300 research outputs found
Small School District Consolidation in Texas: An Analysis of its Impact on Costs and Student Achievement
Overarching framework between Gaussian quantum discord and Gaussian quantum illumination
We cast the problem of illuminating an object in a noisy environment into a
communication protocol. A probe is sent into the environment, and the presence
or absence of the object constitutes a signal encoded on the probe. The probe
is then measured to decode the signal. We calculate the Holevo information and
bounds to the accessible information between the encoded and received signal
with two different Gaussian probes---an Einstein-Podolsky-Rosen (EPR) state and
a coherent state. We also evaluate the Gaussian discord consumed during the
encoding process with the EPR probe. We find that the Holevo quantum advantage,
defined as the difference between the Holevo information obtained from the EPR
and coherent state probes, is approximately equal to the discord consumed.
These quantities become exact in the typical illumination regime of low object
reflectivity and low probe energy. Hence we show that discord is the resource
responsible for the quantum advantage in Gaussian quantum illumination.Comment: 12 pages, 8 figure
Conditional quantum-state engineering using ancillary squeezed-vacuum states
We investigate an optical scheme to conditionally engineer quantum states
using a beam splitter, homodyne detection and a squeezed vacuum as an ancillar
state. This scheme is efficient in producing non-Gaussian quantum states such
as squeezed single photons and superpositions of coherent states (SCSs). We
show that a SCS with well defined parity and high fidelity can be generated
from a Fock state of , and conjecture that this can be generalized for
an arbitrary Fock state. We describe our experimental demonstration of this
scheme using coherent input states and measuring experimental fidelities that
are only achievable using quantum resources.Comment: 10 pages, 14 figures, use pdf version, high quality figures available
on reques
Quantum State Engineering with Continuous-Variable Post-Selection
We present a scheme to conditionally engineer an optical quantum system via
continuous-variable measurements. This scheme yields high-fidelity squeezed
single photon and superposition of coherent states, from input single and two
photon Fock states respectively. The input Fock state is interacted with an
ancilla squeezed vacuum state using a beam-splitter. We transform the quantum
system by post-selecting on the continuous-observable measurement outcome of
the ancilla state. We experimentally demonstrate the principles of this scheme
using displaced coherent states and measure experimentally fidelities that are
only achievable using quantum resources.Comment: 4 pages, 5 figures, publishe
Spatial mode storage in a gradient echo memory
Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate
for efficient quantum storage and for linear optical quantum computation with
time-bin multiplexing. In this paper we investigate the spatial multimode
properties of a lambda-GEM system. Using a high-speed triggered CCD, we
demonstrate the storage of complex spatial modes and images. We also present an
in-principle demonstration of spatial multiplexing by showing selective recall
of spatial elements of a stored spin wave. Using our measurements, we consider
the effect of diffusion within the atomic vapour and investigate its role in
spatial decoherence. Our measurements allow us to quantify the spatial
distortion due to both diffusion and inhomogeneous control field scattering and
compare these to theoretical models.Comment: 11 pages, 9 figure
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