Scientists build largest ever quantum key distribution network

Washington, July 2 (ANI): Researchers from across Europe have united to build the largest quantum key distribution (QKD) 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, Toshiba Research in the UK, Siemens, and many more have broken all previous records and taken another huge stride towards practical implementation of secure, quantum-encrypted communication networks.

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. Polten 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.

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

How scientists made fast quantum communication possible

Washington, April 30 (ANI): Researchers from Toshiba and Cambridge University’s Cavendish Laboratory have developed high speed detectors that are capable of receiving information with much higher key rates, thereby able to receive more information faster, in a technique known as quantum cryptography.

Carried in the journal paper, ‘Practical gigahertz quantum key distribution based on avalanche photodiodes’, the research details how quantum communication can be made possible without having to use cryogenic cooling and/or complicated optical setups, making it much more likely to become commercially viable soon.

One of the first practical applications to emerge from advances in the often baffling study of quantum mechanics, quantum cryptography has become the soon-to-be-reached gold standard 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 encryption.

The photons themselves are used to distribute keys that enable access to encrypted information, such as a confidential video 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 key information cannot be accessed by a third party without corrupting it beyond recovery and therefore making the act of hacking futile.

While other detectors can offer a key rate close to that reported in this journal paper, the present advance only relies on practical components for high speed photon detection, which has previously required either cryogenic cooling or highly technical optical setups, to make quantum key distribution much more user-friendly.

Using an attenuated (weakened) laser as a light source and a compact detector (semiconductor avalanche photodiodes), the researchers have introduced a decoy protocol for guarding against intruder attacks that would confuse with erroneous information all but the sophisticated, compact detector developed by the researchers.

According to the researchers, “With the present advances, we believe quantum key distribution is now practical for realizing high band-width information-theoretically secure communication.” (ANI)

Scientists demonstrate laser with controlled polarization

Washington, April 13 (ANI): A team of scientists has demonstrated, for the first time, lasers in which the direction of oscillation of the emitted radiation, known as polarization, can be designed and controlled at will.

The demonstration was made by applied scientists at the Harvard School of Engineering and Applied Sciences (SEAS), in collaboration with researchers from Hamamatsu Photonics in Hamamatsu City, Japan.

The innovation opens the door to a wide range of applications in photonics and communications.

“Polarization is one of the key features defining a laser beam. Controlling it represents an important new step towards beam engineering of lasers with unprecedented flexibility, tailored for specific applications,” explained graduate student Federico Capasso.

“The novelty of our approach is that instead of being conducted externally, which requires bulky and expensive optical components, manipulation of the beam polarization is achieved by directly integrating the polarizer on the laser facet,” he added.

“This compact solution is applicable to semiconductor lasers and other solid-state lasers, all the way from communication wavelengths to the mid-infrared and Terahertz spectrum,” he further added.

Light sources with a desirable polarization state are useful for a wide variety of applications.

For example, satellite communications use two orthogonal polarizations to double the capacity of the channel; circularly-polarized light sources are necessary to detect certain biomolecules; and laser sources with a variety of polarization states have relevance for quantum cryptography.

To achieve the results, the researchers sculpted a metallic structure, dubbed a plasmonic polarizer directly on the facet of a quantum cascade (QC) laser.

The QC laser emitted at a wavelength of ten microns (in the invisible part of the spectrum known as the mid-infrared where the atmosphere is transparent).

The team was able to control the state of polarization by generating both linearly polarized light along an arbitrary direction and circularly polarized light. (ANI)