Quantum cryptography could finally hit the mainstream thanks to a deal that will allow customers to adopt the technology without having to install dedicated optical fibers.

Quantum cryptography--a means of keeping secrets safe by using light particles to help scramble data--has been commercially available for several years. But the technology has only been practical for governmental or large private-sector organizations that can afford to have their own point-to-point optical fiber that the technology requires. But under the new deal, struck between Siemens IT Solutions and Services in the Netherlands and Geneva, Switzerland-based id Quantique, any organizations or individuals wanting state-of-the-art data security will be able to buy the complete package of quantum cryptography and cable.

For the commercial development of quantum cryptography it's a significant step, says Seth Lloyd, an expert in the subject and a professor at MIT. "It makes it a lot more commercially viable. The fiber is by far the most expensive part," he says.

Quantum cryptography is a method that seeks to solve the problem of how to securely send cryptographic keys between two parties by encoding them within light particles, or photons. It allows the parties to share a random--and so almost unbreakable--key without fear of third-party interception. If anyone does try to eavesdrop on the key exchange, the mere act of observing the photons changes them, making the attack detectable.

But for this quantum key distribution (QKD) to work, the same photons transmitted by one party have to be received by the other. This means that unlike most optical fiber data signals, which are periodically amplified by repeaters to boost the signal, quantum keys can only be sent through dedicated, unamplified, point-to-point fibers.

Telecom companies have spent the last few years installing precisely this kind of fiber, but for entirely different reasons, says Lloyd. Known as dark fiber, this is essentially extra capacity that has been laid in bulk to accommodate future growth.

Some companies lease this dark fiber for their own secure data connections, but for the most part it's just laying there waiting for deployment, says Andrew Shields, head of Toshiba Research Europe's Quantum Information Group in Cambridge, U.K. "For quantum key distribution, this is a godsend. There is all this dark fiber in the ground right now that's not being used."

In the new deal, Siemens SIS will offer id Quantique's QKD system over Siemens' existing dark fiber. "It's important from a commercial point of view that companies like Siemens, a global player, are showing an interest in this technology," says Grégoire Ribordy, co-founder and CEO of id Quantique. "There's potential to really accelerate commercial development."