8,493 research outputs found
Time-bin entangled photon holes
The general concept of entangled photon holes is based on a correlated
absence of photon pairs in an otherwise constant optical background. Here we
consider the specialized case when this background is confined to two
well-defined time bins, which allows the formation of time-bin entangled photon
holes. We show that when the typical coherent state background is replaced by a
true single-photon (Fock state) background, the basic time-bin entangled
photon-hole state becomes equivalent to one of the time-bin entangled
photon-pair states. We experimentally demonstrate these ideas using a
parametric down-conversion photon-pair source, linear optics, and
post-selection to violate a Bell inequality with time-bin entangled photon
holes.Comment: 6 pages, 5 figure
Quantum interference by two temporally distinguishable pulses
We report a two-photon interference effect, in which the entangled photon
pairs are generated from two laser pulses well-separated in time. In a single
pump pulse case, interference effects did not occur in our experimental scheme.
However, by introducing a second pump pulse delayed in time, quantum
interference was then observed. The visibility of the interference fringes
shows dependence on the delay time between two laser pulses. The results are
explained in terms of indistinguishability of biphoton amplitudes which
originated from two temporally separated laser pulses.Comment: two-column, 4pages, submitted to PRA, minor change
New high-efficiency source of photon pairs for engineering quantum entanglement
We have constructed an efficient source of photon pairs using a
waveguide-type nonlinear device and performed a two-photon interference
experiment with an unbalanced Michelson interferometer. Parametric
down-converted photons from the nonlinear device are detected by two detectors
located at the output ports of the interferometer. Because the interferometer
is constructed with two optical paths of different length, photons from the
shorter path arrive at the detector earlier than those from the longer path. We
find that the difference of arrival time and the time window of the coincidence
counter are important parameters which determine the boundary between the
classical and quantum regime. When the time window of the coincidence counter
is smaller than the arrival time difference, fringes of high visibility
(80 10%) were observed. This result is only explained by quantum theory
and is clear evidence for quantum entanglement of the interferometer's optical
paths.Comment: 4 pages, 4 figures, IQEC200
Induced Coherence and Stable Soliton Spiraling
We develop a theory of soliton spiraling in a bulk nonlinear medium and
reveal a new physical mechanism: periodic power exchange via induced coherence,
which can lead to stable spiraling and the formation of dynamical two-soliton
states. Our theory not only explains earlier observations, but provides a
number of predictions which are also verified experimentally. Finally, we show
theoretically and experimentally that soliton spiraling can be controled by the
degree of mutual initial coherence.Comment: 4 pages, 5 figure
Re-Evaluation of Ar-39 - Ar-40 Ages for Apollo Lunar Rocks 15415 and 60015
We re-analyzed 39Ar-40Ar ages of Apollo lunar highland samples 15415 and 60015, two ferroan anorthosites analyzed previously in the 1970 s, with a more detailed approach and with revised decay constants. From these samples we carefully prepared 100-200 mesh mineral separates for analysis at the Noble Gas Laboratory at NASA-Johnson Space Center. The Ar-39-Ar-40 age spectra for 15415 yielded an age of 3851 +/- 38 Ma with 33-99% of Ar39 release, roughly in agreement with previously reported Ar-Ar ages. For 60015, we obtained an age of 3584 +/- 152 Ma in 23-98% of Ar39 release, also in agreement with previously reported Ar-Ar ages of approximately 3.5 Ga. Highland anorthosites like these are believed by many to be the original crust of the moon, formed by plagioclase floatation atop a magma ocean, however the Ar-Ar ages of 15415 and 60015 are considerably younger than lunar crust formation. By contrast, recently recovered lunar anorthosites such as Dhofar 489, Dhofar 908, and Yamato 86032 yield older Ar-Ar ages, up to 4.35 Ga, much closer to time of formation of the lunar crust. It follows that the Ar-Ar ages of the Apollo samples must have been reset by secondary heating, and that this heating affected highland anorthosites at both the Apollo 15 and Apollo 16 landing sites but did not affect lunar highland meteorites. One obvious consideration is that while the Apollo samples were collected from the near side of the moon, these lunar meteorites are thought to have originated from the lunar far sid
Full Quantum Analysis of Two-Photon Absorption Using Two-Photon Wavefunction: Comparison with One-Photon Absorption
For dissipation-free photon-photon interaction at the single photon level, we
analyze one-photon transition and two-photon transition induced by photon pairs
in three-level atoms using two-photon wavefunctions. We show that the
two-photon absorption can be substantially enhanced by adjusting the time
correlation of photon pairs. We study two typical cases: Gaussian wavefunction
and rectangular wavefunction. In the latter, we find that under special
conditions one-photon transition is completely suppressed while the high
probability of two-photon transition is maintained.Comment: 6 pages, 4 figure
Finite resolution measurement of the non-classical polarization statistics of entangled photon pairs
By limiting the resolution of quantum measurements, the measurement induced
changes of the quantum state can be reduced, permitting subsequent measurements
of variables that do not commute with the initially measured property. It is
then possible to experimentally determine correlations between non-commuting
variables. The application of this method to the polarization statistics of
entangled photon pairs reveals that negative conditional probabilities between
non-orthogonal polarization components are responsible for the violation of
Bell's inequalities. Such negative probabilities can also be observed in finite
resolution measurements of the polarization of a single photon. The violation
of Bell's inequalities therefore originates from local properties of the
quantum statistics of single photon polarization.Comment: 15 pages, 5 figures and 1 table, new figure to illustrate results,
improved explanation of statistical analysi
Critical Currents of Josephson-Coupled Wire Arrays
We calculate the current-voltage characteristics and critical current
I_c^{array} of an array of Josephson-coupled superconducting wires. The array
has two layers, each consisting of a set of parallel wires, arranged at right
angles, such that an overdamped resistively-shunted junction forms wherever two
wires cross. A uniform magnetic field equal to f flux quanta per plaquette is
applied perpendicular to the layers. If f = p/q, where p and q are mutually
prime integers, I_c^{array}(f) is found to have sharp peaks when q is a small
integer. To an excellent approximation, it is found in a square array of n^2
plaquettes, that I_c^{array}(f) \propto (n/q)^{1/2} for sufficiently large n.
This result is interpreted in terms of the commensurability between the array
and the assumed q \times q unit cell of the ground state vortex lattice.Comment: 4 pages, 4 figure
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