88 research outputs found
All-optical production of 7Li Bose-Einstein condensation using Feshbach resonances
We show an all-optical method of making 7Li condensate using tunability of
the scattering length in the proximity of a Feshbach resonance. We report the
observation of two new Feshbach resonances on |F = 1;mF = 0> state. The narrow
(broad) resonance of 7 G (34 G) width is detected at 831 +- 4 G (884 +4 -13 G).
Position of the scattering length zero crossing between the resonances is found
at 836 +- 4 G. The broad resonance is shown to be favorable for run away
evaporation which we perform in a crossed-beam optical dipole trap. Starting
directly form the phase space density of a magneto-optical trap we observe a
Bose-Einstein condensation threshold in less than 3 s of forced evaporation.Comment: 5 pages, 5 figure
Nuclear-spin-independent short-range three-body physics in ultracold atoms
We investigate three-body recombination loss across a Feshbach resonance in a
gas of ultracold 7Li atoms prepared in the absolute ground state and perform a
comparison with previously reported results of a different nuclear-spin state
[N. Gross et.al., Phys. Rev. Lett. 103 163202, (2009)]. We extend the
previously reported universality in three-body recombination loss across a
Feshbach resonance to the absolute ground state. We show that the positions and
widths of recombination minima and Efimov resonances are identical for both
states which indicates that the short-range physics is nuclear-spin
independent.Comment: 4 pages, 2 figure
Stable isochronal synchronization of mutually coupled chaotic lasers
The dynamics of two mutually coupled chaotic diode lasers are investigated
experimentally and numerically. By adding self feedback to each laser, stable
isochronal synchronization is established. This stability, which can be
achieved for symmetric operation, is essential for constructing an optical
public-channel cryptographic system. The experimental results on diode lasers
are well described by rate equations of coupled single mode lasers
Study of Efimov physics in two nuclear-spin sublevels of 7Li
Efimov physics in two nuclear-spin sublevels of bosonic lithium is studied
and it is shown that the positions and widths of recombination minima and
Efimov resonances are identical for both states within the experimental errors
which indicates that the short-range physics is nuclear-spin independent. We
also find that the Efimov features are universally related across Feshbach
resonances. These results crucially depend on careful mapping between the
scattering length and the applied magnetic field which we achieve by
characterization of the two broad Feshbach resonances in the different states
by means of rf-spectroscopy of weakly bound molecules. By fitting the binding
energies numerically with a coupled channels calculation we precisely determine
the absolute positions of the Feshbach resonances and the values of the singlet
and triplet scattering lengths.Comment: 15 pages, 7 figure
Observation of universality in ultracold 7Li three-body recombination
We report on experimental evidence of universality in ultracold 7Li atoms'
three-body recombination loss in the vicinity of a Feshbach resonance. We
observe a recombination minimum and an Efimov resonance in regions of positive
and negative scattering lengths, respectively, which are connected through the
pole of the Feshbach resonance. Both observed features lie deeply within the
range of validity of the universal theory and we find that the relations
between their properties, i.e. widths and locations, are in an excellent
agreement with the theoretical predictions.Comment: 5 pages, 2 figure
Public-channel cryptography based on mutual chaos pass filters
We study the mutual coupling of chaotic lasers and observe both
experimentally and in numeric simulations, that there exists a regime of
parameters for which two mutually coupled chaotic lasers establish isochronal
synchronization, while a third laser coupled unidirectionally to one of the
pair, does not synchronize. We then propose a cryptographic scheme, based on
the advantage of mutual-coupling over unidirectional coupling, where all the
parameters of the system are public knowledge. We numerically demonstrate that
in such a scheme the two communicating lasers can add a message signal
(compressed binary message) to the transmitted coupling signal, and recover the
message in both directions with high fidelity by using a mutual chaos pass
filter procedure. An attacker however, fails to recover an errorless message
even if he amplifies the coupling signal
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