Toshiba Shrinks Quantum Key Distribution Technology to a Semiconductor Chip

Overview of a chip-based quantum cryptography communication system

Toshiba Europe announced last week it has developed the world’s first chip-based quantum key distribution (QKD) system. This advance 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 attack by the supercomputers of tomorrow. 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*. Large quantum-secured fibre 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 fibre-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. 

A QKD chip under test at Toshiba’s Cambridge Research Laboratory Figure 2: Prototype optical integrated circuit and chip-based quantum cryptography communication system. (Top row, from left: quantum transmitter chip, quantum receiver chip, quantum random number generator chip. Bottom row: Chip-based quantum cryptography communication system)

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 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. 

A Toshiba scientist examines a QKD chip under the microscope at the company’s Cambridge Research Laboratory

Andrew Shields, Head of Quantum Technology at Toshiba Europe, remarked, “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 commented, “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.” 

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