5,324 research outputs found
Fast optimization of parametrized quantum optical circuits
Parametrized quantum optical circuits are a class of quantum circuits in
which the carriers of quantum information are photons and the gates are optical
transformations. Classically optimizing these circuits is challenging due to
the infinite dimensionality of the photon number vector space that is
associated to each optical mode. Truncating the space dimension is unavoidable,
and it can lead to incorrect results if the gates populate photon number states
beyond the cutoff. To tackle this issue, we present an algorithm that is orders
of magnitude faster than the current state of the art, to recursively compute
the exact matrix elements of Gaussian operators and their gradient with respect
to a parametrization. These operators, when augmented with a non-Gaussian
transformation such as the Kerr gate, achieve universal quantum computation.
Our approach brings two advantages: first, by computing the matrix elements of
Gaussian operators directly, we don't need to construct them by combining
several other operators; second, we can use any variant of the gradient descent
algorithm by plugging our gradients into an automatic differentiation framework
such as TensorFlow or PyTorch. Our results will find applications in quantum
optical hardware research, quantum machine learning, optical data processing,
device discovery and device design.Comment: 21 pages, 10 figure
Broadband pseudothermal states with tunable spectral coherence generated via nonlinear optics
It is well known that the reduced state of a two-mode squeezed vacuum state
is a thermal state---i.e. a state whose photon-number statistics obey a
geometric distribution. More exotic \emph{broadband} states can be realized as
the reduced state of two spectrally-entangled beams generated using nonlinear
optics. We show that these broadband "pseudothermal" states are tensor products
of states in spectral Schmidt modes, whose photon-number statistics obey a
geometric distribution. We study the spectral and temporal coherence properties
of these states and show that their spectral coherence can be tuned---from
perfect coherence to complete incoherence---by adjusting the pump spectral
width. In the limit of a cw pump, these states are tensor products of true
thermal states, but with different temperatures at each frequency. This could
be an interesting state of light for investigating the interplay between
spectral, temporal, and photon-number coherences.Comment: 6 pages main text, 1 full-page figure (12 pages total including
reference and appendices
Dispersive spherical optical model of neutron scattering from Al27 up to 250 MeV
A spherical optical model potential (OMP) containing a dispersive term is
used to fit the available experimental database of angular distribution and
total cross section data for n + Al27 covering the energy range 0.1- 250 MeV
using relativistic kinematics and a relativistic extension of the Schroedinger
equation. A dispersive OMP with parameters that show a smooth energy dependence
and energy independent geometry are determined from fits to the entire data
set. A very good overall agreement between experimental data and predictions is
achieved up to 150 MeV. Inclusion of nonlocality effects in the absorptive
volume potential allows to achieve an excellent agreement up to 250 MeV.Comment: 13 figures (11 eps and 2 jpg), 3 table
Self-calibrating tomography for multi-dimensional systems
We present a formalism for self-calibrating tomography of arbitrary
dimensional systems. Self-calibrating quantum state tomography was first
introduced in the context of qubits, and allows the reconstruction of the
density matrix of an unknown quantum state despite incomplete knowledge of the
unitary operations used to change the measurement basis. We show how this can
be generalized to qudits, i.e. d-level systems, and provide a specific example
for a V-type three-level atomic system whose transition dipole moments are not
known. We show that it is always possible to retrieve the unknown state and
process parameters, except for a set of zero measure in the state-parameter
space.Comment: Revised version. 9 pages, 3 figure
FINANCIAL CHARACTERISTICS OF REFRIGERATED FOOD PRODUCTS TRUCKING FIRMS IN THE U.S.
This study provides an overview of the financial characteristics of U. S. refrigerated food products trucking firms as a group and by regions. The analytical tools used for evaluating the financial assessment of the industry were several commonly used liquidity, profitability, and solvency ratios. One of the results reveals that the pre-tax income-to-gross revenue ratio, a measure of profitability, for the firms as a group averaged 0.01. This value means that one-cent of every dollar earned in services ("sales") was available to pay taxes and distribute profits.Agribusiness,
Non-Hermitian engineering for brighter broadband pseudothermal light
We show that non-Hermitian engineering can play a positive role in quantum
systems. This is in contrast to the widely accepted notion that optical losses
are a foe that must be eliminated or, at least, minimized. We take advantage of
the interplay between nonlinear interactions and loss to show that
spectral-loss engineering can relax phase-matching conditions, enabling
generation of broadband pseudothermal states at new frequencies. This opens the
door for utilizing the full potential of semiconductor materials that exhibit
giant nonlinearities but lack the necessary ingredients for achieving
quasi-phase matching. This in turn may pave the way for building on-chip
quantum light sources.Comment: 11 pages (6 pages main text); 4 figure
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