Why Toshiba QKD

Pioneering technology and unparalleled expertise developed over nearly two decades of research

We started research into quantum cryptography in 2003 at the Cambridge Research Laboratory of Toshiba Research Europe Limited. Since then we have demonstrated a number of notable world firsts. We were the first to announce quantum key distribution over 100 km of fiber in 2004 and the first with a continuous key rate exceeding 1 Mbit/second in 2010 and 10 Mbit/second in 2017.

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This impressive heritage and experience has enabled us to create a range of cutting edge technologies and products that differentiate Toshiba as the leading provider of QKD technology. Toshiba has pioneered several technologies which contribute to its high performance QKD solution:

High Key Rates

We have achieved the highest continuous secure key rate for a QKD system to date of 13.7 Mb/s over a fiber distance of 10 km. Toshiba realized the improved quantum key distribution speed, the world’s fastest, by developing high speed detectors and electronics for registering the photon signals, as well as new faster methods for post-processing of the signals into a secret key. The new methods include realization of the error correction and privacy amplification steps in hardware, which greatly improves the post-processing speed and overcomes the bottleneck in current software implementations.

Long Range

We have demonstrated practical QKD over fiber links up to 240km in length. This was achieved using semiconductor avalanche photodiodes which can be thermoelectrically cooled without using cryogens.

Furthermore, we invented and demonstrated a new protocol called Twin-Field QKD that allows the range of a link to be extended to over 500km of fiber. This enables the protection of sensitive data transmitted in optical networks between cities, allowing for the creation of a secure link between cities like London, Paris, Brussels, Amsterdam and Dublin.

In Twin-Field QKD, light pulses are sent from both ends of the fiber to a central location, where a photon is detected. Provided it is impossible to tell which end of the fiber the photon came from, this technique effectively doubles the transmission distance at a given rate. Although conventional systems may be daisy-chained together to increase the total transmission distance, this requires that the intermediate stations are in a secure location. In contrast, no physical protection in the central location is necessary for the security of Twin-Field QKD. This would enable a bank in London, for instance, to move highly sensitive customer data to a data center in Leeds within the current conventional fiber-optic network without the fear of the data being compromised.

Data Co-existence

Deployment of QKD has been hampered by the frequent need for dedicated dark fibers to segregate the very weak quantum signals from conventional traffic. Up until now the coexistence of QKD with data has been limited to bandwidths that are orders of magnitude below those commonly employed in fiber optic communication networks. Using an optimized wavelength divisional multiplexing scheme, we transport QKD and the prevalent 100 Gb/s data format in the forward direction over the same fiber. We show a full quantum encryption system operating with a bandwidth of 200 Gb/s over a 100 km fiber. These results suggest it will be possible to integrate QKD and other quantum photonic technologies into high bandwidth data communication infrastructures, thereby allowing their widespread deployment.

Networking Technologies

Our key management software allows key distribution within a network environment and over arbitrary distances, utilising REST-based interface standardised by ETSI Industry Specification Group in QKD.

Active Stabilisation

We have pioneered active stabilisation technology that allows the system to distribute key material continuously, in even the most challenging operating conditions, without any user intervention. This avoids the need for recalibration of the system due to temperature-induced changes in the fiber lengths.

Initiation of the system is also managed automatically, allowing simple turn-key operation. It has been shown to work successfully in several network field trials. The system can be used for a wide range of cryptographic applications, e.g., encryption or authentication of sensitive documents, messages or transactions. A programming interface gives the user access to the key material.

The system is also easy to manage, with initiation handled automatically and an intuitive programming interface providing the user with access to key materials. The technology includes pioneering active stabilisation technology which allows the system to distribute key material continuously, in even the most challenging operating conditions, without any user intervention. This avoids the need for recalibration of the system due to temperature-induced changes in the fiber lengths.

The reliability and stability of the Toshiba QKD system has been demonstrated in numerous deployments. For example, the Cambridge Quantum Network ran for 18 months with the only down time due to power failures and operational down time to introduce new software

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Ultimate security

The Toshiba QKD system uses an efficient implementation of the BB84 protocol, which has been rigorously proven to be secure from all types of attack, even those using a quantum computer. It deploys secure, quantum-safe authentication of the data used to form the quantum keys.

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