of pumping sources is experimentally studied. The comparison between the theoretical prediction based on the quantum-mechanical model and the experimental measurement for the intensity-noise spectra is presented.
    Optics Express 01/2011; 19(2):1344-53. · 3.55 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We present an experimental demonstration of dual-channel memory in a single tripod atomic system. The total readout signal exhibits either constructive or destructive interference when the dual-channel spin-wave excitations (SWEs) are retrieved by two reading beams with a controllable relative phase. When the two reading beams have opposite phases, the SWEs will remain in the medium, which can be retrieved later with two in-phase reading beams. Such a phase-sensitive storage and retrieval scheme can be used to measure and control the relative phase between the two SWEs in the memory medium, which may find applications in quantum-information processing.
    Physical Review A 01/2011; 83(4). · 3.04 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We experimentally demonstrated that the quantum correlations of amplitude and phase quadratures between signal and idler beams produced from a non-degenerate optical parametric amplifier (NOPA) can be significantly improved by using a mode cleaner in the pump field and reducing the phase fluctuations in phase locking systems. Based on the two technical improvements the quantum entanglement measured with a two-mode homodyne detector is enhanced from approximately 4 dB to approximately 6 dB below the quantum noise limit using the same NOPA and nonlinear crystal.
    Optics Express 03/2010; 18(6):6149-55. · 3.55 Impact Factor