60,047 research outputs found
Polar codes and polar lattices for the Heegard-Berger problem
Explicit coding schemes are proposed to achieve the rate-distortion function of the Heegard-Berger problem using polar codes. Specifically, a nested polar code construction is employed to achieve the rate-distortion function for doublysymmetric binary sources when the side information may be absent. The nested structure contains two optimal polar codes for lossy source coding and channel coding, respectively. Moreover, a similar nested polar lattice construction is employed when the source and the side information are jointly Gaussian. The proposed polar lattice is constructed by nesting a quantization polar lattice and a capacity-achieving polar lattice for the additive white Gaussian noise channel
Trapped ion quantum computation with transverse phonon modes
We propose a scheme to implement quantum gates on any pair of trapped ions
immersed in a large linear crystal, using interaction mediated by the
transverse phonon modes. Compared with the conventional approaches based on the
longitudinal phonon modes, this scheme is much less sensitive to ion heating
and thermal motion outside of the Lamb-Dicke limit thanks to the stronger
confinement in the transverse direction. The cost for such a gain is only a
moderate increase of the laser power to achieve the same gate speed. We also
show how to realize arbitrary-speed quantum gates with transverse phonon modes
based on simple shaping of the laser pulses.Comment: 5 page
Spin Hall effects for cold atoms in a light induced gauge potential
We propose an experimental scheme to observe spin Hall effects with cold
atoms in a light induced gauge potential. Under an appropriate configuration,
the cold atoms moving in a spatially varying laser field experience an
effective spin-dependent gauge potential. Through numerical simulation, we
demonstrate that such a gauge field leads to observable spin Hall currents
under realistic conditions. We also discuss the quantum spin Hall state in an
optical lattice.Comment: 4 pages; The published versio
A simple encoding of a quantum circuit amplitude as a matrix permanent
A simple construction is presented which allows computing the transition
amplitude of a quantum circuit to be encoded as computing the permanent of a
matrix which is of size proportional to the number of quantum gates in the
circuit. This opens up some interesting classical monte-carlo algorithms for
approximating quantum circuits.Comment: 6 figure
Polarizabilities of the 87Sr Clock Transition
In this paper, we propose an in-depth review of the vector and tensor
polarizabilities of the two energy levels of the 87Sr clock transition whose
measurement was reported in [P. G. Westergaard et al., Phys. Rev. Lett. 106,
210801 (2011)]. We conduct a theoretical calculation that reproduces the
measured coefficients. In addition, we detail the experimental conditions used
for their measurement in two Sr optical lattice clocks, and exhibit the
quadratic behaviour of the vector and tensor shifts with the depth of the
trapping potential and evaluate their impact on the accuracy of the clock
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