LONDON Researchers at the Cambridge Research Lab of Toshiba Research Europe Ltd have increased the bit rate of quantum key distribution (QKD) more than hundred-fold. They suggest the breakthrough will allow secure QKD to be used on optical networks with multiple nodes.
Until now, the low secure key distribution speeds, typically as low as 10kbits/s over a 20km distance, restricted the technology to point-to-point links.
The work was the result of engineers finding a way to make hardware more able to filter the electron avalanches that normally limit the technology than has previously been possible.
Using this method Toshiba has increased the clock rate of their QKD system to 1.036 GHz, approaching the value used in conventional optical communications.
As the detector is based on a compact and robust semiconductor device, it is said to be suitable for real-world applications. Toshiba now plans to develop a fully functional prototype of the high bit rate QKD system.
Dr Andrew Shields, leader of the Quantum Information Group at the Cambridge Research Labs, said: "I am quite sure this will become the standard for information security. The information is perfectly safe and virtually hack and tap proof."
The CRL team has basically developed a way to harness usable signals from much weaker electron fields without propagating noise, allowing clock speeds to be ramped up to over 1GHz. According to Shields, this allows a raw bit rate of 9Mbits/s over a 20km fibre link, or 1MBits/s in fully secure mode.
The new system also displays record bit rates for longer optical fibre lengths. For a 100 km fibre the secure bit rate is 10.1 kbit/s. This is over an order of magnitude higher than previously reported values.
The reason that Toshiba's new system is so much faster is that it has created a photon detector which is 100 times faster than the old system.
In a parallel development, the Toshiba team has also designed and successfully implemented hardware (based on their older kb/s technology) in the first QKD network launched Wednesday (Oct.8) in Vienna, Austria.
This network is the result of a collaboration of 41 QKD R&D teams across Europe funded by the EC through the Integrated Project SECOQC.
"Together, the dramatic increase in bit rate and the possibility of network deployment, herald a breakthrough in the applicability of QKD technology. We plan now to develop a fully functional prototype of the high bit rate QKD system for use in quantum networks," said Shields.