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Nanotube
quantum dot doubles up
NANOTECH JAN 04
Researchers at Harvard University, US, have made a nanotube double
quantum dot by gating a carbon nanotube in a number of places. The
strength of the tunnel coupling between the dots was tunable, a feature which
means that the device could have applications in quantum computing.
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Fermionic
condensate makes its debut
PHYSICSWEB JAN 04
Physicists in the US have created an elusive state of matter known as a "fermionic
condensate" for the first time. Deborah Jin, Markus Greiner and Cindy Regal
and the JILA laboratory in Boulder, Colorado, made the condensate from pairs of
ultracold fermionic atoms.
(arxiv.org/abs/cond-mat/0401554; Phys. Rev. Lett to be published).
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A
quantum leap in codes for secure transmissions
Banks,
intelligence agencies and governments may soon be using an uncrackable method of
transporting their data. According to Jennifer L Schenker, in an article written
for the International Herald Tribune on 28/01/2004, scientists in Europe, Asia
and the United States say they are close to producing a commercial product.
This
abstract has been taken from an original article written by Jennifer L. Schenker
for the International Herald Tribune on 01/28/2004. Copyright (c) 2004 Bell & Howell Information and Learning
Company. All rights reserved.
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Condensate
research heats up
PHYSICSWEB JAN 04
Physicists have moved a step
closer to making a Bose-Einstein condensate in a semiconductor for the first
time. Researchers at the University of California at Berkeley, the Lawrence
Berkeley National Laboratory and the University of California at Santa Barbara
have demonstrated the existence of distinct regions of confined degenerate
excitons in a semiconducting material (C W Lai et al. 2004 Science 303 503). An
exciton is the bound state of a negative electron and a positive
"hole".
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Opportunity to
Tender "Verification of Quantum Mechanics & New Applications of Quantum
Technologies & Methods in Space"
ESA (European Space
Agency) extend invitation to Tender
Although this invitation does not directly address quantum
information processing, some of our members and associates may
be interested. The attached PDF files contain the cover
letter, the Statement of Work and some supporting
documentation. The title, above, links to the website.
Cover letter
Statement of Work
Supporting documentation
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Photonic
crystals boost semiconductor lasers
PHYSICSWEB OCT 03
Physicists have made a new type of laser by combining a
quantum cascade laser with a photonic crystal. Raffaele
Colombelli of Bell Labs in the US and colleagues say that
their novel proof-of-concept device could find use in sensing
applications and funamental research in optics (R. Colombelli
et al 2003 Sciencexpress 1090561).
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Schrödinger's
cat comes closer
NATURE OCT 03
The physicist Erwin Schrödinger famously
said that quantum theory would allow the existence of a cat
that was simultaneously living and dead. Scientists are resigned
to atom-sized entities being capable of such feats but they
generally assume that at larger scales decoherence intervenes,
stamping out quantum weirdness and fixing everyday objects
to a single definite location. William Marshall et al, of
the University of Oxford, outline
a scheme for evading decoherence to achieve a quantum superpostion
of states in an object with around a hundred trillion atoms
- about a billion times larger than anything demonstrated
previously.
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Magnetic
logic devices move closer
PHYSICSWEB OCT 03
In most computers bits of data are stored in one place and processed
in another. Now German physicists have proposed a new magnetic
approach to computing in which the same element can store and
process data. Andreas Ney and colleagues at the Paul Drude Institute
in Berlin say that their "programmable logic element"
could, in principle, operate as any one of four different logic
operations - AND, OR, NAND or NOR gates - and lead to increased
computational efficiency (A Ney et al. 2003 Nature 425 485).
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Quantum-dot
computing
PHYSICSWEB OCT 03
A quantum computer would put the latest PC to shame. Not only
would such a device be faster than a conventional computer,
but by exploiting the quantum-mechanical principle of superposition
it could change the way we think about information processing.
However, two key goals need to be met before a quantum computer
becomes reality. The first is to be able to control the state
of a single quantum bit (or "qubit") and the second
is to build a two-qubit gate that can produce "entanglement"
between qubit states.
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Photonic
band gaps deliver the goods
PHYSICSWEB OCT 03
It is hard to imagine a better way of transporting light than
using an optical fibre. By surrounding a transparent fibre core
with a second material that has a lower refractive index, light
in the inner core is trapped by total internal reflection. In
silica-based optical fibres, light can propagate in this way
with low losses over global distances.
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First
light for one-atom laser
PHYSICSWEB SEPT 03
Physicists in the US have built a laser with a single atom for
the first time. Jeff Kimble and colleagues at the California
Institute of Technology made the device by trapping a cold caesium
atom in an optical cavity. The one-atom laser produces nonclassical
light that could have applications in quantum information technology
(J McKeever et al. 2003 Nature 425 268).
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Quantum
logic gate lights up
PHYSICSWEB AUG03
Physicists in the US have taken another important step towards
making a quantum computer. Duncan Steel of the University of
Michigan and co-workers have created a logic gate using two
electron-hole pairs - also known as "excitons" - in
a quantum dot (X Li et al. 2003 Science 301
809).
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Squeezed
light breaks quantum barrier
PHYSICSWEB AUG03
Physicists have made a new type of ultra-precise laser pointer
by "squeezing" a beam in two directions. Hans Bachor
and colleagues at the Australian National University in Canberra
and the Université Pierre et Marie Curie in Paris are
able to position the beam with a precision of
1.6 Angstroms. This is almost 1.5 times better than the theoretical
limit for a conventional laser. The technique could be used
to improve the performance of a range of optical instruments
and also in imaging applications in physics and biology (N Treps
et al. 2003 Science 301 940).
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