On the centennial of modern quantum mechanics, the Nobel Committee awarded the year’s most prestigious physics prize to an experiment that demonstrated how quantum effects play out on large scales—including inside your smartphone.
In fact, the implications of this year’s winner—quantum tunneling—stretch way beyond the device in your pocket.
John Clarke, Michel Devoret, and John Martinis conducted their initial experiments in 1984 and 1985, but their work has had a lasting impact, becoming “the foundation of all digital technology,” Olle Eriksson, Chair of the Nobel Committee for Physics, said in a statement.
But what is quantum tunneling, and how has it brought this bizarre realm of physics into our everyday devices? Read on to discover why this quirk of quantum is so critical.
Quantum tunneling, the basics
Imagine throwing a tennis ball against a wall. Millennia of both scientific and anecdotal observations teach that the ball will likely hit the wall and bounce back. In the quantum world, however, that isn’t always the case. There, the ball might pass straight through the wall and appear on the other side—a phenomenon referred to as “tunneling.”
Size is a tricky concept in quantum mechanics, but very simply speaking, “microscopic” scales in this context generally refer to that of a single particle. By contrast, “macroscopic” refers to a large number of particles. Quantum mechanical effects appear to fade on the macroscopic scale, hence why a tennis ball—comprised of a gazillion particles—typically doesn’t pass through walls.
But the Nobel-winning experiment created a highly sophisticated, superconducting circuit that enabled electrons inside to move through the system as if they were a single particle, filling the entire circuit. The electrons in the system tunneled through a thin layer of non-conductive material—and thus, the circuit, which the researchers had described as being “big enough to get one’s grubby fingers on,” is a macroscopic demonstration of a microscopic, or quantum, phenomenon.
The quantum in your smartphone
To be clear, superconducting devices aren’t here yet. But the chip in your phone, while being a semiconductor, not a superconductor, still utilizes the lessons from the tunneling experiment to work. As do transistors, nuclear experiments, and, of course, quantum computing.
Tunneling taught engineers how energy leaks from very-large-scale integration, the process from which we get complex semiconductor transistors and chips. Specifically, tunneling represents a “physics limit” for the minimum size of a feature on a chip.
Scientists have also applied principles from quantum tunneling to make next-generation solar cells, while scanning tunneling microscopes—instrumental in several physics breakthroughs—were also built on the concept of quantum tunneling.
Tunneling is also considered a vital part of any nuclear fusion experiment. For fusion reactions to succeed, the individual particles need to overcome their natural tendency to repel each other—by harnessing tunneling, physicists have been able to find some leeway around this obstacle.
Not all of these applications are immediately apparent. Clarke, one of this year’s physics winners, admitted during a press conference on Tuesday to being “completely stunned,” as it had “never occurred to me in any way that this might be the basis of a Nobel prize.”
Still, there’s no doubt that this Nobel-winning work perfectly demonstrates the remarkable presence of quantum mechanics in our everyday lives—just in time for the International Year of Quantum!
To quote Nobel Physics Committee Chair Eriksson: “It is wonderful to be able to celebrate the way that century-old quantum mechanics continually offers new surprises. It is also enormously useful.”