Quantum Sensing Made Simple

As the years go by, more and more developments are being made in the field of quantum sensing technology. But what is quantum sensing? As with many emerging areas of physics research, a google definition will yield a string of acutely selected, rigorously precise and yet somewhat incomprehensible jargon aimed at the motivated academic. Here I will heroically aim to break it down to the layman using my expert credentials (undergraduate student that took a course in quantum physics once).

https://physicsworld.com/a/quantum-sensor-survives-at-record-high-pressures/

Starting off with the notion of sensing. Very simple. In physics we do experiments, and experiments involve measurements. Beyond a foundational level of investigation usually these measurements are recorded by a piece of equipment that “senses” something. Maybe it’s an x-ray diffractometer sensing the intensity of a scattered beam. Maybe it’s an oscilloscope sensing the voltage transient of a nanowire. Doesn’t matter. Point is, some of the things that need to be sensed in physics experiments are quite complicated, especially when the required resolution is on a tiny scale like the nanoscale, i.e. the scale of one billionth of a metre. Things like magnetic fields, electric fields, and the motion of tiny particles fall into this difficult category for sensing. So of course, being the fidgety, never satisfied bunch that they (we?) are, the physics community set out to make advancements in sensor technology so these properties could be analysed more thoroughly. That’s where the dreaded Q word comes into play.

When light famously came out as Dual in 1905, announcing that it liked being a wave *and* a particle, it influenced a number of its peers to admit they hadn’t quite been their true selves either. Wavefunctions opened up about BPD (Being Periodically Decoherent), whereby time spent apart from their other half occasionally resulted in falling out of step in certain environments. Their entanglement was however unbreakable and they eventually developed a coping mechanism with Quantum Spin, which allowed them to collapse simultaneously if put under too much scrutiny.

https://bigthink.com/starts-with-a-bang/quantum-entanglement-weirder/

Where am I going with all this? The point I’m framing really is that in some ways, the introduction of quantum mechanics complicated everything, but it is those complications that arose from it (decoherence, entanglement, and interference are but a few and to understand them fully you would need to look beyond the scope of this blog post) that are actually utilised by quantum sensing devices. The scientific community always finds a way to turn these nightmarish phenomena into forces for good. The most interesting part however is some of the methods used to create quantum sensors. My personal favourite and a very popular area of research at the moment concerns diamond vacancy centers. Far from being an office that unemployed diamonds can visit to seek employment as the name suggests, this actually refers to the practice of removing carbon atoms in the structure of diamond samples and adding a different atom, which is usually nitrogen but others including tin vacancies have also been used in quantum sensing.

https://www.sciencedirect.com/science/article/pii/S0079656516300462

All well and good but what do they actually do? The first main application was in something called single photon emission (quite self explanatory), which allows for quantum cryptography (fancy word for data protection using the properties of quantum physics. Diamond quantum sensors are therefore of a lot of use in computing technology. Many other applications arise from the behaviour of the vacancy centre as an atomic-scale magnet, rendering it capable to measure magnetic fields to an astonishing degree of accuracy. It’s actually quite hard to comprehend the level of advancement made by quantum sensing technology, diamond or otherwise, to numerous fields within physics, computer science and even biomedical sciences. I highly recommend an afternoon going down the rabbit hole of the web to learn more. Feel free to comment your findings here!