If you lived according to quantum laws, you could pass ghost-like through solid objects, become one with other entities, or exist spread out over all of space at once. Sadly, solid walls are impervious to us; we can get close to other people but never truly blend into one being; and we may grow throughout our lives, maybe even a bit more than we’d like, but we will never know what it’s like to occupy more than a couple of cubic meters of space at a time.
Although the weirdness of the quantum world is almost unbelievable, scientists have proven time and time again that counterintuitive quantum laws govern the realm of molecules, atoms, and subatomic particles. We and everything we see around us, on the other hand, follow the familiar rules of so-called classical physics despite the fact that, at some level, we are made of quantum pieces.
How do we reconcile the two worlds? How, as we zoom out from the very small to human scales, do we transition from quantum to classical rules? What happens on the brink of the two worlds as we move from one to the other?
Those questions have irked and entertained scientists since quantum mechanics was discovered nearly a century ago. The answers have been debated and argued in research papers and conferences ever since. One potential way to understand the intersection of the two worlds is by building a quantum device to directly observe the transition between the quantum and classical worlds with our classical microscopes, cameras, and even our eyes.
Researchers at Los Alamos National Laboratory have developed a prototype that may soon allow us to do just that. The Superconducting Quantum Interference Device (SQUID) is only a fraction of the diameter of a human hair, but it’s much larger than most things that follow quantum laws. Unlike atoms and individual molecules, the SQUID is potentially visible under a microscope, and the research team expects to make bigger versions in the future.
Electronic SQUIDs are common in medical imaging machines and other applications that rely on sensitive magnetic sensors. They detect changes in magnetic fields by monitoring the flow of electric current in a loop. Conventional SQUIDs are sensitive to the very smallest magnet field quantity allowed by quantum mechanics. Although circuitry of electronic SQUIDs can be large enough to see with the naked eye, the quantum interactions involve invisible magnetic fields and electric currents inside wires.
The Los Alamos atomtronic SQUID, on the other hand, relies on clouds of super-cold atoms trapped with laser light, instead of electric currents inside metal. That means one could potentially watch quantum interactions as they play out by observing the atom clouds in motion.
The individual atoms in an atomtronic SQUID obey quantum rules, including the ability to blend together to become a single cloud-like entity, which in turn follows quantum rules. There’s no limit to how many atoms can come together this way, which means that we can make very large blobs of atoms that are potentially both visible and quantum mechanical at the same time. The result is something that exists simultaneously in the weird quantum world and ours. Just what that will look like isn’t yet clear, but it will potentially help solve the mystery of how everyone and everything around us are built of quantum pieces although we live a distinctly non-quantum existence.
Practically speaking, the atomtronic SQUID is extremely sensitive to motion, so it could provide a new way to navigate without GPS — a blessing for travelers who lose signal in cities, tunnels, or other places that GPS satellite signals can’t reach. This is just the first of what is likely to be a whole class of things that harness quantum rules to our benefit. The field is still so new that it’s not clear what those things might be at the moment. It’s possible, though, that devices relying on quantum weirdness will be as common as smartwatches in the not-to-distant future.
Just don’t expect to glide through walls … yet.