2,868 research outputs found

    Coherent analysis of quantum optical sideband modes

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    We demonstrate a device that allows for the coherent analysis of a pair of optical frequency sidebands in an arbitrary basis. We show that our device is quantum noise limited and hence applications for this scheme may be found in discrete and continuous variable optical quantum information experiments.Comment: 3 pages, 3 figures, submitted to Optics Letter

    Multiplexed communication over a high-speed quantum channel

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    In quantum information systems it is of particular interest to consider the best way in which to use the non-classical resources consumed by that system. Quantum communication protocols are integral to quantum information systems and are amongst the most promising near-term applications of quantum information science. Here we show that a multiplexed, digital quantum communications system supported by comb of vacuum squeezing has a greater channel capacity per photon than a source of broadband squeezing with the same analogue bandwidth. We report on the time-resolved, simultaneous observation of the first dozen teeth in a 2.4 GHz comb of vacuum squeezing produced by a sub-threshold OPO, as required for such a quantum communications channel. We also demonstrate multiplexed communication on that channel

    Components of optical qubits encoded in sideband modes

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    We describe a scheme for the encoding and manipulation of single photon qubits in optical sideband modes using standard optical elements. We propose and analyze the radio frequency half-wave plate, which may be used to make arbitrary rotations of a state in the frequency basis, and the frequency beamsplitter, which may be used to separate (or combine) photons of different frequencies into (from) different spatial modes

    Single-photon side bands

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    Single-photon states (and other non-Gaussian states) are typically studied in the time domain. In contrast, continuous-variable Gaussian states such as squeezed states are typically studied at side-band frequencies. Much of modern optical communication technology is also based on side-band techniques. Here we discuss what it means to produce single-photon states at side-band frequencies and propose techniques for producing and analyzing such states

    A highly efficient two level diamond based single photon source

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    An unexplored diamond defect centre which is found to emit stable single photons at a measured rate of 1.6 MHz at room temperature is reported. The novel centre, identified in chemical vapour deposition grown diamond crystals, exhibits a sharp zero phonon line at 734 nm with a full width at half maximum of ~ 4 nm. The photon statistics confirm the center is a single emitter and provides direct evidence of the first true two-level single quantum system in diamond.Comment: 3 pages, 4 figure

    Noiseless signal amplification using positive electro-optic feedforward

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    We propose an electro-optic feedforward scheme which can in principle produce perfect noiseless signal amplification (signal transfer coefficient of T s = 1). We demonstrate the scheme experimentally and report, for a signal gain of 13.4 dB, a signal transfer coefficient of T s = 0.88 which is limited mainly by detector efficiencies (92%). The result clearly exceeds the standard quantum limit, T s = 0.5, set by the high gain limit of a phase insensitive linear amplifier. We use the scheme to amplify a small signal carried by 35% amplitude squeezed light and demonstrate that, unlike the fragile squeezed input, the signal amplified output is robust to propagation losses

    Demonstration of the spatial separation of the entangled quantum side-bands of an optical field

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    Quantum optics experiments on "bright" beams typically probe correlations between side-band modes. However the extra degree of freedom represented by this dual mode picture is generally ignored. We demonstrate the experimental operation of a device which can be used to separate the quantum side-bands of an optical field. We use this device to explicitly demonstrate the quantum entanglement between the side-bands of a squeezed beam

    Generation of a frequency comb of squeezing in an optical parametric oscillator

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    The multimode operation of an optical parametric oscillator (OPO) operating below threshold is calculated. We predict that squeezing can be generated in a comb that is limited only by the phase matching bandwidth of the OPO. Effects of technical noise on the squeezing spectrum are investigated. It is shown that maximal squeezing can be obtained at high frequency even in the presence of seed laser noise and cavity length fluctuations. Furthermore the spectrum obtained by detuning the laser frequency off OPO cavity resonance is calculated

    Unconditional Continuous Variable Dense Coding

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    We investigate the conditions under which unconditional dense coding can be achieved using continuous variable entanglement. We consider the effect of entanglement impurity and detector efficiency and discuss experimental verification. We conclude that the requirements for a strong demonstration are not as stringent as previously thought and are within the reach of present technology
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