Quantum cryptography has emerged from the laboratory and into the real world.
Single photons carry the quantum codes
Using properties of quantum physics, the technique encrypts data with keys that reveal if they have been intercepted or tampered with.
US company Magiq and Swiss firm ID Quantique have already sold hardware to several customers keen to protect data with quantum cryptography.
Governments and armed forces are thought to be among the first users of the technology.
Encryption usually involves scrambling data with long numeric keys that stop other people reading it.
The information inside the message is effectively kept secure because of the time it would take an eavesdropper to sort through all possible keys used to scramble the data.
But quantum cryptography scrambles data in a different way by using the strange properties of the quantum world to guarantee that keys have been swapped securely.
Information about the key is encoded on to a single photon of light.
Quantum physics guarantees that the properties of the photon will change if anyone intercepts it and tries to read the information off it.
Once two parties have swapped a key that they know to be safe they can be sure that the messages they are sending each other are secure.
"Once you can guarantee the key is secret, you can use that for encrypting the data or for any other cryptographic tasks you want to do," said Dr Andrew Shields, leader of the Quantum Information Group at Toshiba's Cambridge laboratory.
Bob Gelfond, chief executive at Magiq, said the improvements in security offered by quantum cryptography were proving popular even though its QPN Security Gateway cost between $50,000 and $100,000.
Keeping data secure is getting harder
Once connected to a fibre-optic network the Magiq hardware allows companies to set up a virtual network they can use to send data encoded with quantum keys.
Mr Gelfond said quantum cryptography had been established in laboratories for years but Magiq's engineers had worked hard to turn it into a commercial device.
"I think a lot of people thought it would happen later rather than sooner because of those engineering challenges," he said. "That was our challenge; making the system robust enough so it would work in a typical technology environment."
Although the technology is already in use, there are still some limitations to iron out.
For instance there is a limit to the distance that photons can travel before they lose coherence which makes it impossible to read key information.
The current record for long-distance quantum key distribution is 120km.
Mr Gelfond said now the basic technology was established costs of components and optics would fall.
Magiq was also getting a lot of interest from net service firms, said Mr Gelfond, who wanted to use quantum cryptography to create ultra-secure lines they could sell for a premium.
Mr Gelfond said his company was working on quantum memory chips, single photon sources and quantum repeaters to help with its long-term goal of creating a commercial quantum computer.