In 1927, at a conference in Brussels, a new theory burst onto the scene. The literati of the day’s theoretical physicists had gathered to hammer out an accurate description of the nature of matter on the scale of the very small. The result, a mathematical depiction of the way subatomic particles interact – quantum mechanics – was forged in a fiery series of debates that raged between the likes of Einstein, Bohr, Heisenberg, Schrödinger, and so on. This ushered in the first quantum revolution, which led, amongst other things, to the invention of the transistors that powered our circuit designs into the electronic age.
We are now in the midst of a second quantum revolution. A time where the scientists and engineers of our generation are developing an ever more powerful array of technologies based on the rules of quantum theory. Although quantum computing currently hogs the publicity, the area of sensors may turn out to be just as fertile. Due to their quirky nature, quantum states have a sensitivity that can be used to detect tiny variations in local gravity and magnetic fields. This paves the way for a new generation of ‘quantum sensors’ that are orders of magnitude more precise than anything we have available today.
One of the payoff applications for quantum gravity sensors is detecting signs of buried infrastructure from above the ground. While conventional methods for doing this already exist, they are limited in their sensitivity and prone to the influence of shielding effects from underground rocks and moisture. Gravity is immune to such shielding since it is generated by mass, so any object with a density different than its surroundings will result in a tiny change in the local force field. Due to their extraordinary sensitivity, quantum sensors are able to pick up these otherwise undetectable fluctuations. Once perfected, such sensors could open up a whole new range of possibilities in the fields of underground exploration and the monitoring of seismic activity.
On the magnetic front, a quantum probe that scans the human brain in minute detail is one of the more intriguing areas of research at the moment. Brain scans are not new of course, but what is new is the astonishing degree of precision (down to the cellular level) that such quantum probes offer in the examination room.
The new optimism around quantum technology is that we are still so far away from any theoretical limits. Before we can start to capitalise on this though, there is the small matter of perfecting a way to keep the sensing atoms in a quantised state. Since atoms are so tiny, even miniscule amounts of extraneous energy can upset their delicate balance and cause their wave functions to collapse into something definite. Commercialising the mass production of quantum sensors is the challenge a number of companies have put on their to-do lists and reports indicate they might soon bring their first products to market. In the meantime, the sensing technology we have at our disposal today is still pretty darn impressive. See this month’s sensor and transducer feature on page 36 for the latest applications.
Steven Meyer, Editor: SA Instrumentation & Control, [email protected]
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