David Kirkpatrick

July 2, 2009

Moving toward quantum-encrypted communication networks

Very exciting news in milestone setting quantum-encrypted communications networking.

The release:

Researchers unite to distribute quantum keys

Researchers from across Europe have united to build the largest quantum key distribution network ever built. The efforts of 41 research and industrial organisations were realised as secure, quantum encrypted information was sent over an eight node, mesh network.

With an average link length of 20 to 30 kilometres, and the longest link being 83 kilometres, the researchers from organisations such as the AIT Austrian Institute of Technology (formerly Austrian Research Centers), id Quantique, Toshiba Research in the UK, Université de Genève, the University of Vienna, CNRS, Thales, LMU Munich, Siemens, and many more have broken all previous records and taken another huge stride towards practical implementation of secure, quantum-encrypted communication networks.

A journal paper, ‘The SECOQC Key Distribution Network in Vienna’, published as part of IOP Publishing’s New Journal of Physics‘ Focus Issue on ‘Quantum Cryptography: Theory and Practice’, illustrates the operation of the network and gives an initial estimate for transmission capacity (the maximum amount of keys that can be exchanged on a quantum key distribution, QKD, network).

Undertaken in late 2008, using the company internal glass fibre ring of Siemens and 4 of its dependencies across Vienna plus a repeater station, near St. Pölten in Lower Austria, the QKD demonstration involved secure telephone communication and video-conference as well as a rerouting experiment which demonstrated the functionality of the SEcure COmmunication network based on Quantum Cryptography (SECOQC).

One of the first practical applications to emerge from advances in the sometimes baffling study of quantum mechanics, quantum cryptography has become a soon-to-be reached benchmark in secure communications.

Quantum mechanics describes the fundamental nature of matter at the atomic level and offers very intriguing, often counter-intuitive, explanations to help us understand the building blocks that construct the world around us. Quantum cryptography uses the quantum mechanical behaviour of photons, the fundamental particles of light, to enable highly secure transmission of data beyond that achievable by classical methods.

The photons themselves are used to distribute cryptographic key to access encrypted information, such as a highly sensitive transaction file that, say, a bank wishes to keep completely confidential, which can be sent along practical communication lines, made of fibre optics. Quantum indeterminacy, the quantum mechanics dictum which states that measuring an unknown quantum state will change it, means that the information cannot be accessed by a third party without corrupting it beyond recovery and therefore making the act of hacking futile.

The researchers write, “In our paper we have put forward, for the first time, a systematic design that allows unrestricted scalability and interoperability of QKD technologies.”



April 23, 2009

Nanotech heading toward artificial noses

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 11:04 pm

First, a word of caution — get ready for a nanocentric release dump. I haven’t done one in a while so more will follow this post.

Now to the news — the idea of an artificial nose is a good thing because they can be utilized to detect various substances. A nanotech-driven artificial nose might even “sniff out” a single molecule of the target.

The release from today:

Scientists moving closer to ‘artificial noses’

More than one nanostring to their bow

These days, chemical analysts are expected to track down even single molecules. To do this highly sensitive detective work, nano researchers have developed minute strings that resonate in characteristic fashion. If a molecule docks onto one of the strings, then it becomes heavier, and its oscillations become measurably slower. Until recently, however, such “nano-electromechanical systems”, or NEMS, have been short of practical applications. Physicists at LMU Munich have now made a breakthrough in this field: They have constructed a system of nanostrings made of non-conducting material, where each string can be electrically excited separately. Thousands of these strings can be produced on a small chip. One of the devices that could be created with this system is a highly sensitive “artificial nose” that detects various molecules – pollutants for example – individually. These new NEMS could also be used in a multitude of other applications – acting as tiny pulse generators in mobile phone clocks, for example.

Quick, certain and cheap detection of single molecules is a task that chemical analysts are now expected to perform. Luckily, there is a method they can employ for this, which uses nanotechnology: Specifically, they use “nano-electromechanical systems”, or NEMS. These systems involve strings with diameters of the order of 100 nanometers – a ten-thousandth of a millimeter or a 1/500 of a human hair – which can be excited to resonate in a characteristic fashion. If these strings are coated with the right kind of chemicals, then molecules will dock onto them. More specifically: only one kind of molecule can dock onto each string. When a molecule docks onto a string, the string becomes heavier and its oscillation slows down a tiny bit. “By measuring the period of oscillation, we could therefore detect chemical substances with molecular precision,” explains Quirin Unterreithmeier, first author of the study. “Ideally, you would have several thousand strings sitting on a chip the size of a fingernail, each one for highly specifically recognizing a single molecule – so you could build an extremely sensitive ‘artificial nose’, for example.”

Until recently, however, getting such systems to work has proven technically difficult; one problem being to produce and measure the oscillations. While the nanostrings can be made to oscillate by magnetomechanical, piezoelectric or electrothermal excitement, this only works if the nanostrings are made of metal, or are at least metal-coated, which in turn greatly dampens the oscillations, preventing sensitive measurement. That hardly allows the detection of a single molecule. It also makes it harder to distinguish the different signals from differently oscillating strings.

The newly developed method now avoids these difficulties. Quirin Unterreithmeier, Dr. Eva Weig and Professor Jörg Kotthaus of the Center for NanoScience (CeNS), the Faculty of Physics of LMU Munich and the cluster of excellence “Nanosystems Initiative Munich (NIM)” have constructed an NEMS in which the nanostrings are excited individually by dielectric interaction – the same phenomenon that makes hair stand on end in winter. Following this physical principle, the nanostrings, which are made of electrically non-conducting silicon nitride, are excited to resonate when exposed to an oscillating inhomogeneous electric field, and their vibration then measured.

The alternating electric field required for this stimulation was produced between two gold electrodes right up close to the string. The oscillations were measured by two other electrodes. “We created this setup using etching techniques,” reports Weig. “But this was easily done – even repeated ten thousand times on a chip. The only thing to do now is to make sure the strings can be individually addressed by a suitable circuit.” All in all, this ought to be a technically easy exercise – but one that will allow a breakthrough in chemical analysis. Yet there are even more applications that can be seen beyond this “artificial nose”. Among other things, the nanostrings could be employed as the pulse generators in mobile phone clocks, for example. These novel resonators could even be used as ultra-sharp electrical signal filters in metrological systems.




The study is a project of the cluster of excellence “Nanosystems Initiative Munich” (NIM), which has its sights set on developing, researching and bringing into operation functional nanosystems for application in information processing and life sciences. (NIM/suwe)

Print material is available at: www.nano-initiative-munich.de/press/press-material

“Universal transduction scheme for nanomechanical systems based on dielectric forces”,
Quirin P. Unterreithmeier, Eva M. Weig, Jörg P. Kotthaus
Nature, 23 April 2009