228 research outputs found
Bethe Ansatz solution of a decagonal rectangle triangle random tiling
A random tiling of rectangles and triangles displaying a decagonal phase is
solved by Bethe Ansatz. Analogously to the solutions of the dodecagonal square
triangle and the octagonal rectangle triangle tiling an exact expression for
the maximum of the entropy is found.Comment: 17 pages, 4 figures, some remarks added and typos correcte
Exact Solution of an Octagonal Random Tiling Model
We consider the two-dimensional random tiling model introduced by Cockayne,
i.e. the ensemble of all possible coverings of the plane without gaps or
overlaps with squares and various hexagons. At the appropriate relative
densities the correlations have eight-fold rotational symmetry. We reformulate
the model in terms of a random tiling ensemble with identical rectangles and
isosceles triangles. The partition function of this model can be calculated by
diagonalizing a transfer matrix using the Bethe Ansatz (BA). The BA equations
can be solved providing {\em exact} values of the entropy and elastic
constants.Comment: 4 pages,3 Postscript figures, uses revte
Pound-locking for characterization of superconducting microresonators
We present a new application and implementation of the so-called Pound
locking technique for the interrogation of superconducting microresonators. We
discuss how by comparing against stable frequency sources this technique can be
used to characterize properties of resonators that can not be accessed using
traditional methods. Specifically, by analyzing the noise spectra and the Allan
deviation we obtain valuable information about the nature of the noise in
superconducting planar resonators. This technique also greatly improves the
read-out accuracy and measurement throughput compared to conventional methods.Comment: 5 page
Observation of Periodic Orbits on Curved Two - dimensional Geometries
We measure elastomechanical spectra for a family of thin shells. We show that
these spectra can be described by a "semiclassical" trace formula comprising
periodic orbits on geodesics, with the periods of these orbits consistent with
those extracted from experiment. The influence of periodic orbits on spectra in
the case of two-dimensional curved geometries is thereby demonstrated, where
the parameter corresponding to Planck's constant in quantum systems involves
the wave number and the curvature radius. We use these findings to explain the
marked clustering of levels when the shell is hemispherical
JEM-X background models
Background and determination of its components for the JEM-X X-ray telescope
on INTEGRAL are discussed. A part of the first background observations by JEM-X
are analysed and results are compared to predictions. The observations are
based on extensive imaging of background near the Crab Nebula on revolution 41
of INTEGRAL. Total observing time used for the analysis was 216502 s, with the
average of 25 cps of background for each of the two JEM-X telescopes. JEM-X1
showed slightly higher average background intensity than JEM-X2. The detectors
were stable during the long exposures, and weak orbital phase dependence in the
background outside radiation belts was observed. The analysis yielded an
average of 5 cps for the diffuse background, and 20 cps for the instrument
background. The instrument background was found highly dependent on position,
both for spectral shape and intensity. Diffuse background was enhanced in the
central area of a detector, and it decreased radially towards the edge, with a
clear vignetting effect for both JEM-X units. The instrument background was
weakest in the central area of a detector and showed a steep increase at the
very edges of both JEM-X detectors, with significant difference in spatial
signatures between JEM-X units. According to our modelling, instrument
background dominates over diffuse background in all positions and for all
energies of JEM-X.Comment: 4 pages, 3 figures, A&A accepted (INTEGRAL special issue
Generating Single Microwave Photons in a Circuit
Electromagnetic signals in circuits consist of discrete photons, though
conventional voltage sources can only generate classical fields with a coherent
superposition of many different photon numbers. While these classical signals
can control and measure bits in a quantum computer (qubits), single photons can
carry quantum information, enabling non-local quantum interactions, an
important resource for scalable quantum computing. Here, we demonstrate an
on-chip single photon source in a circuit quantum electrodynamics (QED)
architecture, with a microwave transmission line cavity that collects the
spontaneous emission of a single superconducting qubit with high efficiency.
The photon source is triggered by a qubit rotation, as a photon is generated
only when the qubit is excited. Tomography of both qubit and fluorescence
photon shows that arbitrary qubit states can be mapped onto the photon state,
demonstrating an ability to convert a stationary qubit into a flying qubit.
Both the average power and voltage of the photon source are characterized to
verify performance of the system. This single photon source is an important
addition to a rapidly growing toolbox for quantum optics on a chip.Comment: 6 pages, 5 figures, hires version at
http://www.eng.yale.edu/rslab/papers/single_photon_hires.pd
Spectral structure and decompositions of optical states, and their applications
We discuss the spectral structure and decomposition of multi-photon states.
Ordinarily `multi-photon states' and `Fock states' are regarded as synonymous.
However, when the spectral degrees of freedom are included this is not the
case, and the class of `multi-photon' states is much broader than the class of
`Fock' states. We discuss the criteria for a state to be considered a Fock
state. We then address the decomposition of general multi-photon states into
bases of orthogonal eigenmodes, building on existing multi-mode theory, and
introduce an occupation number representation that provides an elegant
description of such states that in many situations simplifies calculations.
Finally we apply this technique to several example situations, which are highly
relevant for state of the art experiments. These include Hong-Ou-Mandel
interference, spectral filtering, finite bandwidth photo-detection, homodyne
detection and the conditional preparation of Schr\"odinger Kitten and Fock
states. Our techniques allow for very simple descriptions of each of these
examples.Comment: 12 page
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