2003 Articles

 

Molecular dots rise for information storage

PHYSICSWEB JAN 03
Researchers have made a new molecular device that could store up to 100 gigabits of data per square inch. Massimiliano Cavallini of the CNR-ISMN in Bologna in Italy and colleagues at Bologna and Edinburgh universities used molecules called "rotaxanes" to make the device. The special
structure of these molecules suggest that they could be used as switchable components for artificial machines
(M.Cavallini et al. Science 2003 299 531)
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Bad news for code breakers

PHYSICSWEB JAN 03
By encoding messages using the quantum states of photons, quantum cryptography offers the prospect of completely secure data transmission. However, physicists have found it difficult to make the single-photon sources needed in most variants of quantum cryptography. Now, Frédéric Grosshans of the Institute of Optics in Orsay, France, and colleagues have shown experimentally how to encode data using pulses containing several hundred photons. Their technique remains secure even when the pulses are degraded during transmission.
(F Grosshans et al. 2003 Nature 421 238).
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Nanowire lasers go electric

PHYSICSWEB JAN 03
Scientists have shown for the first time that a single-crystal nanowire can act as an efficient electrically driven laser. Charles Lieber and colleagues at Harvard University believe that such nanoscale lasers could be made to emit over wide range of wavelengths for a variety of
applications, including telecommunications and high density data storage.
(X Duan et al. 2003 Nature 421 241).
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  DNA computer makes its own energy

NANOTECHWEB FEB 03  
Scientists from the Weizmann Institute of Science in Israel have come up with a DNA computing device that provides its own energy. The device uses DNA molecules as both input data and as a fuel source.
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Single molecule switches for less

NANOTECHWEB FEB 03
Switches made from single molecules could greatly reduce the power consumed by electronic devices, compared to present-day solid-state integrated circuits. Ernst Meyer, Christian Joachim and colleagues from the University of Basle, IBM Zurich and the CEMES-CNRS Lab in Toulouse have now created the lowest energy single-molecule switch to date.
See
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Photonic circuits move a step closer

PHYSICSWEB FEB 03
The use of light rather than electrons to carry information is of increasing importance in high-speed communication. A major challenge in "photonics" is to combine components that can manipulate light with traditional chips. Now, Kerry Vahala and co-workers at the California Institute of Technology have fabricated microresonators-on-a-chip that have "Q" values ten thousand times larger than existing devices (D K Armani et al. 2003 Nature 421 925)
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  DNA strings along metal atoms

NANOTECHWEB FEB 03
Researchers from the University of Tokyo and the Institute for Molecular Science in Japan have used DNA to assemble strings of up to five copper ions. The technique could have applications in producing molecular magnets and wires.
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Nanoporous magnet sucks up solvents

NANOTECHWEB FEB 03
Researchers have created a nanoporous molecular magnet with a metal-organic open-framework structure. The scientists, from the Institut de Ciència de Materials de Barcelona in Spain, the University of Innsbruck in Austria, Barcelona University in Spain and the CNR-Institute for the Study of Nanostructured Materials in Italy, believe that the material could have applications as a new type of magnetic sensor for molecules.
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  Diatomists shell out on nanotechnology

NANOTECHWEB FEB 03
It's unlikely that many nanotechnologists are familiar with diatoms - a group of single-celled shelled algae - but that could change following a world-first conference on diatom nanotechnology that's set to take place in the US in October. Liz Kalaugher spoke to conference organizer Richard Gordon of the University of Manitoba, Canada, to find out more.
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Superconductor transistor breaks records

PHYSICSWEB FEB 03
Researchers in Finland have built a new type of superconducting amplifier, which has the highest current and power gains observed in such a device to date. Pertti Hakonen and colleagues at the Helsinki University of Technology and VTT Information Technology believe that the device could be used in low-temperature applications, including readout elements for quantum computers (J Delahaye et al. 2003 Science 299 1045)
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  Qubits are on solid ground

PHYSICSWEB FEB 03
Physicists in Japan, the Netherlands and the US have taken important steps towards building a quantum computer. Jaw-Shen Tsai, Yasunobu Nakamura and colleagues at the RIKEN and NEC laboratories in Japan and the State University of New York at Stony Brook have "entangled" two
quantum bits or "qubits" in a solid-state device for the first time (YA Pashkin et al. 2003 Nature 421 823). Meanwhile, Irenel Chiorescu and co-workers at the Delft University of Technology, working with Nakamura, have demonstrated a new type of superconducting qubit (I Chiorescu et al.
2003 Sciencexpress 1081045)
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  Nanowires approach the quantum realm

