Toshiba team extends quantum link range past 600km

Dual-band optical stabilization technique cancels out temperature effects that have limited the utility of quantum key distribution.

Researchers at Toshiba’s facility in Cambridge, UK, have dramatically extended the range of quantum-encrypted communication over optical fiber.

Andrew Shields and colleagues, who have just published their work in the journal Nature Photonics, report that a new optical technique called “dual-band stabilization” is able to cancel out temperature fluctuations in fiber that have the effect of scrambling quantum bits (qubits) of information over long distances.

Until now, that has limited commercial quantum key distribution (QKD) to less than 200 km. But when used in combination with Toshiba’s twin-field QKD approach, a range of 600 km has now been demonstrated.

“This latest advance extends the maximum span of a quantum link, so that it is possible to connect cities across countries and continents, without using trusted intermediate nodes,” noted Shields, head of the Toshiba Quantum Information Quantum Technology Division at Toshiba Europe.

“Implemented along with satellite QKD, it will allow us to build a global network for quantum secured communications.”