2,669 research outputs found
Signatures of Hong-Ou-Mandel Interference at Microwave Frequencies
Two-photon quantum interference at a beam splitter, commonly known as
Hong-Ou-Mandel interference, was recently demonstrated with
\emph{microwave-frequency} photons by Lang \emph{et
al.}\,\cite{lang:microwaveHOM}. This experiment employed circuit QED systems as
sources of microwave photons, and was based on the measurement of second-order
cross-correlation and auto-correlation functions of the microwave fields at the
outputs of the beam splitter. Here we present the calculation of these
correlation functions for the cases of inputs corresponding to: (i) trains of
\emph{pulsed} Gaussian or Lorentzian single microwave photons, and (ii)
resonant fluorescent microwave fields from \emph{continuously-driven} circuit
QED systems. The calculations include the effects of the finite bandwidth of
the detection scheme. In both cases, the signature of two-photon quantum
interference is a suppression of the second-order cross-correlation function
for small delays. The experiment described in Ref.
\onlinecite{lang:microwaveHOM} was performed with trains of \emph{Lorentzian}
single photons, and very good agreement between the calculations and the
experimental data was obtained.Comment: 11 pages, 3 figure
Propagation of sound through a sheared flow
Sound generated in a moving fluid must propagate through a shear layer in order to be measured by a fixed instrument. These propagation effects were evaluated for noise sources typically associated with single and co-flowing subsonic jets and for subcritical flow over airfoils in such jets. The techniques for describing acoustic propagation fall into two categories: geometric acoustics and wave acoustics. Geometric acoustics is most convenient and accurate for high frequency sound. In the frequency range of interest to the present study (greater than 150 Hz), the geometric acoustics approach was determined to be most useful and practical
Evaluation of the 50km/h default urban speed limit in South Australia
On the 1st March 2003 the Default Urban Speed Limit (DUSL) in South Australia was lowered from 60 km/h to 50 km/h. Since this date, all urban roads have a speed limit of 50 km/h unless otherwise signed. This paper reports the results of an evaluation of the effectiveness of the reduced DUSL and is based on speed surveys and crash data analysis. Vehicles speeds were measured at 52 randomly chosen sites across the State. Crash data was analysed by examining the crash history of all roads with a 50 km/h or 60 km/h speed limit, a year before and after the new DUSL was introduced. The study found that, on average, mean speeds have fallen by approximately 2.2 km/h on streets where the speed limit was reduced and by 0.7 km/h on arterial roads where 60 km/h speed limit signs were erected. There was a 19.8% reduction in casualty crashes on 50 km/h roads and a corresponding 4.6% reduction on 60 km/h arterial roads when compared with the previous year.C. Kloeden, J. Woolley and J. McLea
Continuous quantum non-demolition measurement of Fock states of a nanoresonator using feedback-controlled circuit QED
We propose a scheme for the quantum non-demolition (QND) measurement of Fock
states of a nanomechanical resonator via feedback control of a coupled circuit
QED system. A Cooper pair box (CPB) is coupled to both the nanoresonator and
microwave cavity. The CPB is read-out via homodyne detection on the cavity and
feedback control is used to effect a non-dissipative measurement of the CPB.
This realizes an indirect QND measurement of the nanoresonator via a
second-order coupling of the CPB to the nanoresonator number operator. The
phonon number of the Fock state may be determined by integrating the stochastic
master equation derived, or by processing of the measurement signal.Comment: 5 pages, 3 figure
Count three for wear able computers
This paper is a postprint of a paper submitted to and accepted for publication in the Proceedings of the IEE Eurowearable 2003 Conference, and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.
A revised version of this paper was also published in Electronics Systems and Software, also subject to Institution of Engineering and Technology Copyright. The copy of record is also available at the IET Digital Library.A description of 'ubiquitous computer' is presented. Ubiquitous computers imply portable computers embedded into everyday objects, which would replace personal computers. Ubiquitous computers can be mapped into a three-tier scheme, differentiated by processor performance and flexibility of function. The power consumption of mobile devices is one of the most important design considerations. The size of a wearable system is often a design limitation
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