Optical metrology for quantum enhanced secure telecommunication

Organisations such as the banking, defence and security, and medical records sectors, face continual and escalating operational challenges in their efforts to protect vital data communications infrastructures. Additional risks could also arise in future should practical quantum computing be realised, as the predicted breakthrough problem-solving capabilities of such systems might quickly crack the types of encryption that form the mainstay of modern security protections.

Fortunately, quantum physics points to a solution, in the form of Quantum Key Distribution (QKD). This communication technology offers the potential to reveal the uninvited attention of any eavesdropper, revealed by an inevitable change of ‘quantum state’ of the communications signals that would be used to carry sensitive data.

QKD, therefore, offers disruptive market potential for assuring communications data security, and huge competitive advantage to European businesses that adopt it. So far, however, confidence in the security of QKD systems can only be offered in theory, as security researchers have uncovered or envisioned vulnerabilities in component technologies, be it unforeseen or undocumented, that may be exploitable as ‘backdoors’ of utility to hackers.

Countermeasures were developed in the previous MIQC project, but confidence in QKD device security cannot be assured without rigorous methods to characterise, and therefore understand, behaviours of device components. Confidence was also limited by a lack of suitable measurement services to test protection measures and by an absence of published security evaluation standards.

The project devised methods and procedures to test critical components of QKD systems, including single-photon sources and detectors, and telecommunications hardware such as modulators and filters. This research built on the EMRP projects: Single-photon sources for quantum technologies and Metrology for Industrial Quantum Communication Technologies. Efficient, cost-effective measurement techniques for developing countermeasures to hacking attacks were developed for existing QKD systems, plus foundational metrology for next-generation entanglement-based QKD systems was devised. Permanent facilities for calibrating single photodetectors were also established, and pilot measurement comparison studies performed for single-photon detectors, attenuated laser and heralded single-photon sources. This resulted in a pilot calibration service for QKD devices, provided by METAS. Also, best practice guides were published on how to characterise countermeasures to hacking attempts, and on characterising components of free-space QKD systems.

During and after the conclusion of the project, the consortium supported the development of QKD-related specifications within the European Telecommunications Standards Institute (ETSI), resulting in two new specifications, plus a further two scheduled for publication in 2020.

The project demonstrably improved the robustness of commercial QKD system components. For example, participation in the project enabled Micro Photon Devices to develop enhancements to its PDM-IR single-photon counter, while the pilot calibration service helped ID Quantique identify potential security vulnerabilities, and guided modifications, for its d220 single-photon detector. Toshiba Research Europe Limited (TREL) provided substantial support to ETSI specification development, that helped it to develop prototype ultra-compact QKD devices.

In combination, confidence in the potential for the secure operation of QKD devices in adversarial environments has been significantly advanced, a process now being advanced by the European Metrology Network for Quantum Technologies.