291 research outputs found
A new type of quantum speed meter interferometer: measuring speed to search for intermediate mass black holes
The recent discovery of gravitational waves (GW) by LIGO has impressively
launched the novel field of gravitational astronomy and it allowed us to
glimpse at exciting objects we could so far only speculate about. Further
sensitivity improvements at the low frequency end of the detection band of
future GW observatories rely on quantum non-demolition (QND) methods to
suppress fundamental quantum fluctuations of the light fields used to readout
the GW signal. Here we invent a novel concept of how to turn a conventional
Michelson interferometer into a QND speed meter interferometer with coherently
suppressed quantum back-action noise by using two orthogonal polarisations of
light and an optical circulator to couple them. We carry out a detailed
analysis of how imperfections and optical loss influence the achievable
sensitivity and find that the configuration proposed here would significantly
enhance the low frequency sensitivity and increase the observable event rate of
binary black hole coalescences in the range of by a factor
of up to .Comment: 8 pages, 5 figures. Modified figures and text in v
Charged particle (pseudo-)rapidity distributions in proton+anti-proton/proton+proton and Pb+Pb/Au+Au collisions from SPS to LHC energies from UrQMD
We present results for final state charged particle (pseudo-)rapidity
distributions in + / + and
Pb+Pb/Au+Au at ultra high energies (17.3 GeV
14 TeV) from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD-v2.3)
model. In addition, excitation functions of produced charged particle
multiplicities () and pseudorapidity spectra are investigated up
to LHC energies. Good agreement is observed between UrQMD and measured
pseudorapidity distributions of charged particles up to the highest Tevatron
and SpS energies.Comment: 6 pages, 7 figure
Observation of a Chiral State in a Microwave Cavity
A microwave experiment has been realized to measure the phase difference of
the oscillating electric field at two points inside the cavity. The technique
has been applied to a dissipative resonator which exhibits a singularity --
called exceptional point -- in its eigenvalue and eigenvector spectrum. At the
singularity, two modes coalesce with a phase difference of We
conclude that the state excited at the singularity has a definitiv chirality.Comment: RevTex 4, 5 figure
Encircling an Exceptional Point
We calculate analytically the geometric phases that the eigenvectors of a
parametric dissipative two-state system described by a complex symmetric
Hamiltonian pick up when an exceptional point (EP) is encircled. An EP is a
parameter setting where the two eigenvalues and the corresponding eigenvectors
of the Hamiltonian coalesce. We show that it can be encircled on a path along
which the eigenvectors remain approximately real and discuss a microwave cavity
experiment, where such an encircling of an EP was realized. Since the
wavefunctions remain approximately real, they could be reconstructed from the
nodal lines of the recorded spatial intensity distributions of the electric
fields inside the resonator. We measured the geometric phases that occur when
an EP is encircled four times and thus confirmed that for our system an EP is a
branch point of fourth order.Comment: RevTex 4.0, four eps-figures (low resolution
Local-Oscillator Noise Coupling in Balanced Homodyne Readout for Advanced Gravitational Wave Detectors
The second generation of interferometric gravitational wave detectors are
quickly approaching their design sensitivity. For the first time these
detectors will become limited by quantum back-action noise. Several back-action
evasion techniques have been proposed to further increase the detector
sensitivity. Since most proposals rely on a flexible readout of the full
amplitude- and phase-quadrature space of the output light field, balanced
homodyne detection is generally expected to replace the currently used DC
readout. Up to now, little investigation has been undertaken into how balanced
homodyne detection can be successfully transferred from its ubiquitous
application in table-top quantum optics experiments to large-scale
interferometers with suspended optics. Here we derive implementation
requirements with respect to local oscillator noise couplings and highlight
potential issues with the example of the Glasgow Sagnac Speed Meter experiment,
as well as for a future upgrade to the Advanced LIGO detectors.Comment: 7 pages, 5 figure
Experimental Test of a Trace Formula for a Chaotic Three Dimensional Microwave Cavity
We have measured resonance spectra in a superconducting microwave cavity with
