Is quantum sensing the closest quantum technology to application?
Wrachtrup — I'd say that quantum sensor technology is one life cycle ahead of quantum computing. There are already start-ups and small companies that offer quantum sensors. Of course, this is not yet a mass market. Simple quantum sensors are already in use; for more complex problems, it will become clear in the next few years whether they will be just as successful and whether it will be possible to replace and improve marketable magnetometers such as those currently installed in cell phones and computers.
Vidal — At Fraunhofer IAF, we are currently working on implementing quantum sensing to detect magnetic fields and microwave sources applied to fields as diverse as nano- and micro-electronics, chemistry, medicine, material science, and navigation. Other applications for diamond-based sensors that are close to the market include detection of magnetic fields, gravimetry, and inertial navigation. Who knows, we might need them in our cell phones when we head off to explore space some time.