Quantum technology is going green.
A new version of highly sensitive magnetic field sensors ditches the power-hungry lasers that previous devices relied on to make their measurements and replaces them with sunlight. Lasers can draw about 100 watts of power, like keeping a bright lightbulb on. The innovation potentially frees quantum sensors from that energy need. The result is a ecological prototype at the forefront of technology, the researchers report in an upcoming issue of Physical Review X Energy.
The big twist is on What the device uses sunlight. It does not use solar cells to convert light into electricity. Instead, sunlight does the work of laser light, says Jiangfeng Du, a physicist at the University of Science and Technology of China in Hefei.
Quantum magnetometers typically include a powerful green laser to measure magnetic fields. The laser shines in a diamond containing atomic defects (Serial number: 02/26/08). The flaws result when nitrogen atoms replace some of the carbon atoms that pure diamonds are made of. The green laser causes nitrogen defects to fluoresce, emitting red light with an intensity that depends on the strength of the surrounding magnetic fields.
The new quantum sensor also needs green light. There’s a lot of that in sunlight, as seen in the green wavelengths reflected off the leaves of trees and grass. To collect enough to power their magnetometer, Du and his colleagues replaced the laser with a 15-centimeter-wide lens to capture sunlight. They then filtered the light to remove all colors except green and focused it on a diamond with defects in the nitrogen atoms. The result is a red fluorescence that reveals the strength of magnetic fields just as laser-equipped magnetometers do.
Changing energy from one type to another, as it happens when solar cells collect light and produce electricityis an inherently inefficient process (Serial number: 7/26/17). The researchers say that avoiding the conversion of sunlight into electricity to power the lasers makes their approach three times more efficient than would be possible with the solar cells that power the lasers.
“I have never seen any other report connecting solar research with quantum technologies,” says Yen-Hung Lin, a physicist at the University of Oxford who was not involved in the study. “It could well ignite a spark of interest in this unexplored direction, and we could see more interdisciplinary research in the field of energy.”
Quantum devices sensitive to other things, like electric fields or pressure, could also benefit from the sunlight-driven approach, the researchers say. In particular, space-based quantum technology could use the intense sunlight available outside of Earth’s atmosphere to provide tailored light for quantum sensors. The remaining light, at wavelengths not used by quantum sensors, could be relegated to solar cells that power electronics to process quantum signals.
The solar-powered magnetometer is just a first step in merging quantum and environmentally sustainable technology. “In the current state, this device is mainly for development purposes,” says Du. “We hope that the devices will be used for practical purposes. But there is [is] a lot of work to do.”