the shape of a three-dimensional generalized Bunimovich stadium billiard and
analyzed their spectral fluctuation properties. The experimental length
spectrum exhibits contributions from periodic orbits of non-generic modes and
from unstable periodic orbit of the underlying classical system. It is well
reproduced by our theoretical calculations based on the trace formula derived
by Balian and Duplantier for chaotic electromagnetic cavities.Comment: 4 pages, 5 figures (reduced quality
Effects of static and dynamic higher-order optical modes in balanced homodyne readout for future gravitational waves detectors
With the recent detection of Gravitational waves (GW), marking the start of the new field of GW astronomy, the push for building more sensitive laser-interferometric gravitational wave detectors (GWD) has never been stronger. Balanced homodyne detection (BHD) allows for a quantum noise (QN) limited readout of arbitrary light field quadratures, and has therefore been suggested as a vital building block for upgrades to Advanced LIGO and third generation observatories. In terms of the practical implementation of BHD, we develop a full framework for analyzing the static optical high order modes (HOMs) occurring in the BHD paths related to the misalignment or mode matching at the input and output ports of the laser interferometer. We find the effects of HOMs on the quantum noise limited sensitivity is independent of the actual interferometer configuration, e.g. Michelson and Sagnac interferometers are effected in the same way. We show that misalignment of the output ports of the interferometer (output misalignment) only effects the high frequency part of the quantum noise limited sensitivity (detection noise). However, at low frequencies, HOMs reduce the interferometer response and the radiation pressure noise (back action noise) by the same amount and hence the quantum noise limited sensitivity is not negatively effected in that frequency range. We show that the misalignment of laser into the interferometer (input misalignment) produces the same effect as output misalignment and additionally decreases the power inside the interferometer. We also analyze dynamic HOM effects, such as beam jitter created by the suspended mirrors of the BHD. Our analyses can be directly applied to any BHD implementation in a future GWD. Moreover, we apply our analytical techniques to the example of the speed meter proof of concept experiment under construction in Glasgow. We find that for our experimental parameters, the performance of our seismic isolation system in the BHD paths is compatible with the design sensitivity of the experiment
First Experimental Evidence for Chaos-Assisted Tunneling in a Microwave Annular Billiard
We report on first experimental signatures for chaos-assisted tunneling in a
two-dimensional annular billiard. Measurements of microwave spectra from a
superconducting cavity with high frequency resolution are combined with
electromagnetic field distributions experimentally determined from a normal
conducting twin cavity with high spatial resolution to resolve eigenmodes with
properly identified quantum numbers. Distributions of so-called quasi-doublet
splittings serve as basic observables for the tunneling between whispering
gallery type modes localized to congruent, but distinct tori which are coupled
weakly to irregular eigenstates associated with the chaotic region in phase
space.Comment: 5 pages RevTex, 5 low-resolution figures (high-resolution figures:
http://linac.ikp.physik.tu-darmstadt.de/heiko/chaospub.html, to be published
in Phys. Rev. Let
Demonstration of a switchable damping system to allow low-noise operation of high-Q low-mass suspension systems
Low mass suspension systems with high-Q pendulum stages are used to enable
quantum radiation pressure noise limited experiments. Utilising multiple
pendulum stages with vertical blade springs and materials with high quality
factors provides attenuation of seismic and thermal noise, however damping of
these high-Q pendulum systems in multiple degrees of freedom is essential for
practical implementation. Viscous damping such as eddy-current damping can be
employed but introduces displacement noise from force noise due to thermal
fluctuations in the damping system. In this paper we demonstrate a passive
damping system with adjustable damping strength as a solution for this problem
that can be used for low mass suspension systems without adding additional
displacement noise in science mode. We show a reduction of the damping factor
by a factor of 8 on a test suspension and provide a general optimisation for
this system.Comment: 5 pages, 5 figure
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