6,804 research outputs found
Studies of waveform requirements for intermediate mass-ratio coalescence searches with advanced detectors
The coalescence of a stellar-mass compact object into an intermediate-mass
black hole (intermediate mass-ratio coalescence; IMRAC) is an important
astrophysical source for ground-based gravitational-wave interferometers in the
so-called advanced configuration. However, the ability to carry out effective
matched-filter based searches for these systems is limited by the lack of
reliable waveforms. Here we consider binaries in which the intermediate-mass
black hole has mass in the range 24 - 200 solar masses with a stellar-mass
companion having masses in the range 1.4 - 18.5 solar masses. In addition, we
constrain the mass ratios, q, of the binaries to be in the range 1/140 < q <
1/10 and we restrict our study to the case of circular binaries with
non-spinning components. We investigate the relative contribution to the
signal-to-noise ratio (SNR) of the three different phases of the coalescence:
inspiral, merger and ringdown. We show that merger and ringdown contribute to a
substantial fraction of the total SNR over a large portion of the mass
parameter space, although in a limited portion the SNR is dominated by the
inspiral phase. We further identify three regions in the IMRAC mass-space in
which: (i) inspiral-only searches could be performed with losses in detection
rates L in the range 10% < L < 27%, (ii) searches based on inspiral-only
templates lead to a loss in detection rates in the range 27% < L < 50%$, and
(iii) templates that include merger and ringdown are essential to prevent
losses in detection rates greater than 50%. We investigate the effectiveness
with which the inspiral-only portion of the IMRAC waveform space is covered by
comparing several existing waveform families in this regime. Our results
reinforce the importance of extensive numerical relativity simulations of
IMRACs and the need for further studies of suitable approximation schemes in
this mass range.Comment: 10 pages, 3 figure
Spatial quantum correlations in multiple scattered light
We predict a new spatial quantum correlation in light propagating through a
multiple scattering random medium. The correlation depends on the quantum state
of the light illuminating the medium, is infinite range, and dominates over
classical mesoscopic intensity correlations. The spatial quantum correlation is
revealed in the quantum fluctuations of the total transmission or reflection
through the sample and should be readily observable experimentally.Comment: Reference adde
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
Multispace and Multilevel BDDC
BDDC method is the most advanced method from the Balancing family of
iterative substructuring methods for the solution of large systems of linear
algebraic equations arising from discretization of elliptic boundary value
problems. In the case of many substructures, solving the coarse problem exactly
becomes a bottleneck. Since the coarse problem in BDDC has the same structure
as the original problem, it is straightforward to apply the BDDC method
recursively to solve the coarse problem only approximately. In this paper, we
formulate a new family of abstract Multispace BDDC methods and give condition
number bounds from the abstract additive Schwarz preconditioning theory. The
Multilevel BDDC is then treated as a special case of the Multispace BDDC and
abstract multilevel condition number bounds are given. The abstract bounds
yield polylogarithmic condition number bounds for an arbitrary fixed number of
levels and scalar elliptic problems discretized by finite elements in two and
three spatial dimensions. Numerical experiments confirm the theory.Comment: 26 pages, 3 figures, 2 tables, 20 references. Formal changes onl
Quantum information processing using frequency control of impurity spins in diamond
Spin degrees of freedom of charged nitrogen-vacancy (NV) centers in
diamond have large decoherence times even at room temperature, can be
initialized and read out using optical fields, and are therefore a promising
candidate for solid state qubits. Recently, quantum manipulations of NV-
centers using RF fields were experimentally realized. In this paper we show;
first, that such operations can be controlled by varying the frequency of the
signal, instead of its amplitude, and NV- centers can be selectively
addressed even with spacially uniform RF signals; second, that when several \NV
- centers are placed in an off-resonance optical cavity, a similar application
of classical optical fields provides a controlled coupling and enables a
universal two-qubit gate (CPHASE). RF and optical control together promise a
scalable quantum computing architecture
Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage
Coherent control of collective spontaneous emission in an extended atomic
ensemble resonantly interacting with single-photon wave packets is analyzed. A
scheme for coherent manipulation of collective atomic states is developed such
that superradiant states of the atomic system can be converted into subradiant
ones and vice versa. Possible applications of such a scheme for optical quantum
state storage and single-photon wave packet shaping are discussed. It is shown
that also in the absence of inhomogeneous broadening of the resonant line,
single-photon wave packets with arbitrary pulse shape may be recorded as a
subradiant state and reconstructed even although the duration of the wave
packets is larger than the superradiant life-time. Specifically the
applicability for storing time-bin qubits, which are used in quantum
cryptography is analyzed.Comment: 11 pages, 4 figures, submitted to PR
A versatile source of polarization-entangled photons
We propose a method for the generation of a large variety of entangled
states, encoded in the polarization degrees of freedom of N photons, within the
same experimental setup. Starting with uncorrelated photons, emitted from N
arbitrary single photon sources, and using linear optical tools only, we
demonstrate the creation of all symmetric states, e.g., GHZ- and W-states, as
well as all symmetric and non-symmetric total angular momentum eigenstates of
the N qubit compound.Comment: 4 pages, 3 figure
Spatial wave intensity correlations in quasi-one-dimensional wires
Spatial intensity correlations between waves transmitted through random media
are analyzed within the framework of the random matrix theory of transport.
Assuming that the statistical distribution of transfer matrices is isotropic,
we found that the spatial correlation function can be expressed as the sum of
three terms, with distinctive spatial dependences. This result coincides with
the one obtained in the diffusive regime from perturbative calculations, but
holds all the way from quasi-ballistic transport to localization. While
correlations are positive in the diffusive regime, we predict a transition to
negative correlations as the length of the system decreases.Comment: 10 pages, 3 figures. Submitted to Physical Review Letter
Topological phase for entangled two-qubit states and the representation of the SO(3)group
We discuss the representation of the group by two-qubit maximally
entangled states (MES). We analyze the correspondence between and the
set of two-qubit MES which are experimentally realizable. As a result, we offer
a new interpretation of some recently proposed experiments based on MES.
Employing the tools of quantum optics we treat in terms of two-qubit MES some
classical experiments in neutron interferometry, which showed the -phase
accrued by a spin- particle precessing in a magnetic field. By so doing,
we can analyze the extent to which the recently proposed experiments - and
future ones of the same sort - would involve essentially new physical aspects
as compared with those performed in the past. We argue that the proposed
experiments do extend the possibilities for displaying the double connectedness
of , although for that to be the case it results necessary to map
elements of onto physical operations acting on two-level systems.Comment: 25 pages, 9 figure
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