Toshiba shrinks gigahertz rate QKD technology to chip scale

27 Oct 2021

Company describes solution as “an entirely standalone secure communication system based on photonic integrated circuits.”

Toshiba Europe has announced it has developed the world’s first chip-based quantum key distribution (QKD) system. This advance, says the company, will enable the mass manufacture of quantum security technology, bringing its application to a much wider range of scenarios including to Internet of Things (IoT) solutions.

QKD addresses the demand for cryptography which will remain secure from malicious attack. In particular, a large-scale quantum computer will be able to efficiently solve the difficult mathematical problems that are the basis of the public key cryptography widely used today for secure communications and e-commerce.

In contrast, the protocols used for quantum cryptography can be proven secure from first principles and will not be vulnerable to attack by a quantum computer, or indeed any computer in the future. The QKD market is expected to grow to approximately $20 billion worldwide in FY2035 – according to Toshiba’s long-term estimate based on estimates by research firms.

Large quantum-secured fiber networks are currently under construction in Europe and South-East Asia, and there are plans to launch satellites that can extend the networks to a global scale.

In October 2020, Toshiba released two products for fiber-based QKD, which are based on discrete optical components. Together with project partners, Toshiba has implemented quantum-secured metro networks and long-distance fibre optic backbone links in the UK, Europe, US and Japan.

Manufacturing advances

For quantum cryptography to become as ubiquitous as the algorithmic cryptography we use today, it is important that the size, weight and power consumption are further reduced. This is especially true for extending QKD and quantum random number generators (QRNG) into new domains such as the last-mile connection to the customer or IoT. The development of chip-based solutions is essential to enabling mass market applications, which will be integral to the realisation of a quantum-ready economy.

Toshiba says it has developed techniques for shrinking the optical circuits used for QKD and QRNG into tiny semiconductor chips. These are not only much smaller and lighter than their fibre optic counterparts, but also consume less power.

Most significantly, many can be fabricated in parallel on the same semiconductor wafer using standard techniques used within the semiconductor industry, allowing them to be manufactured in much larger numbers. For example, the quantum transmitter chips developed by Toshiba measure just 2x6mm, allowing several hundred chips to be produced simultaneously on a wafer.

Andrew Shields, Head of Quantum Technology at Toshiba Europe, commented, “Photonic integration will allow us to manufacture quantum security devices in volume in a highly repeatable fashion. It will enable the production of quantum products in a smaller form factor, and subsequently allow the roll out of QKD into a larger fraction of the telecom and datacom network.”

Taro Shimada, Corporate Senior Vice President and Chief Digital Officer of Toshiba Corporation said, “Toshiba has invested in quantum technology R&D in the UK for over two decades. This latest advancement is highly significant, as it will allow us to manufacture and deliver QKD in much larger quantities.

“It is an important milestone towards our vision of building a platform for quantum-safe communications based upon ubiquitous quantum security devices,” he said.

Part of this work was funded by the Innovate UK Collaborative R&D Project AQuaSeC, through the Industrial Strategy Challenge Fund. The details of the advancement are published in Nature Photonics.

Taofiq Paraiso, lead author, commented, “We are witnessing with photonic integrated circuits a similar revolution to that which occurred with electronic circuits. PICs are continuously serving more and more diverse applications.

“Of course, the requirements for quantum PICs are more stringent than for conventional applications, but this work shows that a fully deployable chip-based QKD system is now attainable, marking the end of an important challenge for quantum technologies. This opens a wide-range of perspectives for the deployment of compact, plug-and-play quantum devices that will certainly strongly impact our society.”