Quantum dots with visible color frequencies. Image: Antipoff/Wikipedia
As we cruise through the 43rd year since Gordon E. Moore unleashed his famous prediction describing the future progression of microprocessors, those processors have hit a wall of sorts. That wall consists of two interrelated limitations: the nature of building with “things,” and the storing and processing of information using electrical charges.
When we see the potential of a single particle or pair of particles to capture a bit or qubit of information, just via their natural properties as quantum objects, the six transistors needed to keep hold of each single bit information in SRAM storage seems like cave painting, only with the added disadvantage of needing lots of continuous power to keep that paint from falling off the wall. This is the problem of building “things” to keep control of particles that are not quite things themselves, but are somewhere beyond.
In terms of information storage, spintronics suggests one solution to the memory problems of computers, but the fundamental strangeness of quantum mechanics offers so much more. One proposed future involves the use of quantum dots for our information movement/storage needs. A quantum dot is essentially a cage designed to hold a pair of electrons (or an electron-based quasiparticle called an exciton).
In the video below, that cage swapped out for a table. The two particles are repelled by each other, and in the captivity of a dot are forced into opposite corners of the box or opposite sides of the table. Using a magnet, it’s possible to scoot these particle pairs around their tiny quantum prisons and even use them to influence other captured pairs nearby. So, rather than maintain some information with electrical current, it’s possible to maintain it with basically no energy at all.
At the University of Alberta, Robert Wolkow and his team have moved beyond making computer components with "things." They’ve so far achieved both a quantum dot that's a single atom wide—which is being awarded a US patent this month—but also the world’s sharpest object, the tip of an electron microscope also a single atom wide (which is actually in the Guinness Book of World Records).
“It has the potential to totally change the world’s electronic basis. It’s a trillion-dollar prospect.”
In research released this week, the team describes new observations made of the surface features of those single silicon atoms, measuring precise charges and the electrical resistance across each silicon “step,” or the single-atom perturbations found on the surfaces of silicon crystals.
In what the Alberta team describes as a nanotechnology first, they were able to measure how many electrons might potentially fit on a given silicon atom, a feat previously deemed impossible for the simple reason that measuring something at the quantum scale changes it.
“It turns out that the quantum dot itself disturbs the nearby environment, so what we do is measure that disturbance,” Wolkow wrote in an email to Motherboard. “Imagine squatting underneath a trampoline. If someone stood on the trampoline, right over your position, the depression they cause might cause you to be hit in the head. You would have successfully detected someone on the trampoline, but you would also have limited how far they depressed the trampoline. So you perturbed the measurement.
“You might instead stand well off to the edge,” Wolkow continued. “You could measure the trampoline lowering—lesser distance—and even if it touched you a little, it wouldn’t much effect how far the person sunk into the trampoline. An electron in a quantum dot similarly, electrostatically, warps its surroundings.” As for getting the particles into and out of the dots, it’s a matter of applying different electric fields around the dots, effectively “tilting” the dot as if you were tilting a full bowl of water, pouring particles in and out.
Expect this technology in the world very soon. Wolkow and his team have their own commercial spin-off company, Quantum Silicon Inc. They estimate that within five or six years, these concepts will be finding real-world applications. At first they hope to add the technology to pre-existing circuits that are highly contingent on power usage, as might be found in GPS devices and satellites. But in ten years, QSI aims to have full atom-scale circuitry in mass production. Wolkow is optimistic, to say the least: “It has the potential to totally change the world’s electronic basis. It’s a trillion-dollar prospect.”