1,669 research outputs found
Time- and frequency-domain polariton interference
We present experimental observations of interference between an atomic spin
coherence and an optical field in a {\Lambda}-type gradient echo memory. The
interference is mediated by a strong classical field that couples a weak probe
field to the atomic coherence through a resonant Raman transition. Interference
can be observed between a prepared spin coherence and another propagating
optical field, or between multiple {\Lambda} transitions driving a single spin
coherence. In principle, the interference in each scheme can yield a near unity
visibility.Comment: 11 pages, 5 figure
Spontaneous decay of artificial atoms in a multi-qubit system
We consider a one-dimensional chain of N equidistantly spaced noninteracting
qubits embedded in an open waveguide. In the frame of single-excitation
subspace, we systematically study the evolution of qubits amplitudes if the
only qubit in the chain was initially excited. We show that the temporal
dynamics of qubits amplitudes crucially depend on the value of kd, where k is
the wave vector, d is a distance between neighbor qubits. If kd is equal to an
integer multiple of , then the qubits are excited to a stationary level
which scales as SN^{-1}S. We show that in this case, it is the dark states
which prevent qubits from decaying to zero even though they do not contribute
to the output spectrum of photon emission. For other values of kd the
excitations of qubits have the form of damping oscillations, which represent
the vacuum Rabi oscillations in a multi-qubit system. In this case, the output
spectrum of photon radiation is defined by a subradiant state with the smallest
width.Comment: 22 pages, 12 figures, 17 reference
Gas Kinematics in the Magellanic-Type Galaxy NGC 7292
The paper presents results of studying the kinematics of the ionized gas in
the galaxy of the Large Magellanic Cloud type NGC 7292 obtained with the 2.5-m
telescope of the Caucasian Mountain Observatory (CMO SAI MSU) and the 6-m BTA
telescope of the Special Astrophysical Observatory (SAO RAS). Analysis of the
velocity fields of the ionized and neutral hydrogen showed that the kinematic
center of NGC 7292 located at the center of the bar, northwest of the
photometric center of the galaxy (the southeastern end of the bar) previously
taken as the center of NGC 7292. In addition to the circular rotation of the
gas, the radial motions associated with the bar play a significant role in the
kinematics of the disk. The observed perturbations of the gaseous-disk
kinematics induced by the ongoing star formation do not exceed those caused by
the bar. It is possible that part of the non-circular motions (at the
southeastern end of the bar which is the brightest HII region) may be related
to the effects of the capture of a dwarf companion or a gaseous cloud.Comment: Slightly edited version of the paper published in the Astrophysical
Bulletin. 10 pages, 8 figures, 1 tabl
NGC 7468: a galaxy with an inner polar disk
We present our spectroscopic observations of the galaxy NGC 7468 performed at
the 6-m Special Astrophysical Observatory telescope using the UAGS long-slit
spectrograph, the multipupil fiber spectrograph MPFS, and the scanning
Fabry-Perot interferometer (IFP). We found no significant deviations from the
circular rotation of the galactic disk in the velocity field in the regions of
brightness excess along the major axis of the galaxy (the putative polar ring).
Thus, these features are either tidal structures or weakly developed spiral
arms. However, we detected a gaseous disk at the center of the galaxy whose
rotation plane is almost perpendicular to the plane of the galactic disk. The
central collision of NGC 7468 with a gas-rich dwarf galaxy and their subsequent
merging seem to be responsible for the formation of this disk.Comment: 8 pages, 6 figures, accepted in Astronomy Letters, 2004, vol 30., N
9, p. 58
- …