3,824 research outputs found
Entanglement may enhance the channel capacity in arbitrary dimensions
We consider explicitly two examples of d-dimensional quantum channels with
correlated noise and show that, in agreement with previous results on Pauli
qubit channels, there are situations where maximally entangled input states
achieve higher values of the output mutual information than product states. We
obtain a strong dependence of this effect on the nature of the noise
correlations as well as on the parity of the space dimension, and conjecture
that when entanglement gives an advantage in terms of mutual information,
maximally entangled states achieve the channel capacity.Comment: 12 pages, 3 figure
Cloning quantum entanglement in arbitrary dimensions
We have found a quantum cloning machine that optimally duplicates the
entanglement of a pair of -dimensional quantum systems. It maximizes the
entanglement of formation contained in the two copies of any
maximally-entangled input state, while preserving the separability of
unentangled input states. Moreover, it cannot increase the entanglement of
formation of all isotropic states. For large , the entanglement of formation
of each clone tends to one half the entanglement of the input state, which
corresponds to a classical behavior. Finally, we investigate a local
entanglement cloner, which yields entangled clones with one fourth the input
entanglement in the large- limit.Comment: 6 pages, 3 figure
Signal amplification in a qubit-resonator system
We study the dynamics of a qubit-resonator system, when the resonator is
driven by two signals. The interaction of the qubit with the high-amplitude
driving we consider in terms of the qubit dressed states. Interaction of the
dressed qubit with the second probing signal can essentially change the
amplitude of this signal. We calculate the transmission amplitude of the probe
signal through the resonator as a function of the qubit's energy and the
driving frequency detuning. The regions of increase and attenuation of the
transmitted signal are calculated and demonstrated graphically. We present the
influence of the signal parameters on the value of the amplification, and
discuss the values of the qubit-resonator system parameters for an optimal
amplification and attenuation of the weak probe signal.Comment: 7 pages, 8 figure
Soliton dual comb in crystalline microresonators
We present a novel compact dual-comb source based on a monolithic optical
crystalline MgF multi-resonator stack. The coherent soliton combs generated
in two microresonators of the stack with the repetition rate of 12.1 GHz and
difference of 1.62 MHz provided after heterodyning a 300 MHz wide
radio-frequency comb. Analogous system can be used for dual-comb spectroscopy,
coherent LIDAR applications and massively parallel optical communications.Comment: 5 pages, 5 figure
Current state and tendencies of development of mass electronic educational resources
The report considers the current trends of mass electronic educational resources and technologies. Analysis of existing foreign electronic educational resources, as well as the Russian experience of development in this sphere. Makes a number of conclusions about the prospects of introduction of mass electronic educational technologies on the Russian market.В докладе рассмотрены современные тенденции развития массовых электронных образовательных ресурсов и технологий. Проводится анализ существующих зарубежных электронных образовательных ресурсов, а также российского опыта развития в данной сфере. Делается ряд выводов о перспективности внедрения массовых электронных образовательных технологий на российском рынке
Extending Hudson's theorem to mixed quantum states
According to Hudson's theorem, any pure quantum state with a positive Wigner
function is necessarily a Gaussian state. Here, we make a step towards the
extension of this theorem to mixed quantum states by finding upper and lower
bounds on the degree of non-Gaussianity of states with positive Wigner
functions. The bounds are expressed in the form of parametric functions
relating the degree of non-Gaussianity of a state, its purity, and the purity
of the Gaussian state characterized by the same covariance matrix. Although our
bounds are not tight, they permit us to visualize the set of states with
positive Wigner functions.Comment: 4 pages, 2 figure
Entanglement enhanced classical capacity of quantum communication channels with correlated noise in arbitrary dimensions
We study the capacity of d-dimensional quantum channels with memory modeled
by correlated noise. We show that, in agreement with previous results on Pauli
qubit channels, there are situations where maximally entangled input states
achieve higher values of mutual information than product states. Moreover, a
strong dependence of this effect on the nature of the noise correlations as
well as on the parity of the space dimension is found. We conjecture that when
entanglement gives an advantage in terms of mutual information, maximally
entangled states saturate the channel capacity.Comment: 10 pages, 5 figure
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