Toshiba Europe Ltd today announced 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
financial year 2035. 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 fiber 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 realization 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 fiber 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, 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 comments, "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."
The details of the advancement are published in the journal Nature
Photonics.
Technical Summary
QKD systems typically comprise a complex fiber-optic circuit, integrating
discrete components, such as lasers, electro-optic modulators,
beam-splitters and fiber couplers. As these components are relatively
bulky and expensive, the purpose of this work was to develop a QKD system in
which the fiber-optic circuit and devices are written in millimeter scale
semiconductor chips.
Toshiba has developed the first complete QKD prototype in which quantum
photonic chips of different functionality are deployed. Random bits for
preparing and measuring the qubits are produced in quantum random number
generator (QRNG) chips and converted in real-time into high-speed modulation
patterns for the chip-based QKD transmitter (QTx) and receiver (QRx) using
field-programmable gate arrays (FPGAs). Photons are detected using
fast-gated single photon detectors. Sifting, photon statistics evaluation,
time synchronization and phase stabilization are done via a 10 Gb/s optical
link between the FPGA cores, enabling autonomous operation over extended
periods of time. As part of the demonstration, the chip QKD system was
interfaced with a commercial encryptor, allowing secure data transfer with a
bit rate up to 100 Gb/s.
To promote integration into conventional communication infrastructures, the
QKD units are assembled in compact 1U rackmount cases. The QRx and QTx chips
are packaged into C-form-factor-pluggable-2 (CFP2) modules, a widespread
form-factor in coherent optical communications, to ensure forward
compatibility of the system with successive QKD chip generations, making it
easily upgradeable. Off-the-shelf 10 Gb/s small-form-factor pluggable (SFP)
modules are used for the public communication channels.
Taofiq Paraiso, lead author of the Nature Photonics paper describing the
chip-scale QKD system, says that "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."
Reference:
Taofiq Paraïso, A photonic integrated quantum secure communication system,
Nature Photonics (2021).
DOI: 10.1038/s41566-021-00873-0.