454 research outputs found
Ramsey interferometry with ultracold atoms
We examine the passage of ultracold two-level atoms through two separated
laser fields for the nonresonant case. We show that implications of the atomic
quantized motion change dramatically the behavior of the interference fringes
compared to the semiclassical description of this optical Ramsey
interferometer. Using two-channel recurrence relations we are able to express
the double-laser scattering amplitudes by means of the single-laser ones and to
give explicit analytical results. When considering slower and slower atoms, the
transmission probability of the system changes considerably from an
interference behavior to a regime where scattering resonances prevail. This may
be understood in terms of different families of trajectories that dominate the
overall transmission probability in the weak field or in the strong field
limit.Comment: 5 figures, 4 page
Comment on "Foundations of quantum mechanics: Connection with stochastic processes"
Recently, Olavo has proposed several derivations of the Schrodinger equation
from different sets of hypothesis ("axiomatizations") [Phys. Rev. A 61, 052109
(2000)]. One of them is based on the infinitesimal inverse Weyl transform of a
classically evolved phase space density. We show however that the Schrodinger
equation can only be obtained in that manner for linear or quadratic potential
functions.Comment: 3 pages, no figure
Quantum times of arrival for multiparticle states
Using the concept of crossing state and the formalism of second quantization,
we propose a prescription for computing the density of arrivals of particles
for multiparticle states, both in the free and the interacting case. The
densities thus computed are positive, covariant in time for time independent
hamiltonians, normalized to the total number of arrivals, and related to the
flux. We investigate the behaviour of this prescriptions for bosons and
fermions, finding boson enhancement and fermion depletion of arrivals.Comment: 10 a4 pages, 5 inlined figure
A measurement-based approach to quantum arrival times
For a quantum-mechanically spread-out particle we investigate a method for
determining its arrival time at a specific location. The procedure is based on
the emission of a first photon from a two-level system moving into a
laser-illuminated region. The resulting temporal distribution is explicitly
calculated for the one-dimensional case and compared with axiomatically
proposed expressions. As a main result we show that by means of a deconvolution
one obtains the well known quantum mechanical probability flux of the particle
at the location as a limiting distribution.Comment: 11 pages, 4 figures, submitted to Phys. Rev.
Simultaneous arrival of information in absorbing wave guides
We demonstrate that the temporal peak generated by specific electromagnetic
pulses may arrive at different positions simultaneously in an absorbing wave
guide. The effect can be used for triggering several devices all at once at
unknown distances from the sender or generally to transmit information so that
it arrives at the same time to receivers at different, unknown locations. This
simultaneity cannot be realized by the standard transmission methods
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