46,954 research outputs found
Repeated Relativistic Ejections in GRS 1915+105
In 1994 February-August we observed with the VLA four ejection events of
radio emitting clouds from the high energy source GRS 1915+105. These events
are all consistent with anti-parallel ejections of twin pairs of clouds moving
away from the compact source at 0.92 of the speed of light and angles of
70 with respect to the line of sight. The flux ratios and time
evolution of the expelled clouds are consistent with actual motions of the
radiating matter rather than with the simple propagation of pulses in a medium
moving at slower velocities. The large kinetic power of the sudden, short, and
rather discontinuous ejections exceeds by more than an order of magnitude the
maximum steady photon luminosity of the source, suggesting that in GRS 1915+105
a radiation acceleration mechanism of the ejecta is unlikely. As in other
galactic and extragalactic radio sources, the decrease in flux density as a
function of angular separation from the central source shows a steepening with
distance. Additional ejection events have been observed in 1995 and 1997 and we
compare them with the 1994 events.Comment: 20 pages, 7 figures. To appear in The Astrophysical Journal, January
10, 1999 issu
A non-Markovian optical signature for detecting entanglement in coupled excitonic qubits
We identify an optical signature for detecting entanglement in experimental
nanostructure systems comprising coupled excitonic qubits. This signature owes
its strength to non-Markovian dynamical effects in the second-order temporal
coherence function of the emitted radiation. We calculate autocorrelation and
cross-correlation functions for both selective and collective light excitation,
and prove that the coherence properties of the emitted light do indeed carry
information about the entanglement of the initial multi-qubit state.
We also show that this signature can survive in the presence of a noisy
environment.Comment: 4 pages, 4 color figures. Minor changes. Accepted version to be
published in Europhysics Letter
Search for interactions between ejections of GRS 1915+105 and its environment
To unravel the effect of likely interactions between the energetic ejections
of the galactic superluminal source GRS 1915+105 and its surrounding
interstellar medium, we observed its environment. Two IRAS sources are
symmetrically placed with respect to GRS 1915+105, and are aligned with the
sub-arcsec ejections of this source.
We analyzed these two sources IRAS 19124+1106 and IRAS 19132+1035 through
near-infrared, millimeter and centimeter wavelengths. The evidence for these
regions being interaction zones seems inconclusive.Comment: 4 pages, 3 figures, to appear in Proceedings of X-ray Astronomy '999
- Stellar Endpoints, AGN and the Diffuse Background, 2000. G. Malaguti, G.
Palumbo & N. White (eds), Gordon & Breach (Singapore
Ultrafast optical signature of quantum superpositions in a nanostructure
We propose an unambiguous signature for detecting quantum superposition
states in a nanostructure, based on current ultrafast spectroscopy techniques.
The reliable generation of such superposition states via Hadamard-like quantum
gates is crucial for implementing solid-state based quantum information
schemes. The signature originates from a remarkably strong photon antibunching
effect which is enhanced by non-Markovian dynamics.Comment: 4 pages, 2 figures. Published in Phys. Rev. B (Rapid Communications
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