5,740 research outputs found
Classical capacity of the lossy bosonic channel: the exact solution
The classical capacity of the lossy bosonic channel is calculated exactly. It
is shown that its Holevo information is not superadditive, and that a
coherent-state encoding achieves capacity. The capacity of far-field,
free-space optical communications is given as an example.Comment: 4 pages, 2 figures (revised version
Analytical Blowup Solutions to the Pressureless Navier-Stokes-Poisson Equations with Density-dependent Viscosity in R^N
We study the N-dimensional pressureless Navier--Stokes-Poisson equations with
density-dependent viscosity. With the extension of the blowup solutions for the
Euler-Poisson equations, the analytical blowup solutions,in radial symmetry, in
R^N are constructed.Comment: 12 Pages, more detail in the introduction to explain the validity of
the mode
Cloning of Gaussian states by linear optics
We analyze in details a scheme for cloning of Gaussian states based on linear
optical components and homodyne detection recently demonstrated by U. L.
Andersen et al. [PRL 94 240503 (2005)]. The input-output fidelity is evaluated
for a generic (pure or mixed) Gaussian state taking into account the effect of
non-unit quantum efficiency and unbalanced mode-mixing. In addition, since in
most quantum information protocols the covariance matrix of the set of input
states is not perfectly known, we evaluate the average cloning fidelity for
classes of Gaussian states with the degree of squeezing and the number of
thermal photons being only partially known.Comment: 8 pages, 7 figure
School-based curriculum development as reflective practice: a case study in Hong Kong
This paper examines a school-based curriculum development (SBCD) experience in Hong Kong. Traditionally, curriculum change in Hong Kong has normally been bureaucratic with teachers’ actions monitored. This qualitative case study investigates the lived experience of an SBCD practice. Semi-structured interviews were utilized to examine teachers’ perceptions of the reflective SBCD experience in their school and what adaptations they had made when delivering the school-based materials. The findings identified that all teachers held a positive attitude towards this reflective approach to SBCD and emphasized artistry in their teaching practice. Teachers also exercised discretion in response to their students’ level and interests when implementing the school-based curriculum at the classroom level. This research concludes that a reflective approach to curriculum planning with a bottom-up implementation can empower teachers reflecting their creativity, artistry, knowledge of the subject and related pedagogy, and knowledge of their students. The findings of this case study thus contrast sharply with previous research relating to Hong Kong government-led SBCD programs which focus more on meeting the requirements of the intended curriculum than on personalizing the curriculum to meet to learners’ needs
Bosonic Memory Channels
We discuss a Bosonic channel model with memory effects. It relies on a
multi-mode squeezed (entangled) environment's state. The case of lossy Bosonic
channels is analyzed in detail. We show that in the absence of input energy
constraints the memory channels are equivalent to their memoryless
counterparts. In the case of input energy constraint we provide lower and upper
bounds for the memory channel capacity.Comment: 6 pages, 2 figure
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
On the Relationship between Resolution Enhancement and Multiphoton Absorption Rate in Quantum Lithography
The proposal of quantum lithography [Boto et al., Phys. Rev. Lett. 85, 2733
(2000)] is studied via a rigorous formalism. It is shown that, contrary to Boto
et al.'s heuristic claim, the multiphoton absorption rate of a ``NOON'' quantum
state is actually lower than that of a classical state with otherwise identical
parameters. The proof-of-concept experiment of quantum lithography [D'Angelo et
al., Phys. Rev. Lett. 87, 013602 (2001)] is also analyzed in terms of the
proposed formalism, and the experiment is shown to have a reduced multiphoton
absorption rate in order to emulate quantum lithography accurately. Finally,
quantum lithography by the use of a jointly Gaussian quantum state of light is
investigated, in order to illustrate the trade-off between resolution
enhancement and multiphoton absorption rate.Comment: 14 pages, 7 figures, submitted, v2: rewritten in response to
referees' comments, v3: rewritten and extended, v4: accepted by Physical
Review
Adaptive phase estimation is more accurate than non-adaptive phase estimation for continuous beams of light
We consider the task of estimating the randomly fluctuating phase of a
continuous-wave beam of light. Using the theory of quantum parameter
estimation, we show that this can be done more accurately when feedback is used
(adaptive phase estimation) than by any scheme not involving feedback
(non-adaptive phase estimation) in which the beam is measured as it arrives at
the detector. Such schemes not involving feedback include all those based on
heterodyne detection or instantaneous canonical phase measurements. We also
demonstrate that the superior accuracy adaptive phase estimation is present in
a regime conducive to observing it experimentally.Comment: 15 pages, 9 figures, submitted to PR
Generation and manipulation of squeezed states of light in optical networks for quantum communication and computation
We analyze a fiber-optic component which could find multiple uses in novel
information-processing systems utilizing squeezed states of light. Our approach
is based on the phenomenon of photon-number squeezing of soliton noise after
the soliton has propagated through a nonlinear optical fiber. Applications of
this component in optical networks for quantum computation and quantum
cryptography are discussed.Comment: 12 pages, 2 figures; submitted to Journal of Optics
Scheme for teleportation of quantum states onto a mechanical resonator
We propose an experimentally feasible scheme to teleport an unkown quantum
state onto the vibrational degree of freedom of a macroscopic mirror. The
quantum channel between the two parties is established by exploiting radiation
pressure effects.Comment: 5 pages, 2 figures, in press on PR
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