Seeing with radio waves — ScienceDaily

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Scientists from the University of Tsukuba’s Division of Physics have used the quantum effect called “spin-locking” to dramatically improve resolution when imaging nitrogen starvation flaws in diamond by radiofrequency. This work could lead to faster and more accurate materials analysis, as well as a path to practical quantum computers.

Nitrogen vacancy (NV) centers have long been studied for their potential use in quantum computers. An NV center is a type of defect in the lattice of a diamond, in which two adjacent carbon atoms have been replaced by a nitrogen atom and a void. This leaves an unpaired electron, which can be detected using radio frequency waves, since its probability of emitting a photon depends on its spin state. However, the spatial resolution of radio wave detection using conventional radio frequency techniques has remained less than optimal.

Now, researchers at the University of Tsukuba have pushed the resolution to its limit by employing a technique called “spin-locking”. The microwave pulses are used to put the spin of the electron into a top-down quantum superposition simultaneously. Then, a driving electromagnetic field causes the direction of the spin to precess, like a wobbling top. The end result is an electronic spin shielded from random noise but strongly coupled to the detection equipment. “Twist-locking ensures high accuracy and sensitivity of electromagnetic field imaging,” says first author Professor Shintaro Nomura. Due to the high density of NV centers in the diamond samples used, the collective signal they produced could be easily picked up with this method. This allowed the detection of collections of NV centers at the micrometer scale. “The spatial resolution we achieved with RF imaging was much better than with existing similar methods,” Prof. Nomura continues, “and it was only limited by the resolution of the light microscope we used.”

The approach demonstrated in this project can be applied in a wide variety of application areas – for example, characterizations of polar molecules, polymers and proteins, as well as the characterization of materials. It could also be used in medical applications – for example, as a new way to perform magnetocardiography.

This work was supported in part by a Scientific Research Assistance Grant (nos. JP18H04283, 291 JP18H01243, JP18K18726, and JP21H01009) from the Japan Society for the Promotion of 292 Science.

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Material provided by University of Tsukuba. Note: Content may be edited for style and length.

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