399 research outputs found
Quantum teleportation of a single-photon wave packet
A quantum teleportation scheme based on the EPR-pair entangled with respect
to the ``energy+time'' variables is proposed. Teleportation of the multimode
state of a single-photon wave packet is considered.Comment: 6 pages, no figure
Teleportation of the Relativistic Quantum Field
The process of teleportation of a completely unknown one-particle state of a
free relativistic quantum field is considered. In contrast to the
non-relativistic quantum mechanics, the teleportation of an unknown state of
the quantum field cannot be in principle described in terms of a measurement in
a tensor product of two Hilbert spaces to which the unknown state and the state
of the EPR-pair belong. The reason is of the existence of a cyclic (vacuum)
state common to both the unknown state and the EPR-pair. Due to the common
vacuum vector and the microcausality principle (commutation relations for the
field operators), the teleportation amplitude contains inevitably contributions
which are irrelevant to the teleportation process. Hence in the relativistic
theory the teleportation in the sense it is understood in the non-relativistic
quantum mechanics proves to be impossible because of the impossibility of the
realization of the appropriate measurement as a tensor product of the
measurements related to the individual subsystems so that one can only speak of
the amplitude of the propagation of the field as a whole.Comment: 11 page
Photon Frequency Entanglement Swapping
We propose a simple non-linear crystal based optical scheme for experimental
realization of the frequency entanglement swapping between the photons
belonging to two independent biphotons.Comment: 5 pages, 1 figure. Submitted to Phys.Lett.
Cross section of the processes , , , in the energy region 200 MeV 3 GeV
The cross section for different processes induced by annihilation,
in the kinematical limit
, is
calculated taking into account first order corrections to the amplitudes and
the corrections due to soft emitted photons, with energy in the center of mass of the colliding beams. The results
are given separately for charge--odd and charge--even terms in the final
channels and . In case of pions, form
factors are taken into account. The differential cross sections for the
processes: , , have been calculated and the
corresponding formula are given in the ultrarelativistic limit . For a quantitative evaluation of the
contribution of higher order of the perturbation theory, the production of
, including radiative corrections, is calculated in the approach of
the lepton structure functions. This allows to estimate the precision of the
obtained results as better than 0.5% outside the energy region corresponding to
narrow resonances. A method to integrate the cross section, avoiding the
difficulties which arise from singularities is also described.Comment: 25 pages 3 firgur
Status of the PICASSO Project
The Picasso project is a dark matter search experiment based on the
superheated droplet technique. Preliminary runs performed at the Picasso Lab in
Montreal have showed the suitability of this detection technique to the search
for weakly interacting cold dark matter particles. In July 2002, a new phase of
the project started. A batch of six 1-liter detectors with an active mass of
approximately 40g was installed in a gallery of the SNO observatory in Sudbury,
Ontario, Canada at a depth of 6,800 feet (2,070m). We give a status report on
the new experimental setup, data analysis, and preliminary limits on
spin-dependent neutralino interaction cross section.Comment: 3 pages, 2 figures. To appear in the Proceedings of the TAUP 2003
conference, 5-9 September, 2003, University of Washington, Seattle, US
Anomalous Neutrino Interaction, Muon g-2, and Atomic Parity Nonconservation
We propose a simple unified description of two recent precision measurements
which suggest new physics beyond the Standard Model of particle interactions,
i.e. the deviation of in deep inelastic neutrino-nucleon
scattering and that of the anomalous magnetic moment of the muon. Our proposal
is also consistent with a third precision measurement, i.e. that of parity
nonconservation in atomic Cesium, which agrees with the Standard Model.Comment: 9 pages, including 1 figure, latest muon g-2 information adde
Single-crossover dynamics: finite versus infinite populations
Populations evolving under the joint influence of recombination and
resampling (traditionally known as genetic drift) are investigated. First, we
summarise and adapt a deterministic approach, as valid for infinite
populations, which assumes continuous time and single crossover events. The
corresponding nonlinear system of differential equations permits a closed
solution, both in terms of the type frequencies and via linkage disequilibria
of all orders. To include stochastic effects, we then consider the
corresponding finite-population model, the Moran model with single crossovers,
and examine it both analytically and by means of simulations. Particular
emphasis is on the connection with the deterministic solution. If there is only
recombination and every pair of recombined offspring replaces their pair of
parents (i.e., there is no resampling), then the {\em expected} type
frequencies in the finite population, of arbitrary size, equal the type
frequencies in the infinite population. If resampling is included, the
stochastic process converges, in the infinite-population limit, to the
deterministic dynamics, which turns out to be a good approximation already for
populations of moderate size.Comment: 21 pages, 4 figure
Generation of maximum spin entanglement induced by cavity field in quantum-dot systems
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.
Approximating open quantum system dynamics in a controlled and efficient way: A microscopic approach to decoherence
We demonstrate that the dynamics of an open quantum system can be calculated
efficiently and with predefined error, provided a basis exists in which the
system-environment interactions are local and hence obey the Lieb-Robinson
bound. We show that this assumption can generally be made. Defining a dynamical
renormalization group transformation, we obtain an effective Hamiltonian for
the full system plus environment that comprises only those environmental
degrees of freedom that are within the effective light cone of the system. The
reduced system dynamics can therefore be simulated with a computational effort
that scales at most polynomially in the interaction time and the size of the
effective light cone. Our results hold for generic environments consisting of
either discrete or continuous degrees of freedom
Dark Energy and Neutrino CPT Violation
In this paper we study the dynamical CPT violation in the neutrino sector
induced by the dark energy of the Universe. Specifically we consider a dark
energy model where the dark energy scalar derivatively interacts with the
right-handed neutrinos. This type of derivative coupling leads to a
cosmological CPT violation during the evolution of the background field of the
dark energy. We calculate the induced CPT violation of left-handed neutrinos
and find the CPT violation produced in this way is consistent with the present
experimental limit and sensitive to the future neutrino oscillation
experiments, such as the neutrino factory.Comment: 10 pages, 2 figures. Typos corrected and references added. To be
published in EPJ
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