2,751 research outputs found
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
Thermal Light as a Mixture of Sets of Pulses: the Quasi-1D Example
The relationship between thermal light and coherent pulses is of fundamental
and practical interest. We now know that thermal light cannot be represented as
a statistical mixture of single pulses. In this paper we ask whether or not
thermal light can be represented as a statistical mixture of sets of pulses. We
consider thermal light in a one-dimensional wave-guide, and find a convex
decomposition into products of orthonormal coherent states of localized,
nonmonochromatic modes.Comment: 6 pages and 3 figures, published versio
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
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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