8,386 research outputs found

### Transform-Limited-Pulse Representation of Excitation with Natural Incoherent Light

We study the natural excitation of molecular systems, applicable to, for
example, photosynthetic light-harvesting complexes, by natural incoherent
light. In contrast with the conventional classical models, we show that the
light need not have random character to properly represent the resultant linear
excitation. Rather, thermal excitation can be interpreted as a collection of
individual events resulting from the system's interaction with individual,
deterministic pulsed realizations that constitute the field. The derived
expressions for the individual field realizations and excitation events allow
for a wave function formalism, and therefore constitute a useful calculational
tool to study dynamics following thermal-light excitation. Further, they
provide a route to the experimental determination of natural incoherent
excitation using pulsed laser techniques.Comment: 5 pages, 3 figures, 1 page supplementary information. Comments
welcom

### Nonclassical and nonlocal effects in the interference of light

Although we tend to think of optical interference as a classical wave phenomenon, recent experiments have revealed a number of effects that are not describable in classical terms. This is particularly true of interference effects involving the detection of a photon pair. We shall refer to them as fourth order interference, on the grounds that the joint probability density for the detection of one photon at r sub 1 at time t and another r sub 2 at time t is proportional to the fourth order correlation function of the field. This probability is readily measured when two photodetectors are positioned at r sub 1 and r sub 2 and the signals from the two detectors are fed to a coincidence counter that registers 'simultaneous' detections by the two detectors in coincidence. The topics covered include: fourth order interference measurements; the Franson experiment; and experimental test of the de Broglie guided wave theory

### Nonclassicality of a photon-subtracted Gaussian field

Published versio

### Interference and the lossless lossy beam splitter

By directing the input light into a particular mode it is possible to obtain
as output all of the input light for a beam splitter that is 50% absorbing.
This effect is also responsible for nonlinear quantum interference when two
photons are incident on the beam splitter.Comment: 10 pages, 2 figures, to appear in J. Mod. Op

### Interference fringes with maximal contrast at finite coherence time

Interference fringes can result from the measurement of four-time fourth-order correlation functions of a wave field. These fringes have a statistical origin and, as a consequence, they show the greatest contrast when the coherence time of the field is finite. A simple acoustic experiment is presented in which these fringes are observed, and it is demonstrated that the contrast is maximal for partial coherence. Random telegraph phase noise is used to vary the field coherence in order to highlight the problem of interpreting this interference; for this noise, the Gaussian moment theorem may not be invoked to reduce the description of the interference to one in terms of first-order interference.M.W. Hamilto

### From Monomials to Words to graphs

Given a finite alphabet X and an ordering on the letters, the map \sigma
sends each monomial on X to the word that is the ordered product of the letter
powers in the monomial. Motivated by a question on Groebner bases, we
characterize ideals I in the free commutative monoid (in terms of a generating
set) such that the ideal generated by \sigma(I) in the free monoid
is finitely generated. Whether there exists an ordering such that
is finitely generated turns out to be NP-complete. The latter problem is
closely related to the recognition problem for comparability graphs.Comment: 27 pages, 2 postscript figures, uses gastex.st

### Hierarchical analysis of gravitational-wave measurements of binary black hole spin-orbit misalignments

Binary black holes may form both through isolated binary evolution and
through dynamical interactions in dense stellar environments. The formation
channel leaves an imprint on the alignment between the black hole spins and the
orbital angular momentum. Gravitational waves from these systems directly
encode information about the spin--orbit misalignment angles, allowing them to
be (weakly) constrained. Identifying sub-populations of spinning binary black
holes will inform us about compact binary formation and evolution. We simulate
a mixed population of binary black holes with spin--orbit misalignments
modelled under a range of assumptions. We then develop a hierarchical analysis
and apply it to mock gravitational-wave observations of these populations.
Assuming a population with dimensionless spin magnitudes of $\chi = 0.7$, we
show that tens of observations will make it possible to distinguish the
presence of subpopulations of coalescing binary black holes based on their spin
orientations. With $100$ observations it will be possible to infer the relative
fraction of coalescing binary black holes with isotropic spin directions
(corresponding to dynamical formation in our models) with a fractional
uncertainty of $\sim 40\%$. Meanwhile, only $\sim 5$ observations are
sufficient to distinguish between extreme models---all binary black holes
either having exactly aligned spins or isotropic spin directions.Comment: 12 pages, 9 figures. Updated to match version published in MNRAS as
10.1093/mnras/stx176

### Quantum Bayesian methods and subsequent measurements

After a derivation of the quantum Bayes theorem, and a discussion of the
reconstruction of the unknown state of identical spin systems by repeated
measurements, the main part of this paper treats the problem of determining the
unknown phase difference of two coherent sources by photon measurements. While
the approach of this paper is based on computing correlations of actual
measurements (photon detections), it is possible to derive indirectly a
probability distribution for the phase difference. In this approach, the
quantum phase is not an observable, but a parameter of an unknown quantum
state. Photon measurements determine a probability distribution for the phase
difference. The approach used in this paper takes into account both photon
statistics and the finite efficiency of the detectors.Comment: Expanded and corrected version. 13 pages, 1 figur

### Verifying the no-hair property of massive compact objects with intermediate-mass-ratio inspirals in advanced gravitational-wave detectors

The detection of gravitational waves from the inspiral of a neutron star or
stellar-mass black hole into an intermediate-mass black hole (IMBH) promises an
entirely new look at strong-field gravitational physics. Gravitational waves
from these intermediate-mass-ratio inspirals (IMRIs), systems with mass ratios
from ~10:1 to ~100:1, may be detectable at rates of up to a few tens per year
by Advanced LIGO/Virgo and will encode a signature of the central body's
spacetime. Direct observation of the spacetime will allow us to use the
"no-hair" theorem of general relativity to determine if the IMBH is a Kerr
black hole (or some more exotic object, e.g. a boson star). Using modified
post-Newtonian (pN) waveforms, we explore the prospects for constraining the
central body's mass-quadrupole moment in the advanced-detector era. We use the
Fisher information matrix to estimate the accuracy with which the parameters of
the central body can be measured. We find that for favorable mass and spin
combinations, the quadrupole moment of a non-Kerr central body can be measured
to within a ~15% fractional error or better using 3.5 pN order waveforms; on
the other hand, we find the accuracy decreases to ~100% fractional error using
2 pN waveforms, except for a narrow band of values of the best-fit non-Kerr
quadrupole moment.Comment: Second version, 12 pages, 5 figures, accepted by PR

### Quantum cryptographic ranging

We present a system to measure the distance between two parties that allows
only trusted people to access the result. The security of the protocol is
guaranteed by the complementarity principle in quantum mechanics. The protocol
can be realized with available technology, at least as a proof of principle
experiment.Comment: 2 pages, 1 figure. Contribution to the proceedings of the IV edition
of the Garda Lake Workshop "Mysteries, Puzzles and Paradoxes in Quantum
Mechanics

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