Photonic Quantum-Enhanced Sensors

Sensors permeate our society, measurement underpins quantitative action and standardized accurate measurements are a foundation of all commerce. The ability to measure parameters and sense phenomena with increasing precision has always led to dramatic advances in science and in technology - for example X-ray imaging, magnetic resonance imaging (MRI), interferometry and the scanning-tunneling microscope. Our rapidly growing understanding of how to engineer and control quantum systems vastly expands the limits of measurement and of sensing, opening up opportunities in radically alternative methods to the current state of the art in sensing. Through the developments proposed in this Fellowship, I aim to deliver sensors enhanced by the harnessing of unique quantum mechanical phenomena and principles inspired by insights into quantum physics to develop a series of prototypes with end-users. I plan to provide alternative approaches to the state of the art, to potentially reduce overall cost and dramatically increase capability, to reach new limits of precision measurement and to develop this technology for commercialization.

Light is an excellent probe for sensing and measurement. Unique wavelength dependent absorption, and reemission of photons by atoms enable the properties of matter to be measured and the identification of constituent components. Interferometers provide ultra-sensitive measurement of optical path length changes on the nanometer-scale, translating to physical changes in distance, material expansion or sample density for example. However, for any canonical optical sensor, quantum mechanics predicts a fundamental limit of how much noise in such experiment can be suppressed - this is the so-called shot noise and is routinely observed as a noise floor when using a laser, the canonical "clean" source of radiation.

By harnessing the quantum properties of light, it is possible reach precision beyond shot noise, enabling a new paradigm of precision sensors to be realized. Such quantum-enhanced sensors can use less light in the optical probe to gain the same level of precision in a conventional optical sensor. This enables, for example: the reduction of detrimental absorption in biological samples that can alter sample properties or damage it; the resolution of weak signals in trace gas detection; reduction of photon pressure in interferometry that can alter the measurement outcome; increase in precision when a limit of optical laser input is reached. Quantum-enhanced techniques are being used by the Laser Interferometer Gravitational Wave Observatory (LIGO) scientific collaboration to reach sub-shot noise precision interferometry of gravitational wave detection in kilometer-scale Michelson interferometers (GEO600). However, there is otherwise a distinct lack of practical devices that prove the potential of quantum-enhanced sensing as a disruptive technology for healthcare, precision manufacture, national security and commerce.

For quantum-enhanced sensors to become small-scale, portable and therefore practical for an increased range of applications outside of the specialized quantum optics laboratory, it is clear that there is an urgent need to engineer an integrated optics platform, tailored to the needs of quantum-enhanced sensing. Requirements include robustness, miniaturization inherent phase stability and greater efficiency. Lithographic fabrication of much of the platform offers repeatable and affordable manufacture. My Fellowship proposal aims to bring together revolutionary quantum-enhanced sensing capabilities and photonic chip scale architectures. This will enable capabilities beyond the limits of classical physics for: absorbance spectroscopy, lab-on-chip interferometry and process tomography (revealing an unknown quantum process with fewer measurements and fewer probe photons).

Historically, advances in precision sensing and measurement have had significant societal impact through commerce, national security, advances in healthcare and precision interferometry for manufacture.

This ambitious Fellowship offers a new paradigm in disruptive sensing and measurement technologies. The fundamental limits of measurement will be expanded, and alternative approaches to canonical sensors will be realized to greatly enhance capability, to reduce overall cost and simplify operation. This Fellowship is designed to have impact further than academic research, both during the Fellowship lifetime and beyond; such as:

- Training skilled technical and research personnel in the engineering and application of practical quantum technology will have far reaching benefits for the UK knowledge economy for the next 30 years. This will occur through the direct training of the PDRAs and PhD studentships working on this project, the researchers of my collaborators and project partners. The results of this Fellowship will motivate future generations of science and engineering researchers.

- Societal impact through increased security: The "Blue lights" services will likely find use of increased sensing precision of deployable, practical systems - I will work with partner DSTL (the Defense Science and Technology Laboratory) to optimse impact in this area by exploring application of sub shot noise spectroscopy for trace chemical detection. DSTL's stated purpose is "to maximise the impact of science and technology for the defence and security of the UK."
(https://www.gov.uk/government/organisations/defence-science-and-technology-laboratory/about)

- The UK economy, high tech business and industry: Increased precision of measurement and sensing impacts on increasingly precise methods for micro- and nano-fabrication and for future drug discovery in the pharmaceuticals industry. For instance, the current limitations experienced by the pharmaceuticals industry include degradation of samples by regular measurement and the obscuring of weak signals due to shot noise. Greater precision and the ability to recover and reuse high value assays will be important factors in the sustained output and competitiveness of the industry - I will work with partner AstraZeneca to engineer quantum-enhanced sensing systems to be compatible with high-throughput screening for future drug discovery. This example in turn impacts on society through improving healthcare. My direct engagement with industry will enable me to educate their personnel on quantum technology. Project progress will disseminate through the networks of each partner and their own supply chains - e.g. partner the National Physics Laboratory (NPL) has considerable experience of "ensur[ing] cutting edge measurement science and technology ha[s] a positive impact in the real world [... to] deliver world-leading measurement solutions that are critical to commercial research and development, and support business success across the UK and the globe" (http://www.npl.co.uk/about/what-is-npl/). I will have access to NPL's expertise in achieving this.