178 research outputs found
Quantum-limited force measurement with an optomechanical device
We study the detection of weak coherent forces by means of an optomechanical
device formed by a highly reflecting isolated mirror shined by an intense and
highly monochromatic laser field. Radiation pressure excites a vibrational mode
of the mirror, inducing sidebands of the incident field, which are then
measured by heterodyne detection. We determine the sensitivity of such a scheme
and show that the use of an entangled input state of the two sideband modes
improves the detection, even in the presence of damping and noise acting on the
mechanical mode.Comment: 8 pages, 4 figure
Squeezing of a coupled state of two spinors
The notion of spin squeezing involves reduction in the uncertainty of a
component of the spin vector below a certain limit. This aspect has been
studied earlier for pure and mixed states of definite spin. In this paper, this
study has been extended to coupled spin states which do not possess sharp spin
value. A general squeezing criterion has been obtained by requiring that a
direct product state for two spinors is not squeezed. The squeezing aspect of
entangled states is studied in relation to their spin- spin correlations.Comment: Typeset in LaTeX 2e using the style iopart, packages
iopams,times,amssymb,graphicx; 17 pages, 5 eps figure file
Squeezing arbitrary cavity-field states through their interaction with a single driven atom
We propose an implementation of the parametric amplification of an arbitrary
radiation-field state previously prepared in a high-Q cavity. This nonlinear
process is accomplished through the dispersive interactions of a single
three-level atom (fundamental |g>, intermediate |i>, and excited |e> levels)
simultaneously with i) a classical driving field and ii) a previously prepared
cavity mode whose state we wish to squeeze. We show that, in the adiabatic
approximantion, the preparation of the initial atomic state in the intermediate
level |i> becomes crucial for obtaing the degenerated parametric amplification
process.Comment: Final published versio
Squeezed States for General Systems
We propose a ladder-operator method for obtaining the squeezed states of
general symmetry systems. It is a generalization of the annihilation-operator
technique for obtaining the coherent states of symmetry systems. We connect
this method with the minimum-uncertainty method for obtaining the squeezed and
coherent states of general potential systems, and comment on the distinctions
between these two methods and the displacement-operator method.Comment: 8 pages, LAUR-93-1721, LaTe
Retrodictively Optimal Localisations in Phase Space
In a previous paper it was shown that the distribution of measured values for
a retrodictively optimal simultaneous measurement of position and momentum is
always given by the initial state Husimi function. This result is now
generalised to retrodictively optimal simultaneous measurements of an arbitrary
pair of rotated quadratures x_theta1 and x_theta2. It is shown, that given any
such measurement, it is possible to find another such measurement,
informationally equivalent to the first, for which the axes defined by the two
quadratures are perpendicular. It is further shown that the distribution of
measured values for such a meaurement belongs to the class of generalised
Husimi functions most recently discussed by Wuensche and Buzek. The class
consists of the subset of Wodkiewicz's operational probability distributions
for which the filter reference state is a squeezed vaccuum state.Comment: 11 pages, 2 figures. AMS Latex. Replaced with published versio
Generalized Husimi Functions: Analyticity and Information Content
The analytic properties of a class of generalized Husimi functions are
discussed, with particular reference to the problem of state reconstruction.
The class consists of the subset of Wodkiewicz's operational probability
distributions for which the filter reference state is a squeezed vacuum state.
The fact that the function is analytic means that perfectly precise knowledge
of its values over any small region of phase space provides enough information
to reconstruct the density matrix. If, however, one only has imprecise
knowledge of its values, then the amplification of statistical errors which
occurs when one attempts to carry out the continuation seriously limits the
amount of information which can be extracted. To take account of this fact a
distinction is made between explicate, or experimentally accessible
information, and information which is only present in implicate, experimentally
inaccessible form. It is shown that an explicate description of various aspects
of the system can be found localised on various 2 real dimensional surfaces in
complexified phase space. In particular, the continuation of the function to
the purely imaginary part of complexified phase space provides an explicate
description of the Wigner function.Comment: 16 pages, 2 figures, AMS-latex. Replaced with published versio
Development of ecological indicators for the U.S. Great Lakes coastal region – A summary of applications in Lake Huron
Entangling macroscopic oscillators exploiting radiation pressure
It is shown that radiation pressure can be profitably used to entangle {\it
macroscopic} oscillators like movable mirrors, using present technology. We
prove a new sufficient criterion for entanglement and show that the achievable
entanglement is robust against thermal noise. Its signature can be revealed
using common optomechanical readout apparatus.Comment: 4 pages, 2 eps figures, new separability criterion added, new figure
2, authors list change
Geometric phases for generalized squeezed coherent states
A simple technique is used to obtain a general formula for the Berry phase
(and the corresponding Hannay angle) for an arbitrary Hamiltonian with an
equally-spaced spectrum and appropriate ladder operators connecting the
eigenstates. The formalism is first applied to a general deformation of the
oscillator involving both squeezing and displacement. Earlier results are shown
to emerge as special cases. The analysis is then extended to multiphoton
squeezed coherent states and the corresponding anholonomies deduced.Comment: 15 page
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