Gravity measurements exert a particular fascination ranging from the everyday experience of feeling the gravitational force holding us on ground to the mysteries of general relativity and space time. Compared to other forces gravity is surprisingly weak, making shielding of gravitation practically impossible. Gravity measurements are ideally suited to look deep inside the ground and they have been used for over 100 years in fields as oil and mineral exploration, underground mapping and climate research. However, although gravity measurements are highly valued, there are some drawbacks in terms of long and tedious measurements and geological noise. GG-TOP responds to an increasingly pressing demand for a holistic development programme driving sensitivity of instrumentation, modelling instrument and geological noise, discriminating underground objects, fusing and presenting the information from multi-sensor systems. The GG-TOP consortium is truely multi-disciplinary uniting fundamental and applied physicists, civil and electrical engineers and archaeologists behind a joint goal. GG-TOP has a strong Stakeholder compontent with interactions at all levels and potential users directly influencing the research programme. GG-TOP will explicitly evaluate the potential of its new technology in applications as diverse as urban infrastructure (pipes, cables...) and void (cellars, tunnels,..) mapping, seabed inspection, archaeology and fundamental tests of physics. We anticipate the outcome of this programme to be a technology suite adaptable to various needs and leading to a range of follow-on product development programmes.

The Hub will create a seamless link between science and applications by building on our established knowledge exchange activities in quantum technologies. We will transform science into technology by developing new products, demonstrating their applications and advantages, and establishing a strong user base in diverse sectors. Our overarching ambition is to deliver a wide range of quantum sensors to underpin many new commercial applications. Our key objective is to ensure that the Hub's outputs will have been picked up by companies, or industry-led TSB projects, by the end of the funding period. The Hub will comprise: a strong fabrication component; quantum scientists with a demonstrated ability to combine scientific excellence with technological delivery; leading engineers with the broad collective expertise and connections required to develop and use new quantum sensors. We have identified, and actively involved, industry enablers to build a supply chain for quantum sensor technology. As well as direct physics connections to industry, the engineers provide strong links to relevant industrial users, thus providing information on industrial needs and enabling rapid prototype deployment in the field. To establish a coherent national collaborative effort, the Hub will include a UK network on quantum sensors and metrology, which will also exploit the connections that Prof Bongs and all Hub members have forged in Europe, the US and Asia. This inter-linkage ensures capture of the most advanced developments in quantum technology around the world for exploitation by the UK. Quantum sensors and metrology, plus some devices in quantum communication, are the only areas where laboratory prototypes have already proven superior to their best classical counterparts. This sets the stage, credibly, for rapid and disruptive applications emerging from the Hub. The selection of prototypes will be driven by commercial pull, i.e. each prototype project within the Hub must demonstrate, from the outset, industry or practitioner engagement from our engineering and/or industrial collaborators. We have strong industry support across several disciplines with the structures in place actively to manage technology and knowledge transfer to the industry sector. Particular roles are played by NPL and e2V. We will closely collaborate with NPL as metrology end-user on clock, magnetometer and potentially Watt balance developments with a lecturer-level Birmingham-NPL fellow contributed by Birmingham University and our PRDAs spending ~17 man-years in addition to 3-5 PhD students on these joint projects in the Advanced Metrology Laboratory/incubator space. E2v have a unique industrial manufacturing/R&D facility co-located within the School of Physics and Astronomy at Nottingham that has already catalysed the expansion of their activities into the Quantum Technology domain. Public Engagement conveying the Hub's breakthroughs will be a high priority - for example annually at the Royal Society Summer Exhibitions. In addition to cohort-training of 80 PhD students working within the Hub, the Hub will contribute to the training of ~500 PhD students via electronically-shared lectures (many already running within the e-learning graduate schools MPAGS, MEGS, SEPNET and SUPA) across the institutions within the Hub. The Hub will create an internationally-leading centre of excellence with major impact in the area of quantum sensors and metrology. To widen the impact of the Hub and ensure long-term sustainability, we will actively pursue European and other international collaborative funding for both underlying fundamental research and the technology development.