Multi-mode density matrices of light via amplitude and phase control

A new method is described for determining the quantum state of correlated multimode radiation by interfering the modes and measuring the statistics of the superimposed fields in four-port balanced homodyne detection. The full information on the $N$-mode quantum state is obtained by controlling both the relative amplitudes and the phases of the modes, which simplifies the reconstruction of density matrices to only $N+1$ Fourier transforms. In particular, this method yields time-correlated multimode density matrices of optical pulses by superimposing the signal by a sequence of short local-oscillator pulses.Comment: 6 pages, late

True photo-counting statistics of multiple on-off detectors

We derive a closed photo-counting formula, including noise counts and a finite quantum efficiency, for photon number resolving detectors based on on-off detectors. It applies to detection schemes such as array detectors and multiplexing setups. The result renders it possible to compare the corresponding measured counting statistics with the true photon number statistics of arbitrary quantum states. The photo-counting formula is applied to the discrimination of photon numbers of Fock states, squeezed states, and odd coherent states. It is illustrated for coherent states that our formula is indispensable for the correct interpretation of quantum effects observed with such devices.Comment: 7 pages, 4 figure

Probing r-Process Production of Nuclei Beyond Bi209 with Gamma Rays

We estimate gamma-ray fluxes due to the decay of nuclei beyond Bi209 from a supernova or a supernova remnant assuming that the r-process occurs in supernovae. We find that a detector with a sensitivity of about 10**(-7) photons/cm**2/s at energies of 40 keV to 3 MeV may detect fluxes due to the decay of Ra226, Th229, Am241, Am243, Cf249, and Cf251 in the newly discovered supernova remnant near Vela. In addition, such a detector may detect fluxes due to the decay of Ac227 and Ra228 produced in a future supernova at a distance of about 1 kpc. As nuclei with mass numbers A > 209 are produced solely by the r-process, such detections are the best proof for a supernova r-process site. Further, they provide the most direct information on yields of progenitor nuclei with A > 209 at r-process freeze-out. Finally, detection of fluxes due to the decay of r-process nuclei over a range of masses from a supernova or a supernova remnant provides the opportunity to compare yields in a single supernova event with the solar r-process abundance pattern.Comment: 24 pages, 3 figures, to appear in the October 10, 1999 issue of Ap