20,051 research outputs found
Electromagnetically Induced Transparency with Quantized Fields in Optocavity Mechanics
We report electromagnetically induced transparency using quantized fields in
optomechanical systems. The weak probe field is a narrow band squeezed field.
We present a homodyne detection of EIT in the output quantum field. We find
that the EIT dip exists even though the photon number in the squeezed vacuum is
at the single photon level. The EIT with quantized fields can be seen even at
temperatures of the order of 100 mK paving the way for using optomechanical
systems as memory elements.Comment: 6 pages, 5 figure
Effects of self-phase modulation on weak nonlinear optical quantum gates
A possible two-qubit gate for optical quantum computing is the parity gate
based on the weak Kerr effect. Two photonic qubits modulate the phase of a
coherent state, and a quadrature measurement of the coherent state reveals the
parity of the two qubits without destroying the photons. This can be used to
create so-called cluster states, a universal resource for quantum computing.
Here, the effect of self-phase modulation on the parity gate is studied,
introducing generating functions for the Wigner function of a modulated
coherent state. For materials with non-EIT-based Kerr nonlinearities, there is
typically a self-phase modulation that is half the magnitude of the cross-phase
modulation. Therefore, this effect cannot be ignored. It is shown that for a
large class of physical implementations of the phase modulation, the quadrature
measurement cannot distinguish between odd and even parity. Consequently, weak
nonlinear parity gates must be implemented with physical systems where the
self-phase modulation is negligable.Comment: 7 pages, 4 figure
Experimental generation of an optical field with arbitrary spatial coherence properties
We describe an experimental technique to generate a quasi-monochromatic field
with any arbitrary spatial coherence properties that can be described by the
cross-spectral density function, . This is done by using a
dynamic binary amplitude grating generated by a digital micromirror device
(DMD) to rapidly alternate between a set of coherent fields, creating an
incoherent mix of modes that represent the coherent mode decomposition of the
desired . This method was then demonstrated experimentally
by interfering two plane waves and then spatially varying the coherent between
these two modes such that the interference fringe visibility was shown to vary
spatially between the two beams in an arbitrary and prescribed way.Comment: 6 pages, 5 figur
Amplification of Angular Rotations Using Weak Measurements
We present a weak measurement protocol that permits a sensitive estimation of
angular rotations based on the concept of weak-value amplification. The shift
in the state of a pointer, in both angular position and the conjugate orbital
angular momentum bases, is used to estimate angular rotations. This is done by
an amplification of both the real and imaginary parts of the weak-value of a
polarization operator that has been coupled to the pointer, which is a spatial
mode, via a spin-orbit coupling. Our experiment demonstrates the first
realization of weak-value amplification in the azimuthal degree of freedom. We
have achieved effective amplification factors as large as 100, providing a
sensitivity that is on par with more complicated methods that employ quantum
states of light or extremely large values of orbital angular momentum.Comment: 5 pages, 3 figures, contains supplementary informatio
Quantum-secured imaging
We have built an imaging system that uses a photon's position or
time-of-flight information to image an object, while using the photon's
polarization for security. This ability allows us to obtain an image which is
secure against an attack in which the object being imaged intercepts and
resends the imaging photons with modified information. Popularly known as
"jamming," this type of attack is commonly directed at active imaging systems
such as radar. In order to jam our imaging system, the object must disturb the
delicate quantum state of the imaging photons, thus introducing statistical
errors that reveal its activity.Comment: 10 pages (double spaced), 5 figure
Quantum memory for non-stationary light fields based on controlled reversible inhomogeneous broadening
We propose a new method for efficient storage and recall of non-stationary
light fields, e.g. single photon time-bin qubits, in optically dense atomic
ensembles. Our approach to quantum memory is based on controlled, reversible,
inhomogeneous broadening. We briefly discuss experimental realizations of our
proposal.Comment: 4 page
Nonlinear envelope equation for broadband optical pulses in quadratic media
We derive a nonlinear envelope equation to describe the propagation of
broadband optical pulses in second order nonlinear materials. The equation is
first order in the propagation coordinate and is valid for arbitrarily wide
pulse bandwidth. Our approach goes beyond the usual coupled wave description of
phenomena and provides an accurate modelling of the evolution of
ultra-broadband pulses also when the separation into different coupled
frequency components is not possible or not profitable
Analytical model of brittle destruction based on hypothesis of scale similarity
The size distribution of dust particles in nuclear fusion devices is close to
the power function. A function of this kind can be the result of brittle
destruction. From the similarity assumption it follows that the size
distribution obeys the power law with the exponent between -4 and -1. The model
of destruction has much in common with the fractal theory. The power exponent
can be expressed in terms of the fractal dimension. Reasonable assumptions on
the shape of fragments concretize the power exponent, and vice versa possible
destruction laws can be inferred on the basis of measured size distributions.Comment: 10 pages, 3 figure
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