111 research outputs found
Experiment on Interaction-Free Measurement in Neutron Interferometry
A neutron interferometric test of interaction-free detection of the presence
of an absorbing object in one arm of a neutron interferometer has been
performed. Despite deviations from the ideal performance characteristics of a
Mach-Zehnder interferometer it could be shown that information is obtained
without interaction.Comment: 8 pages, 4 postscript figures; submitted to Phys.Lett.A; Figures
contained only in replaced versio
Nonclassical interaction-free detection of objects in a monolithic total-internal-reflection resonator
We show that with an efficiency exceeding 99% one can use a monolithic
total-internal-reflection resonator in order to ascertain the presence of an
object without transferring a quantum of energy to it. We also propose an
experiment on the probabilistic meaning of the electric field that contains
only a very few photons.Comment: RevTeX, 13 pages, 4 ps figures, author's www:
http://m3k.grad.hr/pavici
Hyperentangled Bell-state analysis
It is known that it is impossible to unambiguously distinguish the four Bell
states encoded in pairs of photon polarizations using only linear optics.
However, hyperentanglement, the simultaneous entanglement in more than one
degree of freedom, has been shown to assist the complete Bell analysis of the
four Bell states (given a fixed state of the other degrees of freedom). Yet
introducing other degrees of freedom also enlarges the total number of
Bell-like states. We investigate the limits for unambiguously distinguishing
these Bell-like states. In particular, when the additional degree of freedom is
qubit-like, we find that the optimal one-shot discrimination schemes are to
group the 16 states into 7 distinguishable classes, and that an unambiguous
discrimination is possible with two identical copies.Comment: typos corrected, to appear in PRA, 5 pages, 2 figures, 2 table
Atomic vapor-based high efficiency optical detectors with photon number resolution
We propose a novel approach to the important fundamental problem of detecting
weak optical fields at the few photon level. The ability to detect with high
efficiency (>99%), and to distinguish the number of photons in a given time
interval is a very challenging technical problem with enormous potential
pay-offs in quantum communications and information processing. Our proposal
diverges from standard solid-state photo-detector technology by employing an
atomic vapor as the active medium, prepared in a specific quantum state using
laser radiation. The absorption of a photon will be aided by a dressing laser,
and the presence or absence of an excited atom will be detected using the
``cycling transition'' approach perfected for ion traps. By first incorporating
an appropriate upconversion scheme, our method can be applied to a wide variety
of optical wavelengths.Comment: 4 pages, 2 figure
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