25 research outputs found
Squeezed-light source for the superresolving microscopy
We propose a source of multimode squeezed light that can be used for the
superresolving microscopy beyond the standard quantum limit. This source is an
optical parametric amplifier with a properly chosen diaphragm on its output and
a Fourier lens. We demonstrate that such an arrangement produces squeezed
prolate spheroidal waves which are the eigen modes of the optical imaging
scheme used in microscopy. The degree of squeezing and the number of spatial
modes in illuminating light, necessary for the effective object field
reconstruction, are evaluatedComment: 6 pages, 1 figure, RevTeX4. Shortened version will appear in Optics
Letter
Interferometric sorting of temporal Hermite-Gauss modes via temporal Gouy phase
We propose a device consisting of Mach-Zehnder interferometers and
realizing sorting of first temporal Hermite-Gauss modes of light passing
though it by adjusting the accumulated temporal Gouy phase acquired by every
mode. This mode-order-dependent phase shift is achieved by a fractional Fourier
transform realized by a time lens in one of interferometer's arms. We consider
application of such a sorter with just two interferometers to sorting the
Schmidt modes of a photon pair generated in spontaneous parametric
downconversion and find the theoretical lower bond on the cross-talk
probability of 5.5%.Comment: 18 pages, 6 figure
Quantum limits of super-resolution in reconstruction of optical objects
We investigate analytically and numerically the role of quantum fluctuations
in reconstruction of optical objects from diffraction-limited images. Taking as
example of an input object two closely spaced Gaussian peaks we demonstrate
that one can improve the resolution in the reconstructed object over the
classical Rayleigh limit. We show that the ultimate quantum limit of resolution
in such reconstruction procedure is determined not by diffraction but by the
signal-to-noise ratio in the input object. We formulate a quantitative measure
of super-resolution in terms of the optical point-spread function of the
system.Comment: 23 pages, 7 figures. Submitted to Physical Review A e-mail:
[email protected]
Controlling induced coherence for quantum imaging
Induced coherence in parametric down-conversion between two coherently pumped
nonlinear crystals that share a common idler mode can be used as an imaging
technique. Based on the interference between the two signal modes of the
crystals, an image can be reconstructed. By obtaining an expression for the
interference pattern that is valid in both the low- and the high-gain regimes
of parametric down-conversion, we show how the coherence of the light emitted
by the two crystals can be controlled. With our comprehensive analysis we
provide deeper insight into recent discussions about the application of induced
coherence to imaging in different regimes. Moreover, we propose a scheme for
optimizing the visibility of the interference pattern so that it directly
corresponds to the degree of coherence of the light generated in the two
crystals. We find that this scheme leads in the high-gain regime to a
visibility arbitrarily close to unity.Comment: 9 pages, 4 figure
Making photons indistinguishable by a time lens
We propose an application of quantum temporal imaging to restoring the
indistinguishability of the signal and the idler photons produced in the
type-II spontaneous parametric down-conversion with a pulsed broadband pump. It
is known that in this case, the signal and the idler photons have different
spectral and temporal properties. This effect deteriorates their
indistinguishability and, respectively, the visibility of the Hong-Ou-Mandel
interference. We demonstrate that inserting a time lens in one arm of the
interferometer and choosing properly its magnification factor restores perfect
indistinguishability of the signal and the idler photons and provides 100%
visibility of the Hong-Ou-Mandel interference in the limit of high focal group
delay dispersion of the time lens.Comment: 14 pages, 7 figure
Measuring nonclassicality of bosonic field quantum states via operator ordering sensitivity
We introduce a new distance-based measure for the nonclassicality of the
states of a bosonic field, which outperforms the existing such measures in
several ways. We define for that purpose the operator ordering sensitivity of
the state which evaluates the sensitivity to operator ordering of the Renyi
entropy of its quasi-probabilities and which measures the oscillations in its
Wigner function. Through a sharp control on the operator ordering sensitivity
of classical states we obtain a precise geometric image of their location in
the density matrix space allowing us to introduce a distance-based measure of
nonclassicality. We analyse the link between this nonclassicality measure and a
recently introduced quantum macroscopicity measure, showing how the two notions
are distinct