Much has been heard recently about quantum computing and its qubits, but this field of physics and engineering that exploits properties of subatomic particles also has application in the sensor segment. And, ironically, this is an area with the most potential for practical use in photovoltaic cells, semiconductors, medical imaging equipment and defence, according to a recent article by the Boston Consulting Group (BCG). BCG predicts the emergence of new uses for quantum sensor technology over the next decade, with very transformative effects. Some 1,600 patents have already been granted, and startups have raised $2bn by 2022. These figures are some of the indications that the total addressable market for these types of sensors will be in the range of $3bn to $5bn by 2030, which represents either a 2% to 3% share of the wider sensor market. Research by IDTechEx, covering a horizon up to 2044, estimates that applications of quantum sensors in electric vehicles, GPS-free navigation systems, medical imaging and quantum computing are expected to reach $7.1bn. The extreme sensitivity of quantum sensors provides high accuracy in various types of measurement, such as time, frequency, acceleration, temperature, pressure, among others. Several scenarios can benefit from this accuracy, including consumer products in the medium and long term, in the view of BCG, which divides quantum sensors into five main application classes: 1. Electromagnetic Sensors: Used to measure electromagnetic fields dynamically and with high accuracy, e.g. to intercept communications in the defense field or to record brain activity in the diagnostic field. 2. Image Production: By improving the resolution and range of images, quantum technology can create more accurate 3D maps and make more precise measurements. Quantum radars can help detect and localize objects. 3. Gravimeters and Gradiometers: These are pieces of equipment that measure the strength and changes in a gravitational field used to monitor geophysical phenomena. 4. Thermometers and Barometers: They can more accurately assess temperature and atmospheric pressure and thus improve the measurement of environmental parameters in aircraft, for example. 5. Cross-cutting Applications. Combined use with quantum computing and communication for weather forecasting, fraud detection, traffic optimization, among other applications. BCG warns that the biggest challenges to adoption of quantum sensors are upfront and operational costs and the current lack of clarity about the advantages this emerging technology can deliver. Not to mention integration difficulties, limited scalability and a lack of standardisation for now. BCG adds that each stage of the quantum sensor value chain, consisting of components, sensors themselves, applications, and services, is maturing at different rates, making it difficult to predict how this market will evolve in the coming years. The strategic nature of the defense industry and its lower price sensitivity compared to other industries is making the military the main driver of the quantum sensor market. Three other sectors expected to benefit soon from quantum sensors are healthcare, electronics manufacturers, geology & energy. 'Google Maps' of the underground Delta g, a new company resulting from a spin-out from the University of Birmingham, recently raised £1.5m in investment to accelerate the commercial availability of quantum sensors to map the underground. The company uses a technology developed at the university as part of a quantum sensor technology hub that aims to transform the efficiency of large infrastructure and repair projects by mapping complex, low-visibility sites quickly, accurately and without the need for excavation. Infrastructure projects, such as roadworks, need to rely on accurate surface-level information to enable visualisation of underground locations. However, today's mapping tools are limited due to poor ability to see beyond the upper layers and to making inconsistent measurements in different ground conditions and in high vibration environments, resulting in prohibitive time and financial costs. Delta g's work will build on research into gravitational gradiometry carried out over the past decade in Birmingham that culminated in the world's first field demonstration of a practical quantum sensor for detecting underground infrastructure, the researchers said. Delta g is focussing its efforts on a new approach to mapping complex subsurfaces. According to the company, this will lead to the creation of 'Google Maps for the subsurface' in a fast and accurate way that is cost-effective and scalable. Its potential benefits will be applicable to sectors such as construction and utilities. "It is exciting to see this investment in quantum sensors, which will be used to pursue new tools that aim to bring benefits to applications across civil engineering," says Michael Holynski, Professor of Quantum Sensing at the University of Birmingham and founder of Delta g.