Team finds the 'key' to quantum network solution

May 25, 2015
Credit: University of York

Scientists at the University of York's Centre for Quantum Technology have made an important step in establishing scalable and secure high rate quantum networks.

Working with colleagues at the Technical University of Denmark (DTU), Massachusetts Institute of Technology (MIT), and the University of Toronto, they have developed a protocol to achieve key-rates at metropolitan distances at three orders-of-magnitude higher than previously.

Standard protocols of Quantum Key Distribution (QKD) exploit random sequences of (qubits) to distribute secret keys in a completely secure fashion. Once these keys are shared by two remote parties, they can communicate confidentially by encrypting and decrypting binary messages. The security of the scheme relies on one of the most fundamental laws of , the uncertainty principle.

Today's classical communications by email or phone are vulnerable to eavesdroppers but quantum communications based on single particle levels (photons) can easily detect eavesdroppers because they invariably disrupt or perturb a quantum signal. By making quantum measurements, two remote parties can estimate how much information an eavesdropper is stealing from the channel and can apply suitable protocols of privacy amplification to negate the effects of the information loss.

However, the problem with QKD protocols based on simple quantum systems, such as single-photon qubits, is their low key-rate, despite their effectiveness in working over long distances. This makes them unsuitable for adaptation for use in metropolitan networks.

The team, led by Dr Stefano Pirandola, of the Department of Computer Science at York, overcame this problem, both theoretically and experimentally, using continuous-variable . These allow the parallel transmission of many qubits of information while retaining the quantum capability of detecting and defeating eavesdroppers. The research is published in Nature Photonics.

Dr Pirandola said: "You want a high rate and a fast connection particularly for systems that serve a metropolitan area. You have to transmit a lot of information in the fastest possible way; essentially you need a quantum equivalent of broadband.

"Continuous-variable systems can use many more photons but are still quantum based. Our system reaches extremely high speeds by three orders of magnitude higher than ever before over a distance of 25 kilometres. Its effectiveness above that distance decreases rapidly however.

"Nevertheless, our protocol could be used to build high-rate where devices securely connect to nearby access points or proxy servers."

Explore further: Doing more with less: Steering a quantum path to improved internet security

More information: High-rate measurement-device-independent quantum cryptography, Nature Photonics, DOI: 10.1038/nphoton.2015.83

Related Stories

New research signals big future for quantum radar

February 26, 2015

A prototype quantum radar that has the potential to detect objects which are invisible to conventional systems has been developed by an international research team led by a quantum information scientist at the University ...

Recommended for you

Scientists discover superconductor with bounce

October 23, 2017

The U.S. Department of Energy's Ames Laboratory has discovered extreme "bounce," or super-elastic shape-memory properties in a material that could be applied for use as an actuator in the harshest of conditions, such as outer ...

Scientists update four key fundamental constants

October 23, 2017

Paving the way for transforming the world's measurement system, an international task force has determined updated values for four fundamental constants of nature. The updated values comprise the last scientific piece of ...

Experiment provides deeper look into the nature of neutrinos

October 23, 2017

The first glimpse of data from the full array of a deeply chilled particle detector operating beneath a mountain in Italy sets the most precise limits yet on where scientists might find a theorized process to help explain ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.