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2Physics Quote:
"The exchange character of identical particles plays an important role in physics. For bosons, such an exchange leaves their quantum state the same, while a single exchange between two fermions gives a minus sign multiplying their wave function. A single exchange between two Abelian anyons gives rise to a phase factor that can be different than 1 or -1, that corresponds to bosons or fermions, respectively. More exotic exchanging character are possible, namely non-Abelian anyons. These particles have their quantum state change more dramatically, when an exchange between them takes place, to a possibly different state." -- Jin-Shi Xu, Kai Sun, Yong-Jian Han, Chuan-Feng Li, Jiannis K. Pachos, Guang-Can Guo
(Read Full Article: "Experimental Simulation of the Exchange of Majorana Zero Modes"
)

Sunday, July 31, 2005

Quarks on a chip

Quarks are considered to be fundamental building blocks of matter and
are bound together inside subatomic particles by the 'strong nuclear
force' (see our past posting), which is weak when the quarks are close,
but increases steadily as they move apart, making it impossible to isolate
a single quark.

Quarks are the inner constituents of 99.9% of ordinary matter; yet it is
impossible to examine a single quark in the laboratory. Consequently,
some of their basic properties are not known, such as their precise masses
or why they exist in 6 different types.

In order to understand Quarks, the theory describing the strong nuclear
force, called Quantum Chromodynamics (QCD), has to be simulated on
huge computers. Particle physicists are embarking on a new attempt to
resolve the mysteries of quarks using 3 purpose-designed computers
that employ QCD-on-a-chip, or QCDOC, technology.

The first of the three computers is located at the University of Edinburgh
(UK), for use by the UK Quantum Chromodynamics (UKQCD)
collaboration of scientists from 7 British universities. The 2nd is at the
RIKEN Brookhaven Research Center in Brookhaven National Laboratory
in the USA. The 3rd, part of the US Department of Energy's programme
in high energy and nuclear physics, is also at Brookhaven.

A little slower than a PC's microprocessor, the QCDOC chip was designed
to consume a 10th of the electrical power, so that tens of thousands of
them could be put into a single machine. Each machine operates at a speed
of 10 Teraflops, or 10 trillion (i.e. million million) floating point operations
per second. By comparison, a regular desktop computer operates at a few
Gigaflops (a thousand million floating point operations per second), while
IBM's BlueGene, a close relative of QCDOC and the fastest computer in
the world, operates at more than 100 Teraflops.

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