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ABSTRACT: We present the first experimental observation of quantum fluctuation spectra in two coupled optical cavities with an injected squeezed vacuum light. The quadrature components of the reflected squeezed vacuum spectra are measured by phase-sensitive homodyne detector. The experimental results demonstrate coupled-resonator-induced transparency in the quantum regime, in which the electromagnetically-induced-transparency-like characteristic of the absorption and dispersion properties of the coupled optical cavities determines the line shape of the reflected quantum noise spectra.
Physical Review Letters 04/2011; 106(15):153602. · 7.37 Impact Factor
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ABSTRACT: We demonstrate the capability of continuous variable Gaussian states to communicate multipartite quantum information. A quantum teamwork protocol is presented according to which an arbitrary possibly entangled multimode state can be faithfully teleported between two teams each comprising many cooperative users. We prove that N-mode Gaussian weighted graph states exist for arbitrary N that enable unconditional quantum teamwork implementations for any arrangement of the teams. These perfect continuous variable maximally multipartite entangled resources are typical among pure Gaussian states and are unaffected by the entanglement frustration occurring in multiqubit states.
Physical Review Letters 08/2009; 103(7):070501. · 7.37 Impact Factor
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ABSTRACT: We experimentally prepare a new type of continuous variable genuine four-partite entangled states, the quantum correlation property of which is different from that of the four-mode GHZ and cluster states, and which has not any qubit counterpart to be proposed at present. In the criterion inequalities for the full inseparability of the genuine four-partite entangled states, the amplitude and phase quadrature correlation variances totally consisting of three-party combination from the four entangled modes are involved. The measured correlation variances among the quadratures of the prepared entangled states satisfy the sufficient requirements for the full inseparability. The type of entangled states has especially potential application in quantum information with continuous quantum variables.
03/2008;
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ABSTRACT: We propose a scheme for continuous-variable telecloning with phase-conjugate inputs (PCI). Two cases of PCI telecloning are considered. The first case is where PCI telecloning produces $M$ clones nonlocally and $M$ anticlones locally, or vice versa. This kind of PCI telecloning requires only one EPR (Einstein-Podolsky-Rosen) entangled, two-mode squeezed state as a resource for building the appropriate multi-mode, multipartite entangled state via linear optics. The other case is a PCI telecloning protocol in which both clones and anticlones are created nonlocally. Such a scheme requires two EPR entangled states for the generation of a suitable multipartite entangled state. As our schemes are reversible, optimal cloning fidelities are achieved in the limit of infinite squeezing. Comment: 7 pages, 4 figures, appear in Phys. Rev. A
01/2008;
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ABSTRACT: We propose a new scheme for realizing nonlocal nondegenerate optical parametric amplifier by means of genuine four-mode entanglement. The nondegenerate optical parametric amplifier is regarded as a unitary transformation from two input fields to two outputs. Two inputs and two outputs are located at the remote stations respectively. Employing off-line four-mode entanglement, homodyne detection, classical communication and local displacement, the nonlocal nondegenerate optical parametric amplifier can be achieved. This scheme can be implemented with a setup that is experimentally accessible at present. Comment: 3 pages, 1 figures, submitted to Phys. Rev. A
11/2007;
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ABSTRACT: We describe a continuous-variable scheme for simulating the Kitaev lattice model and for detecting statistics of abelian anyons. The corresponding quantum optical implementation is solely based upon Gaussian resource states and Gaussian operations, hence allowing for a highly efficient creation, manipulation, and detection of anyons. This approach extends our understanding of the control and application of anyons and it leads to the possibility for experimental proof-of-principle demonstrations of anyonic statistics using continuous-variable systems. Comment: 5 pages, 2 figures, appear in Phys. Rev. A
11/2007;
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ABSTRACT: The cluster states and Greenberger-Horne-Zeilinger (GHZ) states are two different types of multipartite quantum entangled states. We present the first experimental results generating continuous variable quadripartite cluster and GHZ entangled states of electromagnetic fields. Utilizing two amplitude-quadrature and two phase-quadrature squeezed states of light and linearly optical transformations, the two types of entangled states for amplitude and phase quadratures of light are experimentally produced. The combinations of the measured quadrature variances prove the full inseparability of the generated four subsystems. The presented experimental schemes show that the multipartite entanglement of continuous variables can be deterministically generated with the relatively simple implementation.
