945 research outputs found

    Generation of two-mode nonclassical states and a quantum phase gate operation in trapped ion cavity QED

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    We propose a scheme to generate nonclassical states of a quantum system, which is composed of the one-dimensional trapped ion motion and a single cavity field mode. We show that two-mode SU(2) Schr\"odinger-cat states, entangled coherent states, two-mode squeezed vacuum states and their superposition can be generated. If the vibration mode and the cavity mode are used to represent separately a qubit, a quantum phase gate can be implemented.Comment: to appear in PR

    Generation of arbitrary two dimensional motional state of a trapped ion

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    We present a scheme to generate an arbitrary two-dimensional quantum state of motion of a trapped ion. This proposal is based on a sequence of laser pulses, which are tuned appropriately to control transitions on the sidebands of two modes of vibration. Not more than (M+1)(N+1)(M+1)(N+1) laser pulses are needed to generate a pure state with upper phonon number MM and NN in the xx and yy direction respectively.Comment: to appear in PR

    Multipartite entangled coherent states

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    We propose a scheme for generating multipartite entangled coherent states via entanglement swapping, with an example of a physical realization in ion traps. Bipartite entanglement of these multipartite states is quantified by the concurrence. We also use the NN--tangle to compute multipartite entanglement for certain systems. Finally we establish that these results for entanglement can be applied to more general multipartite entangled nonorthogonal states.Comment: 7 pages, two figures. We added more detail discussions on the generation of multipartite entangled coherent states and multipartite entangelemen

    Underwater hearing in sea snakes (Hydrophiinae): first evidence of auditory evoked potential thresholds

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    The viviparous sea snakes (Hydrophiinae) are a secondarily aquatic radiation of more than 60 species that possess many phenotypic adaptations to marine life. However, virtually nothing is known of the role and sensitivity of hearing in sea snakes. This study investigated the hearing sensitivity of the fully marine sea snake Hydrophis stokesii by measuring auditory evoked potential (AEP) audiograms for two individuals. AEPs were recorded from 40 Hz (the lowest frequency tested) up to 600 Hz, with a peak in sensitivity identified at 60 Hz (163.5 dB re. 1 ”Pa or 123 dB re. 1 ”m s⁻ÂČ). Our data suggest that sea snakes are sensitive to low-frequency sounds but have relatively low sensitivity compared with bony fishes and marine turtles. Additional studies are required to understand the role of sound in sea snake life history and further assess these species' vulnerability to anthropogenic noise.Lucille Chapuis, Caroline C. Kerr, Shaun P. Collin, Nathan S. Hart and Kate L. Sander

    Quantum teleportation of entangled coherent states

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    We propose a simple scheme for the quantum teleportation of both bipartite and multipartite entangled coherent states with the successful probability 1/2. The scheme is based on only linear optical devices such as beam splitters and phase shifters, and two-mode photon number measurements. The quantum channels described by multipartite maximally entangled coherent states are readily made by the beam splitters and phase shifters.Comment: 4 pages, no figure

    Multiorder coherent Raman scattering of a quantum probe field

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    We study the multiorder coherent Raman scattering of a quantum probe field in a far-off-resonance medium with a prepared coherence. Under the conditions of negligible dispersion and limited bandwidth, we derive a Bessel-function solution for the sideband field operators. We analytically and numerically calculate various quantum statistical characteristics of the sideband fields. We show that the multiorder coherent Raman process can replicate the statistical properties of a single-mode quantum probe field into a broad comb of generated Raman sidebands. We also study the mixing and modulation of photon statistical properties in the case of two-mode input. We show that the prepared Raman coherence and the medium length can be used as control parameters to switch a sideband field from one type of photon statistics to another type, or from a non-squeezed state to a squeezed state and vice versa.Comment: 12 pages, 7 figures, to be published in Phys. Rev.

    Generation of maximum spin entanglement induced by cavity field in quantum-dot systems

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    Equivalent-neighbor interactions of the conduction-band electron spins of quantum dots in the model of Imamoglu et al. [Phys. Rev. Lett. 83, 4204 (1999)] are analyzed. Analytical solution and its Schmidt decomposition are found and applied to evaluate how much the initially excited dots can be entangled to the remaining dots if all of them are initially disentangled. It is demonstrated that the perfect maximally entangled states (MES) can only be generated in the systems of up to 6 dots with a single dot initially excited. It is also shown that highly entangled states, approximating the MES with a good accuracy, can still be generated in systems of odd number of dots with almost half of them being excited. A sudden decrease of entanglement is observed by increasing the total number of dots in a system with a fixed number of excitations.Comment: 6 pages, 7 figures, to appear in Phys. Rev.
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