23,475 research outputs found
Photon-number correlations by photon-number resolving detectors
We demonstrate that by using a pair of photodetectors endowed with internal
gain we are able to quantify the correlation coefficient between the two
components of a pulsed bipartite state in the mesoscopic intensity regime (less
than 100 mean photons)
Photon-number tomography and fidelity
The scheme of photon-number tomography is discussed in the framework of
star-product quantization. The connection of dual quantization scheme and
observables is reviewed. The quantizer and dequantizer operators and kernels of
star product of tomograms in photon-number tomography scheme and its dual one
are presented in explicit form. The fidelity and state purity are discussed in
photon{number tomographic scheme, and the expressions for fidelity and purity
are obtained in the form of integral of the product of two photon-number
tomograms with integral kernel which is presented in explicit form. The
properties of quantumness are discussed in terms of inequalities on state
photon{number tomograms.Comment: the paper is submitted for publication in AIP Conference Serie
Quantum key distribution with realistic states: photon-number statistics in the photon-number splitting attack
Quantum key distribution can be performed with practical signal sources such
as weak coherent pulses. One example of such a scheme is the Bennett-Brassard
protocol that can be implemented via polarization of the signals, or equivalent
signals. It turns out that the most powerful tool at the disposition of an
eavesdropper is the photon-number splitting attack. We show that this attack
can be extended in the relevant parameter regime such as to preserve the
Poissonian photon number distribution of the combination of the signal source
and the lossy channel.Comment: 4 page
Density Matrix From Photon Number Tomography
We provide a simple analytic relation which connects the density operator of
the radiation field with the number probabilities. The problem of
experimentally "sampling" a general matrix elements is studied, and the
deleterious effects of nonunit quantum efficiency in the detection process are
analyzed showing how they can be reduced by using the squeezing technique. The
obtained result is particulary useful for intracavity field reconstruction
states.Comment: LATEX,6 pages,accepted by Europhysics Letter
Phase estimation with photon number constraint
Many researches proposed the use of the noon state as the input state for
phase estimation, which is one topic of quantum metrology. This is because the
input noon state provides the maximum Fisher information at the specific point.
However, the Fisher information does not necessarily give the attainable bound
for estimation error. In this paper, we adopt the local asymptotic mini-max
criterion as well as the mini-max criterion, and show that the maximum Fisher
information does not give the attainable bound for estimation error under these
criteria in the phase estimation. We also propose the optimal input state under
the constraints for photon number of the input state instead of the noon state.Comment: Several typos are fixed. New section "ANALYSIS ON NOON STATE" is
adde
Photon number variance in isolated cavities
We consider a strictly isolated single-mode optical cavity resonating at
angular frequency omega containing atoms whose one-electron level energies are
supposed to be: hbar*omega, 2*hbar*omega,...B*hbar\omega, and m photons. If
initially the atoms are in their highest energy state and m=0, we find that at
equilibrium: variance(m)/mean(m)=(B+1)/6, indicating that the internal field
statistics is sub-Poissonian if the number of atomic levels B does not exceed
4. Remarkably, this result does not depend on the number of atoms, nor on the
number of electrons that each atom incorporates. Our result has application to
the statistics of the light emitted by pulsed lasers and nuclear magnetic
resonance. On the mathematical side, the result is based on the restricted
partitions of integers.Comment: 4 pages, to be submitted to Journal of Physics
Photon-number statistics with Silicon photomultipliers
We present a description of the operation of a multi-pixel detector in the
presence of non-negligible dark-count and cross-talk effects. We apply the
model to devise self-consistent calibration strategies to be performed on the
very light under investigation
Photon number conservation and photon interference
The group theoretical aspect of the description of passive lossless optical
four-ports (beam splitters) is revisited. It is shown through an example, that
this approach can be useful in understanding interferometric schemes where a
low number of photons interfere. The formalism is extended to passive lossless
optical six-ports, their SU(3)-theory is outlined.Comment: Contribution at "Classical and Quantum Interference" workshop in RCO,
Olomouc, Oct. 25-26 2001. A corrected versio
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