222 research outputs found
Optical-fiber source of polarization-entangled photon pairs in the 1550nm telecom band
We present a fiber based source of polarization-entangled photon pairs that
is well suited for quantum communication applications in the 1550nm band of
standard fiber-optic telecommunications. Polarization entanglement is created
by pumping a nonlinear-fiber Sagnac interferometer with two time-delayed
orthogonally-polarized pump pulses and subsequently removing the time
distinguishability by passing the parametrically scattered signal-idler photon
pairs through a piece of birefringent fiber. Coincidence detection of the
signal-idler photons yields biphoton interference with visibility greater than
90%, while no interference is observed in direct detection of either the signal
or the idler photons. All four Bell states can be prepared with our setup and
we demonstrate violations of CHSH form of Bell's inequalities by up to 10
standard deviations of measurement uncertainty.Comment: 12 pages, 4 figures, to be submitted to Phys. Rev. Lett. See also
paper QTuB4 in QELS'03 Technical Digest (OSA, Washington, D.C., 2003). This
is a more complete versio
Coherent resonant interactions and slow light with molecules confined in photonic band-gap fibers
We investigate resonant nonlinear optical interactions and demonstrate
induced transparency in acetylene molecules in a hollow-core photonic band-gap
fiber at 1.5m. The induced spectral transmission window is used to
demonstrate slow-light effects, and we show that the observed broadening of the
spectral features is due to collisions of the molecules with the inner walls of
the fiber core. Our results illustrate that such fibers can be used to
facilitate strong coherent light-matter interactions even when the optical
response of the individual molecules is weak.Comment: 5 pages, 4 figure
Power Dependent Resonant Frequency of a Microwave Cavity due to Magnetic Levitation
Levitation of a magnet by superconductor has been an active area of research
to explore the quantum mechanical phenomenon. One of the techniques used is to
measure the levitation of a magnet placed inside the superconducting microwave
cavity. The levitation height can be probed by measuring the change in
microwave frequency. Here, we report measurements of the change in resonance
frequency of the microwave cavity with the Meissner-levitated permanent magnet.
The change in resonant frequency and quality factor was measured as a function
of input power and temperature. The change in resonate frequency is likely due
to the interaction of the magnet with the radio-frequency field inside the
microwave cavity
Gravitational Aharonov-Bohm Effect
We investigate the gravitational Aharonov-Bohm effect, by placing a quantum
system in free-fall around a gravitating body {\it e.g.} a satellite orbiting
the Earth. Since the system is in free-fall, by the equivalence principle, the
quantum system is locally in flat, gravity-free space-time - it is screened
from the gravitational field. For a slightly elliptical orbit, the
gravitational potential will change with time. This leads to the energy levels
of the quantum system developing side bands which is the signature for this
version of the Aharonov-Bohm effect. This contrasts with the normal signature
of the Aharonov-Bohm effect of shifting of interference fringes
Generation of different Bell states within the SPDC phase-matching bandwidth
We study the frequency-angular lineshape for a phase-matched nonlinear
process producing entangled states and show that there is a continuous variety
of maximally-entangled states generated for different mismatch values within
the natural bandwidth. Detailed considerations are made for two specific
methods of polarization entanglement preparation, based on type-II spontaneous
parametric down-conversion (SPDC) and on SPDC in two subsequent type-I crystals
producing orthogonally polarized photon pairs. It turns out that different Bell
states are produced at the center of the SPDC line and on its slopes,
corresponding to about half-maximum intensity level. These Bell states can be
filtered out by either frequency selection or angular selection, or both. Our
theoretical calculations are confirmed by a series of experiments, performed
for the two above-mentioned schemes of producing polarization-entangled photon
pairs and with two kinds of measurements: frequency-selective and
angular-selective.Comment: submitted for publicatio
Broadband stimulated four-wave parametric conversion on a tantalum pentoxide photonic chip
We exploit the large third order nonlinear susceptibility (?(3) or “Chi 3”) of tantalum pentoxide (Ta2O5) planar waveguides and realize broadband optical parametric conversion on-chip. We use a co-linear pump-probe configuration and observe stimulated four wave parametric conversion when seeding either in the visible or the infrared. Pumping at 800 nm we observe parametric conversion over a broad spectral range with the parametric idler output spanning from 1200 nm to 1600 nm in infrared wavelengths and from 555 nm to 600 nm in visible wavelengths. Our demonstration of on-chip stimulated four wave parametric conversion introduces Ta2O5 as a novel material for broadband integrated nonlinear photonic circuit applications
Energy level shift of quantum systems via the electric Aharonov-Bohm effect
A novel version of the electric Aharonov-Bohm effect is proposed where the
quantum system which picks up the Aharonov-Bohm phase is confined to a Faraday
cage with a time varying, spatially uniform scalar potential. The electric and
magnetic fields in this region are effectively zero for the entire period of
the experiment. The observable consequence of this version of the electric
Aharonov-Bohmn effect is to shift the energy levels of the quantum system
rather than shift the fringes of the 2-slit interference pattern. We show a
strong mathematical connection between this version of the scalar electric AB
effect and the AC Stark effect.Comment: 14 pages revtex, 4 figures. Added references and changes made to
address referee comments. To be published in PR
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