Quantum-enhanced THz spectroscopy and imaging

Quantum mechanics promises to be the driving force underneath the next technological revolution, and quantum cryptography, providing a commercial solution for the ultimate security, may well be considered the harbinger of this change. With this proposal, we aim at showing how quantum mechanics can allow to overcome the limits faced in the detection of long wavelength radiation, specifically at terahertz frequencies.

Terahertz is a portion of the electromagnetic spectrum that is both extremely hard to access to, and incredibly important from a technological standpoint. It is indeed a key player in security (explosives, drugs, and hazard-free concealed weapons detection), telecommunications (increased data-rate of short distance wireless communication), monitoring and quality control (spectroscopy). Despite its high potential, the lack of efficient sources and detectors prevents a widespread commercial application of terahertz time-domain spectroscopy and imaging.

Yet, a number of high-tech companies are investing into terahertz technology and recent market studies hint for a 40%/year increase in the turnover associated to this technology.

It is therefore vital to identify now strategies for overcoming the limitations of the current terahertz detectors. This proposal aims at developing such a strategy exploiting the unique properties of quantum, entangled states of light.

Entangled photons, separated in space but sharing a common wavefunction, can be generated by commercial nonlinear crystals and boost unusual properties not accessible by classical means. Two of these properties, namely the ability to acquire twice the phase of a classical state upon propagation and the reduced amplitude noise below the classical shot-noise limit, offer a mean for increasing the sensitivity of terahertz time-domain detectors, that operate indeed as a differential phase sensor. Combining such an improvement with recent concepts of super-resolved imaging will also result in an increased resolution of long wavelength mapping.

Combining for the first time concepts of quantum optics, recognised as a main pillar for our future technology, and of terahertz photonics, boosting a number of underdeveloped application potential, this proposal is in line with the research strategy set by the UK research councils, and promise to deliver impact on a number of different disciplines, such as biology and material science, as well as on the quality control and security inspection activities.

This proposal aims at developing an application of quantum optics targeting an increase in our detection capability in the terahertz portion of the electromagnetic spectrum.

The majority of the research on quantum optics so far addressed fundamental questions, however the amount of knowledge accumulated has now reached the critical mass able to deliver high-impact technologies. This is the main drive underneath the multi-million pounds' investments in quantum-related researches by Canada, US, EU, Japan and for the 270 million pounds the UK Government has devoted to quantum technologies research via the UK National Quantum Technologies Programme. On the other hand, the terahertz spectral region is extremely important from a technological standpoint as it offers advantages compared with competing technologies in fields such as biological and medical imaging, security inspection, quality control and telecommunications. Several UK companies such as Teraview, QMC-instruments and ThruVision Systems, as well as other international players (Menlo Systems, Toptica, Rainbow Photonics, TeTechs, Gentec) are developing technologies and investing to secure their share in what is expected to be a billion pounds' market, by 2024 (BCC news source). Therefore, the success of this project will both contribute to develop a strategic scientific objective and to a growing commercial opportunity.

- Academy. From an academic perspective, the impact will be delivered thanks to a direct engagement with the staff from the Glasgow-led Quantum Hub (QuantIC), and via an intense and and effective dissemination strategy encompassing participation to international conferences, publication of journal papers and collaborations with world renown leaders in the area of research tackled by the proposal, as described in the Academic beneficiaries section.

- Economy. The commercial potential will be tested thanks the active participation to the research efforts of an international industrial partner (TeTechS, CA), the support and the precious feedbacks from a UK leading terahertz company (QMC-instruments), the possibility to access the QuantIC 4M£ Partnership Resource Fund and to obtain the expert feedback on technology transfer matters from the QuantIC Business Development Manager, part of the Hub support package.

- Society. To improve the social impact of this project we plan to perform outreach and public engagement activities with the aim of educating the public on basic concepts of quantum mechanics and the role they will play in the forthcoming technology. Also in this case an effective strategy will be devised with the support of the QuantIC Hub, via the help of its Public Engagement and Communication Officer. In addition, to maximise the effectiveness of the communication, we shall rely on the professional work of graphic designers for the preparation of dissemination material.