PHYSICSWEB FEB 03 
Scientists at the City University of Hong Kong have fabricated the smallest silicon nanowires ever. Shuit-Tong Lee and colleagues believe that such wires - which have diameters approaching 1 nanometre - could be used to make UV light-emitting diodes, transistors and lasers (D D Ma et
al. 2003 Sciencexpress to be published)
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Single molecule switches for less

PHYSICSWEB FEB 03
Switches made from single molecules could greatly reduce the power consumed by electronic devices, compared to present-day solid-state integrated circuits. Ernst Meyer and Christian Joachim and colleagues from the University of Basle, IBM Zurich and the CEMES-CNRS Lab in Toulouse have now created the lowest energy single-molecule switch to date. It requires only 47 zeptojoules - 47 x 10-21 joules or 0.3 eV - to operate, which is 10 000 times less than the power needed in the
transistor switches currently used in high-speed computers (C Loppacher et al. 2003 Phys. Rev. Lett. 90 066107)
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Teleportation moves on

PHYSICSWEB FEB 03
When physicists teleported photons for the first time in 1997 they had to destroy the photons to be sure that the teleportation had been successful. Now a team at the University of Vienna has managed to teleport photons without destroying them. Jian-Wei Pan and colleagues believe that their method could be the next step towards long-distance quantum communication
(J-W Pan et al. 2003 Nature 421 721).
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Novel photomasks make 3-D microstructures

PHYSICSWEB FEB 03
Scientists in the US have used a new technique to make complex, three-dimensional microstructures. Albert Folch and colleagues at the University of Washington in Seattle believe that their method could provide an inexpensive alternative to the traditional photolithographic
approaches currently used to fabricate computer chips and other miniature structures
(C Chen et al. 2003 Proc. Nat. Acad. Sci. to be published)
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Trapped ions make logic gates

PHYSICSWEB MAR 03
Quantum computing has moved another step forward as two independent research groups report the creation of logic gates using pairs of trapped ions. The scientists - based in the US and Austria - have demonstrated new techniques that involve the quantum control of "entangled" ions. The
researchers believe that these logic gates could be scaled up to include many qubits in a large, workable quantum computer (D Leibfried et al. 2003 Nature 422 412 and F Schmidt-Kaler et al. 2003 Nature 422 408).
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  Silver nanoclusters make logic gates

PHYSICSWEB MAR 03
Researchers at the Georgia Institute of Technology have performed logic operations with a novel optoelectronic device made of silver nanoclusters. The device built by Robert Dickson and Tae-Hee Lee operates on electronic inputs and produces an optical output that can be read
without electrical contacts (T-H Lee and R M Dickson 2003 Proc. Nat. Acad. Sci. to be published)
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Quantum effect improves tomography

PHYSICSWEB AUG 03
Physicists at Boston University in the US have improved the axial
resolution of optical coherence tomography (OCT) by a factor of five.
Malvin Teich, Bahaa Saleh and colleagues used a two-photon source in what
they claim is the first experimental demonstration of quantum OCT (M B
Nasr et al. 2003 Phys. Rev. Lett. 91 083601).
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Entanglement goes macroscopic

PHYSICSWEB SEP 03
Quantum entanglement is a phenomenon usually associated with the
microscopic world. Now, however, physicists from the Universities of
Chicago and Wisconsin in the US and University College London have seen
its effects in the bulk properties of a magnetic material for the first
time. The researchers believe that their work has implications both for
understanding quantum magnetism and in building quantum computers - where
entanglement is the key to the increased power of such devices (S Ghosh
et al. 2003 2003 Nature 425 48).
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Biomolecule behaves like a wave

PHYSICSWEB SEP 03
Physicists at the University of Vienna in Austria have observed wave-particle duality in a biomolecule for the first time. The team also reports observing wave-like behaviour in the most massive molecule yet- a fluorinated 'buckyball'. It is twice as large as the previously biggest molecule known to exhibit quantum wave-like behaviour ( L Hackermüller et al. 2003 Phys. Rev. Lett. 91 090408).
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Nanotubes make miniature gas sensors

PHYSICSWEB JUL 03
Researchers in the US have used carbon nanotubes to make a miniature gas ionization sensor. Pulickel Ajayan and colleagues at the Rensselaer Polytechnic Institute in New York state say that their detector offers a low-cost, more practical alternative to conventional ionization sensors
(A Modi et al. 2003 Nature 424 171).
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Fast and slow light made easy

