87 research outputs found
Using time reversal symmetry for sensitive incoherent matter-wave Sagnac interferometry
We present a theory of the transmission of incoherent guided matter-waves
through Sagnac interferometers. Interferometer configurations with only one
input and one output port have a property similar to the phase rigidity
observed in the transmission through Aharonov-Bohm interferometers in coherent
mesoscopic electronics. This property is connected to the existence of
counterpropagating paths of equal length and enables the operation of such
matter-wave interferometers with incoherent sources. High finesse
interferometers of this kind have a rotation sensitivity inversely proportional
to the square root of the finesse
The Faraday Quantum Clock and Non-local Photon Pair Correlations
We study the use of the Faraday effect as a quantum clock for measuring
traversal times of evanescent photons through magneto-refractive structures.
The Faraday effect acts both as a phase-shifter and as a filter for circular
polarizations. Only measurements based on the Faraday phase-shift properties
are relevant to the traversal time measurements. The Faraday polarization
filtering may cause the loss of non-local (Einstein-Podolsky-Rosen) two-photon
correlations, but this loss can be avoided without sacrificing the clock
accuracy. We show that a mechanism of destructive interference between
consecutive paths is responsible for superluminal traversal times measured by
the clock.Comment: 6 figure
Dynamic Matter-Wave Pulse Shaping
In this paper we discuss possibilities to manipulate a matter-wave with
time-dependent potentials. Assuming a specific setup on an atom chip, we
explore how one can focus, accelerate, reflect, and stop an atomic wave packet,
with, for example, electric fields from an array of electrodes. We also utilize
this method to initiate coherent splitting. Special emphasis is put on the
robustness of the control schemes. We begin with the wave packet of a single
atom, and extend this to a BEC, in the Gross-Pitaevskii picture. In analogy to
laser pulse shaping with its wide variety of applications, we expect this work
to form the base for additional time-dependent potentials eventually leading to
matter-wave pulse shaping with numerous application
Coupling between internal spin dynamics and external degrees of freedom in the presence of colored noise
We observe asymmetric transition rates between Zeeman levels (spin-flips) of
magnetically trapped atoms. The asymmetry strongly depends on the spectral
shape of an applied noise. This effect follows from the interplay between the
internal states of the atoms and their external degrees of freedom, where
different trapped levels experience different potentials. Such insight may
prove useful for controlling atomic states by the introduction of noise, as
well as provide a better understanding of the effect of noise on the coherent
operation of quantum systems.Comment: 5 pages, 4 figures; accepted to PR
Motion of a condensate in a shaken and vibrating harmonic trap
The dynamics of a Bose-Einstein condensate (BEC) in a time-dependent harmonic
trapping potential is determined for arbitrary variations of the position of
the center of the trap and its frequencies. The dynamics of the BEC wavepacket
is soliton-like. The motion of the center of the wavepacket, and the spatially
and temporally dependent phase (which affects the coherence properties of the
BEC) multiplying the soliton-like part of the wavepacket, are analytically
determined.Comment: Accepted for publication in J. Phys. B: At Mol Opt Phy
One-mirror Fabry-Perot and one-slit Young interferometry
We describe a new and distinctive interferometry in which a probe particle
scatters off a superposition of locations of a single free target particle. In
one dimension, probe particles incident on superposed locations of a single
"mirror" can interfere as if in a Fabry-Perot interferometer; in two
dimensions, probe particles scattering off superposed locations of a single
"slit" can interfere as if in a two-slit Young interferometer. The condition
for interference is loss of orthogonality of the target states and reduces, in
simple examples, to transfer of orthogonality from target to probe states. We
analyze experimental parameters and conditions necessary for interference to be
observed.Comment: 5 pages, 2 figures, RevTeX, submitted to PR
Organized Current Patterns in Disordered Conductors
We present a general theory of current deviations in straight current
carrying wires with random imperfections, which quantitatively explains the
recent observations of organized patterns of magnetic field corrugations above
micron-scale evaporated wires. These patterns originate from the most efficient
electron scattering by Fourier components of the wire imperfections with
wavefronts along the direction. We show that long range
effects of surface or bulk corrugations are suppressed for narrow wires or
wires having an electrically anisotropic resistivity
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