Physical Review Letters 03/2007; 98(7):070502. · 7.37 Impact Factor
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ABSTRACT: The cluster states and Greenberger-Horne-Zeilinger (GHZ) states are two different types of multipartite quantum entangled states. We present the first experimental results generating continuous variable quadripartite cluster and GHZ entangled states of electromagnetic fields. Utilizing four two-mode squeezed states of light and linearly optical transformations, the two types of entangled states for amplitude and phase quadratures of light are experimentally produced. The combinations of the measured quadrature variances prove the full inseparability of the generated four subsystems. The presented experimental schemes show that the multipartite entanglement of continuous variables can be deterministically generated with the relatively simple implementation.
09/2006;
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ABSTRACT: We propose a new protocol of implementing continuous-variable quantum state transfer using partially disembodied transport. This protocol may improve the fidelity at the expense of the introduction of a semiquantum channel between the parties, in comparison with quantum teleportation using the same strength of entanglement. Depending on the amount of information destroyed in the measurement, this protocol may be regarded as a teleportation protocol (complete destruction of input state), or as a cloning protocol (partial destruction), or as a direct transmission (no destruction). This scheme can be straightforwardly implemented with a setup that is at present experimentally accessible.
Physical Review Letters 11/2005; 95(17):170501. · 7.37 Impact Factor
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ABSTRACT: We propose a scheme of continuous-variable reversible telecloning, which broadcast the information of an unknown state without loss from a sender to several spatially separated receivers exploiting multipartite entanglement as quantum channels. In this scheme, quantum information of an unknown state is distributed into $M$ optimal clones and $M-1$ anticlones using $2M$% -partite entanglement. For the perfect quantum information distribution that is optimal cloning, $2M$-partite entanglement is required to be a maximum two-party entanglement. Comparing with the quantum telecloning proposed by Loock and Braunstein [Phys. Rev. Lett. 87, 247901 (2001)], this protocol produces the anticlones (or time-reversed state) of the unknown quantum state, thus, keep all information of an unknown state. Comment: 5 pages, 2 figures
10/2005;
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ABSTRACT: Absorption and dispersion signals of D2 lines of rubidium atoms in a vapor cell have been experimentally investigated with the modulation transfer spectrum (MTS). Normal dispersion was observed at the transitions of Fg ? Fe = Fg - 1 and Fg ? Fe = Fg; anomalous dispersion, at transitions of Fg ?Fe = Fg + 1; and crossover resonance, by the transitions of Fg ?Fe = Fg - 1 and Fg ? Fe = Fg. The signal lineshape of the MTS and the detector phase are addressed accurately.
Optics Express 07/2003; 11(11):1338-44. · 3.59 Impact Factor
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ABSTRACT: A tripartite entangled state of bright optical field is experimentally produced using an Einstein-Podolsky-Rosen entangled state for continuous variables and linear optics. The controlled dense coding among a sender, a receiver, and a controller is demonstrated by exploiting the tripartite entanglement. The obtained three-mode "position" correlation and relative "momentum" correlation between the sender and the receiver, and thus the improvements of the measured signal to noise ratios of amplitude and phase signals with respect to the shot noise limit are 3.28 and 3.18 dB, respectively. If the mean photon number n equals 11 the channel capacity can be controllably inverted between 2.91 and 3.14. When n is larger than 1.0 and 10.52, the channel capacity of the controlled dense coding is predicted to exceed the ideal single channel capacity of coherent and squeezed state light communication, respectively.
Physical Review Letters 05/2003; 90(16):167903. · 7.37 Impact Factor
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ABSTRACT: The intensity-noise reduction of a laser-diode-pumped single-frequency ring Nd:YVO4 laser when different optoelectronic control systems are used is theoretically and experimentally investigated. It has been demonstrated that combining two techniques, optoelectronic feedback control of the drive current of the pump laser diode and feed-forward control of the output laser beam, is a good way to significantly suppress the intensity noise of a laser at low frequency.
