Science > Physics > PHYSICS NEWS UPDATE -- Number 722 March 3, 2005 by Phillip F. Schewe,Ben Stein
| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
03 Mar 2005 01:57:57 PM |
| Object: |
PHYSICS NEWS UPDATE -- Number 722 March 3, 2005 by Phillip F. Schewe,Ben Stein |
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 722 March 3, 2005 by Phillip F. Schewe, Ben Stein
240 ELECTRONS SET IN MOTION. A soccerball-shaped carbon-60
molecule, possessing a mobile team of up to about 240 valence
electrons holding the structure together, is sort of halfway between
being a molecule and a solid. To explore how all those electrons
can move as an ensemble, a team of scientists working at the
Advanced Light Source synchrotron radiation lab in Berkeley, turned
the C-60 molecules into a beam (by first ionizing them) and then
shot ultraviolet photons at them. When a photon absorbed, the
energy can be converted into a collective movement of the electrons
referred to as a plasmon. Previously a 20-electron-volt "surface
plasmon" was observed: the absorption of the UV energy resulted in a
systematic oscillation of the ensemble of electrons visualized as a
thin sphere of electric charge. Now a new experiment has found
evidence of a second resonance at an energy of 40 eV. This second
type of collective excitation is considered a "volume plasmon" since
the shape of the collective electron ensemble is thought to be
oscillating with respect to the center of the molecule (see figure
at http://www.aip.org/png/2005/230.htm). The collaboration consists
of physicists from the University of Nevada, Reno (Ronald Phaneuf,
775-784-6818, phaneuf@unr.edu), Lawrence Berkeley National Lab,
Justus-Liebig-University (Giessen, Germany), and the Max Planck
Institute (Dresden). (Scully et al., Physical Review Letters, 18
February 2005)
FIRST EVIDENCE FOR ENTANGLEMENT OF THREE MACROSCOPIC OBJECTS has
been seen in a superconducting circuit built at the University of
Maryland. By examining an electrical circuit operating at
temperatures near absolute zero, the researchers have found new
evidence that the laws of quantum mechanics apply not just to
microscopic particles such as atoms and electrons, but also to large
electronic devices called superconducting quantum bits (qubits).
While researchers have previously created superconducting qubits,
and other groups have entangled two macroscopic objects (Update
558), this research is the first to observe the quantum interaction
of three macroscopic
components: a niobium inductor-capacitor (LC) circuit plus a pair of
Josephson junctions, each a sandwich of two superconductors
separated by an insulator. Remarkably, all three macroscopic
devices seem to act, when cold enough, like huge atoms. The LC
circuit coupled the Josephson junctions in such a way as to transfer
quantized oscillations of current in one junction to the other
junction. The LC circuit was more than a simple connector; its
condition depended upon the two Josephson junctions in a way defined
by the laws of quantum mechanics. The researchers obtained evidence
of the entanglement indirectly, through the use of microwave pulses
that probed the Josephson junctions; future experiments will seek to
directly control the junctions and obtain evidence more directly.
Superconducting circuits such as this one provide a promising route
towards a practical quantum computer, which would require the
entanglement of many qubits. Scaling up superconducting devices to
many-qubit systems should be possible once single superconducting
qubits are perfected, according to team member Frederick Strauch,
(now at NIST, 301-975-5159, Frederick.Strauch@nist.gov). The
challenge will be to fabricate sufficiently high-quality circuits so
that the superconducting qubits achieve the very low noise levels
necessary for quantum computing. (Xu et al.,
Physical Review Letters, 21 January 2005)
X-RAY THUNDERBOLT. Scientists have long suspected that lightning
might generate x rays. However, until recently the observation of
such x-rays has remained elusive, largely owing to the unpredictable
nature of lightning. In the last few years a series of experiments
by Joseph Dwyer and his colleagues at the Florida Institute of
Technology and the University of Florida has shown that lightning
indeed emits large bursts of x rays with energies up to about 250
keV (about twice that of a chest x ray). These x rays are mostly
produced not by the bright return strokes, but by the leaders that
precede the stroke, as they propagate from the cloud to the ground.
Now, Dwyer and his colleagues have discovered that these bursts of x
rays are produced at the precise moment that the lightning steps
forward along its jagged path. For unknown reasons, lightning does
not travel to the ground in a continuous manner, but instead
traverses the distance in a series of discrete steps. It is this
stepping process that gives lightning its jagged, sometimes forked,
appearance, and Dwyer has now shown that this same stepping process
also makes x rays. The x rays are likely produced by strong
electric fields that accelerate electrons to close to the speed
of light. These so-called runaway electrons collide with air
producing bremsstrahlung ("braking radiation" in German) x-rays.
Dwyer says that higher energy gamma rays are also emitted sometimes,
but that these seem to come from the thunderstorm cloud itself and
not from the lightning stroke. (Dwyer et al., Geophysical Review
Letters, 16 January 2005.)
***********
PHYSICS NEWS UPDATE is a digest of physics news items arising
from physics meetings, physics journals, newspapers and
magazines, and other news sources. It is provided free of charge
as a way of broadly disseminating information about physics and
physicists. For that reason, you are free to post it, if you like,
where others can read it, providing only that you credit AIP.
Physics News Update appears approximately once a week.
.
|
|
| User: "pctech" |
|
| Title: Re: PHYSICS NEWS UPDATE -- Number 722 March 3, 2005 by Phillip F. Schewe, Ben Stein |
03 Mar 2005 10:33:45 PM |
|
|
I'm trying to get laptop in time for church camp summer job. Please
help if you can by using my referal link:
http://www.pctech4free.com/default.aspx?ref=59054
Thanks in advance.
.
|
|
|
|
|
Related Articles |
PHYSICS NEWS UPDATE -- Number 724 March 25, 2005 by Phillip F.Schewe, Ben Stein
PHYSICS NEWS UPDATE -- Number 769 March 17, 2006 by Phillip F.Schewe, Ben Stein, and Davide Castelvecchi
PHYSICS NEWS UPDATE -- Number 814 March 9, 2007 by Phillip F. Schewe,Ben Stein
PHYSICS NEWS UPDATE -- Number 817 March 29, 2007 by Phillip F. Schewe,Ben Stein
PHYSICS NEWS UPDATE -- Number 771 March 29, 2006 by Phillip F.Schewe, Ben Stein, and Davide Castelvecchi
PHYSICS NEWS UPDATE -- Number 768 March 9, 2006 by Phillip F.Schewe, Ben Stein, and Davide Castelvecchi
PHYSICS NEWS UPDATE -- Number 816 March 23, 2007 by Phillip F.Schewe, Ben Stein
PHYSICS NEWS UPDATE -- Number 723 March 15, 2005 by Phillip F. Schewe,Ben Stein
| PHYSICS NEWS UPDATE -- Number 770 March 23, 2006 by Phillip F.Schewe, Ben Stein
PHYSICS NEWS UPDATE -- Number 815 March 16, 2007 by Phillip F.Schewe, Ben Stein
Physics News Update - Number 675, March 3, 2004
Physics News Update - Number 652, September 4, 2003
Physics News Update Number 653, September 12, 2003
PHYSICS NEWS UPDATE -- Number 654 September 17, 2003
Physics News Update -- Number 655, September 26, 2003
|
|
|
