Diamond based device could be quantum network building block
1 min read
A proof of concept device created by US researchers could pave the way for on chip optical quantum networks.
According to the team, comprising scientists from the California Institute of Technology, HP Labs and the University of Washington, the device could act as the 'building block for future quantum networks'.
This device – described in the New Journal of Physics – combines a nitrogen vacancy centre in diamond with an optical resonator and an optical waveguide. A nitrogen vacancy centre is a defect in the lattice structure of diamond, where one carbon atom is replaced by a nitrogen atom and the nearest neighbour carbon atom is missing. The phenomenon has the property of photoluminescence – it can absorb and emit photons.
The emitted photons are special in that they are correlated, or entangled, with the nitrogen-vacancy centre from which they came; the tream says correlated photons cannot be generated by a normal light source.
In the proof of concept device, the nitrogen-vacancy centre is located inside the diamond resonator and a cotton bud shaped waveguide sends the photons out in the desired direction through gratings at either end. The device is etched in a 300nm thick diamond membrane.
"One of the Holy Grails in quantum photonics is to develop networks where optical quantum emitters are interconnected via photons," said CalTech's Professor Andrei Faraon, lead author of the study. "In this work, we take the first step and demonstrate that photons – information carriers – from a single nitrogen-vacancy centre can be coupled to an optical resonator and then further coupled to a photonic waveguide. We hope that multiple devices of this kind will be interconnected in a photonic network on a chip."
In their study, the researchers tested the device by cooling it to temperatures of less than 10K and shining a green laser onto the nitrogen vacancy to evoke photoluminescence.
"The whole idea of these devices is that they are able to be produced en masse. So far, the procedure for mass fabrication is still at the proof of concept level, so there is still plenty of work to be done to make it reliable," Prof Faraon noted.