PHYSICSWEB JUL 03
Physicists have created "slow" and "fast" light in a crystal at room temperature for the first time. The team at the University of Rochester in the US used an `alexandrite' crystal to reduce the speed of light to just 91 metres per second, and also to make a laser pulse travel faster than the speed of light. Previously these effects - which are not in conflict with special relativity - had only been observed at cryogenic temperatures or in complicated experimental set-ups. The new technique
could be used for applications such as optical data storage, optical memories and quantum information devices (M Bigelow et al. 2003 Science 301 200).
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A new way to flip bits

PHYSICSWEB JUL 03
Physicists in Japan have shown that electric fields could be used to improve the performance of magnetic data storage devices. Hideo Ohno and colleagues at Tohoku University demonstrated that the magnetic field needed to reverse the magnetization in a storage bit can be reduced by
applying an electric field. By making it easier to `flip' the magnetization of a material, the new method could have applications in ultrahigh-density information storage devices (D Chiba et al. 2003
Sciencexpress 1086608).
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Room-temperature single-electron devices made easier

PHYSICSWEB JUN 03
Physicists at Cambridge University in the UK and the Japan Science & Technology Corporation in Tokyo have exploited a "natural" system of tunnel barriers in nanocrystalline silicon to make a single-electron transistor that operates at room temperature. The researchers say that the technique used to fabricate the transistor is compatible with existing silicon technology and has "considerable processing advantages" over the techniques previously used to make similar devices (Y T Tan et
al. 2003 J. Appl. Phys. 94 633).
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Fermi gas atoms form supercool molecules

PHYSICSWEB JUL 03
Researchers in the US have made ultracold molecules from a gas of fermionic atoms for the first time. Deborah Jin of the National Institute of Standards and Technology in Boulder and colleagues at the JILA laboratory, also in Boulder, have created more than a quarter of a million molecules in their experiment. The result is an important step towards making molecular Bose-Einstein condensates and an exotic fermionic superfluid (C Regal et al. 2003 Nature 424 47).
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Entanglement bridges the Danube

PHYSICSWEB JUL 03
Physicists have broken another distance record for demonstrating the quantum properties of light. Markus Aspelmeyer and colleagues at the University of Vienna in Austria have shown that it is possible for two photons to travel a total of 600 metres through free space and still remain "entangled" (Science to be published). The previous record for entanglement in free space was a few metres).
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Carbon nanotubes light up

PHYSICSWEB MAY 03
Scientists at IBM Research in the US have obtained light from a carbon nanotube by a passing current through it. Phaedon Avouris and co-workers say that the device could be used to fabricate ultrasmall optoelectronics devices for applications in high-speed communications (J A Misewich et
al. 2003 Science 300 783).
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  Entanglement reaches new lengths

PHYSICSWEB MAY 03
A successful solid-state quantum computer will have to `entangle' quantum bits - or `qubits' - over macroscopic distances. However, entanglement in solid-state systems has only been observed on the micrometre scale so far. Now, Andrew Berkley and colleagues from the University of Maryland have entangled two solid-state superconducting qubits over a distance of 0.7 mm - a thousand times greater than ever before (A J Berkley et al. 2003 Sciencexpress 1084528 ).
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Alchemy with light shocks physicists

NEW SCIENTIST MAY 03
 Claims of "unexpected and stunning new physical phenomena" are rare in the abstract of a reputable scientific paper. But the latest report by photonics crystal pioneer John Joannopoulos and his group at MIT, soon to be published in Physical Review Letters, does not disappoint.
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  Cryptography breaks 100 km barrier

NEW SCIENTIST MAY 03
Researchers in the UK have broken the distance record for quantum cryptography, the optical technique that enables `unhackable' communication along an optical fibre. Andrew Shields and colleagues from Toshiba Research Europe, UK, revealed their record-breaking link, which
reaches over 100 km, at the Conference on Lasers and Electro-Optics (CLEO) in Baltimore, US.
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  Microscope sketches quantum circuits

PHYSICSWEB AUG03
Physicists at Cambridge University in the UK have developed a new way to make quantum electronic devices using an atomic force microscope. The technique, known as erasable electrostatic lithography, allows researchers to create and change quantum devices and circuits during an
experiment - a feat that was hitherto impossible. Erasable lithography could be used in experiments to study quantum phenomena and may also provide a route to the fabrication of a solid-state quantum computer (R Crook et al. 2003 Nature 424 751).

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  Molecules build a bridge to spintronics

PHYSICSWEB AUG 03
The prospect of a new generation of devices that harness the spin of electrons has moved closer following a recent experiment in the US. Min Ouyang and David Awschalom of the University of California at Santa Barbara have transferred electron spins across molecular `bridges' between quantum dots for the first time. Even better, the pair found that they could transfer the spins most effectively at room temperature (M Ouyang and D Awschalom 2003 Sciencexpress 1086963).

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