789 research outputs found
Statistical uncertainty in quantum optical photodetection measurements
We present a complete statistical analysis of quantum optical measurement
schemes based on photodetection. Statistical distributions of quantum
observables determined from a finite number of experimental runs are
characterized with the help of the generating function, which we derive using
the exact statistical description of raw experimental outcomes. We use the
developed formalism to point out that the statistical uncertainty results in
substantial limitations of the determined information on the quantum state:
though a family of observables characterizing the quantum state can be safely
evaluated from experimental data, its further use to obtain the expectation
value of some operators generates exploding statistical errors. These issues
are discussed using the example of phase-insensitive measurements of a single
light mode. We study reconstruction of the photon number distribution from
photon counting and random phase homodyne detection. We show that utilization
of the reconstructed distribution to evaluate a simple well-behaved observable,
namely the parity operator, encounters difficulties due to accumulation of
statistical errors. As the parity operator yields the Wigner function at the
phase space origin, this example also demonstrates that transformation between
various experimentally determined representations of the quantum state is a
quite delicate matter.Comment: 18 pages REVTeX, 7 figures included using epsf. Few minor corrections
made, clarified conclusion
axial form factor from bubble chamber experiments
A careful reanalysis of both Argonne National Laboratory and Brookhaven
National Laboratory data for weak single pion production is done. We consider
deuteron nuclear effects and normalization (flux) uncertainties in both
experiments. We demonstrate that these two sets of data are in good agreement.
For the dipole parametrization of , we obtain , GeV. As an application we present the discussion of
the uncertainty of the neutral current 1 production cross section,
important for the T2K neutrino oscillation experiment.Comment: 16 pages, 8 figures, 2 table
The light curve of a transient X-ray source
The Ariel-V satellite monitored the X-ray light curve of A1524-62 almost continuously from 40 days prior to maximum light until its disappearance below the effective experimental sensitivity. The source exhibited maximum light on approximately 4 December 1974, at a level of 0.9 the apparent magnitude of the Crab Nebula in the energy band 3-6 keV. Although similar to previously reported transient sources with a decay time constant of approximately 2 months, the source exhibited an extended, variable pre-flare on-state of about 1 month at a level of greater than approximately 0.1 maximum light. The four bright (greater than 0.2 of the Crab Nebula) transient sources observed during the first half-year of Ariel-V operation are indicative of a galactic disk distribution, and a luminosity at maximum in excess of 10 to the 37th power ergs/sec
Maximum likelihood estimation of photon number distribution from homodyne statistics
We present a method for reconstructing the photon number distribution from
the homodyne statistics based on maximization of the likelihood function
derived from the exact statistical description of a homodyne experiment. This
method incorporates in a natural way the physical constraints on the
reconstructed quantities, and the compensation for the nonunit detection
efficiency.Comment: 3 pages REVTeX. Final version, to appear in Phys. Rev. A as a Brief
Repor
A New Technique for Finding Needles in Haystacks: A Geometric Approach to Distinguishing Between a New Source and Random Fluctuations
We propose a new test statistic based on a score process for determining the
statistical significance of a putative signal that may be a small perturbation
to a noisy experimental background. We derive the reference distribution for
this score test statistic; it has an elegant geometrical interpretation as well
as broad applicability. We illustrate the technique in the context of a model
problem from high-energy particle physics. Monte Carlo experimental results
confirm that the score test results in a significantly improved rate of signal
detection.Comment: 5 pages, 4 figure
Could psoralen plus ultraviolet A1 (“PUVA1”) work? Depth penetration achieved by phototherapy lamps
Funding: PhD Studentship UK EPRSC EP/N509759/1.Psoralen and ultraviolet A (PUVA) is useful in treating various hand and foot skin diseases.1 Most cases of psoriasis respond well to phototherapy or PUVA. However, for some diseases, such as palmoplantar pustular psoriasis, PUVA is not always sufficient to produce therapeutic effect. If PUVA fails, it is sometimes necessary to progress to other treatments such as Grenz ray therapy (where available),2 systemic retinoid or systemic immunosuppression. Could “PUVA1” (psoralen combined with ultraviolet A1 long wavelength ultraviolet A [UVA]) work in cases where conventional PUVA (psoralen plus broadband UVA) has been inadequate?PostprintPeer reviewe
Quantum homodyne tomography with a priori constraints
I present a novel algorithm for reconstructing the Wigner function from
homodyne statistics. The proposed method, based on maximum-likelihood
estimation, is capable of compensating for detection losses in a numerically
stable way.Comment: 4 pages, REVTeX, 2 figure
Minimal, superficial DNA damage in human skin from filtered far-ultraviolet C
Funding: This study was funded in part by MR/P012248/1 to R.P.H. from the Medical Research Council.Publisher PDFPeer reviewe
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