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Magnetic resonance imaging is an indispensable medical tool, and produces images of matter by scanning the magnetic fields of a sample's atomic nuclei or electrons. Imaging at the single-molecule level is an unachieved goal that could have new applications such as quantum computing. On page 644, Mikhail Lukin at Harvard University and his colleagues report creating a novel quantum magnetic sensor able to achieve nanometre-scale resolution by manipulating the spin of an individual electron in an impurity in diamond. In a companion paper on page 648, a group led by Jorg Wrachtrup of the University of Stuttgart in Germany uses a similar approach to create an image scanning system. Lukin tells Nature that, together, these papers may make a new quantum-imaging device a reality.

How is your 'nanosensor' innovative?

In the past, scientists couldn't get a magnetic sensor in close enough proximity to a magnetic source at such small scale. The fundamental sources of magnetic resonance in molecules are the atomic nuclei, which produce extremely weak magnetic fields and so require a sensor that is small but sensitive. During the past few years we've studied how single spins evolve in diamond and realized two things: first, that single spins act as sensitive probes of their magnetic environment and so can be used as tiny detectors and, second, that we can control these spins very well. By applying quantum-control techniques to a single spin in a diamond nanocrystal, we achieved a sensor with high sensitivity and nanoscale resolution.

How do the papers complement each other?

Combined, these two techniques are a big step towards a long-standing goal of creating quantum devices. We made a nanosensor by controlling individual spins in diamond. Jorg's group showed how a scanning system could use diamond nanocrystals, which contain single spins, for imaging. Together, the techniques may result in a nanometre-scale magnetic-imaging approach.

Will this work have a major impact?

Our sensor should allow the reading, writing and possibly transportation of quantum bits of information encoded in electron or nuclear spin 'memory', which are necessary for quantum computing. And because the sensor works at room temperature, it could be used in living cells or to monitor the structure and dynamics of complex molecules.

Will this work transform your career?

I don't know. I'm extremely intrigued by its range of possibilities, but at the same time the work is only a stepping stone towards practical sensors.