Applied Optics 03/2003; 42(6):1068-74. · 1.41 Impact Factor
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ABSTRACT: Highly efficient quantum dense coding for continuous variables has been experimentally accomplished by means of exploiting a bright Einstein-Podolsky-Rosen (EPR) beam with anticorrelation of amplitude quadratures and correlation of phase quadratures. Two bits of classical information are encoded on two quadratures of a half of a bright EPR beam, then are simultaneously decoded by the other half of the EPR beam with the sensitivities beyond that of the shot noise limit. A high degree of immunity to unauthorized eavesdropping has been experimentally demonstrated.
Physical Review Letters 02/2002; 88(4):047904. · 7.37 Impact Factor
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ABSTRACT: Highly efficient quantum dense coding for continuous variables has been experimentally accomplished by means of exploiting bright EPR beam with anticorrelation of amplitude quadratures and correlation of phase quadratures, which is generated from a nondegenerate optical parametric amplifier operating in the state of deamplification. Two bits of classical information are encoded on two quadratures of a half of bright EPR beam at the sender Alice and transmitted to the receiver Bob via one qubit of the shared quantum state after encoding. The amplitude and phase signals are simultaneously decoded with the other half of EPR beam by the direct measurement of the Bell-state at Bob. The signal to noise ratios of the simultaneously measured amplitude and phase signals are improved 5.4dB and 4.8dB with respect to that of the shot noise limit respectively. A high degree of immunity to unauthorized eavesdropping of the presented quantum communication scheme is experimentally demonstrated. Comment: 11 pages, 5 figures
07/2001;
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ABSTRACT: The novel quantum teleportation and dense coding systems based on applying the amplitude-squeezed state light produced from the injection-locked laser diodes and a simple direct measurement scheme for the Bell state are proposed. 2001 Elsevier Science B.V. All rights reserved. In developing theoretical and experimental stud-ies of quantum information the quantum teleporta-tion which is the disembodied transport of an un-known quantum state from a sender to a remote re-ceiver [1] and the dense coding, in that the single bit sent from a sender to a receiver can successfully carry two bit of classical information [2], have attracted extensive interests. The nonlocal quantum entangle-ment plays a determinant role in the quantum infor-mation processing. Towards possible applications in quantum communication, both theoretical and exper-imental investigations increasingly focus on quantum states of continuous variable in an infinite-dimensional Hilbert space, since the EPR entangled state can be efficiently generated using squeezed light and beam splitters, for instance, the entangled EPR pairs re- (K. Peng).
Physics Letters A. 01/2001; 290:1-5.
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ABSTRACT: In this paper we present a scheme in which the amplitude-quadrature difference and phase-quadrature difference of two bright nonclassical beams serve as a pair of observed complementary variables that can be measured directly and can form a new squeezed state. Mixing such two quadrature-difference squeezed-state beams on a beam splitter produces characteristic of the Einstein-Podolsky-Rosen quantum entanglement. The experimental schemes producing such nonclassical beams and its possible applications in quantum information are discussed.
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Phys. Rev. A. 78(5):052121.
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ABSTRACT: We present a fully quantum model to process the intensity noise reduction of a single-frequency intracavity-doubled laser with an electronic feedback loop connected directly to the pump current of a laser diode. Adding an electronic feedback term to the quantum Langevin equations for a free-running single-frequency-doubling laser yields an analytical expression for the intensity noise spectrum of this system. Our previous experi-mental results with a Nd:YVO 4 /KTP green laser are basically in agreement with the theoretical calculation.
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ABSTRACT: We develop a scheme to reconstruct the optical quantum state of a single-mode bright light field by using the dispersion characteristics of the empty cavity. The input field has a strong coherent component at frequency 0 , which serves as a local oscillator (LO) to measure its two-sideband mode at 0 . We control the rela-tive phase of the 0–2 range between the LO and the two-sideband mode by scanning the cavity length, so the optical quantum state is tomographically reconstructed. In the proposed scheme the influence of the space-mode mismatch between the LO and measured mode on the quantum efficiency is eliminated, and this scheme can conveniently be used in some quantum optical systems in which LO field cannot be available. © 2000 Optical Society of America [S0740-3224(00)01510-1] OCIS code: 270.6570.
