Usually, there are many ways to solve a problem. Some times, there is only one. Take the recent Nature Materials paper in which researchers at the Los Alamos National Laboratory in collaboration with the Quantum Sensing Lab at University of Basel present a new source of chiral quantum light. Such circularly polarized photons have become highly sought after, for example, to enable quantum information networks.
Existing methods to produce chiral quantum light highly depend on an external magnetic field that ensures emitted photons assume a circular polarisation. The setup developed by the Los Alamos groups didn’t. They employed a novel combination of the two-dimensional atomically thin material tungsten di-selenide (WSe2) and an underlying layer of antiferromagnetic nickel-phosphorous tri-sulfide (NiPS3), both having a thickness of an atomic monolayer only. Using an atomic force microscope, they then created nanoindentations – little dimples – on the substrate. By directing a laser at the dimples, they were able to produce a continuous stream of chiral quantum light.
How did this work in the absence of a strong external magnetic field? The researchers reasoned that the nanoindentations deformed the antiferromagnet (which nominally does not produce an external magnetic field ) in a way to give rise to an “exchange field” that, at least locally, was strong enough to lead to circularly polarized photon emission from WSe2. All they needed was a way to confirm their hypothesis.
The solution – NV Magnetometry
According to Patrick Maletinsky (Professor at the University of Basel, CSO and Co-Founder at Qnami) there is currently only one experimental technique sensitive enough to directly demonstrate the emergence of such weak magnetic fields from a single NiPS3 indent: NV magnetometry. That’s why he was happy to help the team at Los Alamos when they reached out to ask for advise.
“The signal we were after was at the edge of detectability and only barely came out against the noise. But after lots of control experiments and double-checking, we were very excited to confirm that it was, in fact, there. At the same time, we further demonstrated the capacity of NV Magnetometry to be used at cryogenic temperatures,”Patrick Maletinsky, PI at the Quantum Sensing Lab (University of Basel) and CSO and Co-Founder at Qnami
Congratulations to all the researchers involved in the study: the groups led by Scott A. Crooker and Han Htoon at Los Alamos National Laboratory, and their collaborators from the University of Basel led by Patrick Maletinksy.
Read more about the study on our application page.
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