4,322 research outputs found
Capacity of nonlinear bosonic systems
We analyze the role of nonlinear Hamiltonians in bosonic channels.
We show that the information capacity as a function of the channel energy is
increased with respect to the corresponding linear case, although only when the
energy used for driving the nonlinearity is not considered as part of the
energetic cost and when dispersive effects are negligible.Comment: 6 pages, 3 figure
Processing and Transmission of Information
Contains research objectives and summary of research on three research projects and reports on two research projects.National Aeronautics and Space Administration (Grant NGL 22-009-013)National Science Foundation (Grant GK-41464)National Science Foundation (Grant GK-41098)Joint Services Electronics Program (Contract DAAB07-74-C-0630)National Science Foundation (Grant GK-37582
Growth, processing, and optical properties of epitaxial Er_2O_3 on silicon
Erbium-doped materials have been investigated for generating and amplifying light in low-power chip-scale optical networks on silicon, but several effects limit their performance in dense microphotonic applications. Stoichiometric ionic crystals are a potential alternative that achieve an Er^(3+) density 100× greater. We report the growth, processing, material characterization, and optical properties of single-crystal Er_2O_3 epitaxially grown on silicon. A peak Er^(3+) resonant absorption of 364 dB/cm at 1535nm with minimal background loss places a high limit on potential gain. Using high-quality microdisk resonators, we conduct thorough C/L-band radiative efficiency and lifetime measurements and observe strong upconverted luminescence near 550 and 670 nm
Structure of the Phase in Pure Two-Mode Gaussian States
The two-mode relative phase associated with Gaussian states plays an
important role in quantum information processes in optical, atomic and
electronic systems. In this work, the origin and structure of the two-mode
relative phase in pure Gaussian states is studied in terms of its dependences
on the quadratures of the modes. This is done by constructing local canonical
transformations to an associated two-mode squeezed state. The results are
illustrated by studying the time dependence of the phase under a nonlocal
unitary model evolution containing correlations between the modes. In a more
general context, this approach may allow the two-mode phase to be studied in
situations sensitive to different physical parameters within experimental
configurations relevant to quantum information processing tasks
Capacities of Quantum Channels for Massive Bosons and Fermions
We consider the capacity of classical information transfer for noiseless
quantum channels carrying a finite average number of massive bosons and
fermions. The maximum capacity is attained by transferring the Fock states
generated from the grand-canonical ensemble. Interestingly, the channel
capacity for a Bose gas indicates the onset of a Bose-Einstein condensation, by
changing its qualitative behavior at the criticality, while for a channel
carrying weakly attractive fermions, it exhibits the signatures of
Bardeen-Cooper-Schrieffer transition. We also show that for noninteracting
particles, fermions are better carriers of information than bosons.Comment: 4 pages, 3 eps figures, RevTeX4; v2: discussions added, small
changes, published versio
Distinguishing between optical coherent states with imperfect detection
Several proposed techniques for distinguishing between optical coherent
states are analyzed under a physically realistic model of photodetection.
Quantum error probabilities are derived for the Kennedy receiver, the Dolinar
receiver and the unitary rotation scheme proposed by Sasaki and Hirota for
sub-unity detector efficiency. Monte carlo simulations are performed to assess
the effects of detector dark counts, dead time, signal processing bandwidth and
phase noise in the communication channel. The feedback strategy employed by the
Dolinar receiver is found to achieve the Helstrom bound for sub-unity detection
efficiency and to provide robustness to these other detector imperfections
making it more attractive for laboratory implementation than previously
believed
Optical Propagation and Communication
Contains research objectives and summary of research on three research projects, and reports on three research projects.National Aeronautics and Space Administration (Grant NGL 22-009-013)National Science Foundation (Grant ENG74-00131-A01)National Science Foundation (Grant ENG74-03996-A01
Operational Theory of Homodyne Detection
We discuss a balanced homodyne detection scheme with imperfect detectors in
the framework of the operational approach to quantum measurement. We show that
a realistic homodyne measurement is described by a family of operational
observables that depends on the experimental setup, rather than a single field
quadrature operator. We find an explicit form of this family, which fully
characterizes the experimental device and is independent of a specific state of
the measured system. We also derive operational homodyne observables for the
setup with a random phase, which has been recently applied in an ultrafast
measurement of the photon statistics of a pulsed diode laser. The operational
formulation directly gives the relation between the detected noise and the
intrinsic quantum fluctuations of the measured field. We demonstrate this on
two examples: the operational uncertainty relation for the field quadratures,
and the homodyne detection of suppressed fluctuations in photon statistics.Comment: 7 pages, REVTe
Minimum-error discrimination between subsets of linearly dependent quantum states
A measurement strategy is developed for a new kind of hypothesis testing. It
assigns, with minimum probability of error, the state of a quantum system to
one or the other of two complementary subsets of a set of N given
non-orthogonal quantum states occurring with given a priori probabilities. A
general analytical solution is obtained for N states that are restricted to a
two-dimensional subspace of the Hilbert space of the system. The result for the
special case of three arbitrary but linearly dependent states is applied to a
variety of sets of three states that are symmetric and equally probable. It is
found that, in this case, the minimum error probability for distinguishing one
of the states from the other two is only about half as large as the minimum
error probability for distinguishing all three states individually.Comment: Representation improved and generalized, references added. Accepted
as a Rapid Communication in Phys. Rev.
Novel cloning machine with supplementary information
Probabilistic cloning was first proposed by Duan and Guo. Then Pati
established a novel cloning machine (NCM) for copying superposition of multiple
clones simultaneously. In this paper, we deal with the novel cloning machine
with supplementary information (NCMSI). For the case of cloning two states, we
demonstrate that the optimal efficiency of the NCMSI in which the original
party and the supplementary party can perform quantum communication equals that
achieved by a two-step cloning protocol wherein classical communication is only
allowed between the original and the supplementary parties. From this
equivalence it follows that NCMSI may increase the success probabilities for
copying. Also, an upper bound on the unambiguous discrimination of two
nonorthogonal pure product states is derived. Our investigation generalizes and
completes the results in the literature.Comment: 22 pages; the presentation is revised, and some typos are correcte
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