COMPUTING WITH QUANTA

LET’S TANTALIZE ourselves with a peek into the bizarre world of quantum physics, where an entirely new kind of computer offers capabilities unbelievably beyond those of today’s most sophisticated digital machines. What’s more, some say quantum computers are only five years from commercialization.

“Quantum Information Processing” is the title topic of Science magazine, 8 March 2013. However, to attempt more than just a peek at these articles, we would have to wrap our minds around non-Abelian quantum Hall states, microfabricated ion traps and quantum error correction, not to say complex numbers (that is, a + bi, where i² = -1).

No, thanks. A peek into the quantum world will be quite enough.

The digital world accomplishes a great deal with binary values, 0 and 1.

Stripped to its basics, a digital computer counts on two fingers, albeit very quickly. Its basic units are 1 and 0, on or off. By contrast, the basic unit of a quantum computer is a quantum bit, or qubit, a two-state system of physical properties occurring on the atomic level.

A contrast of digital versus quantum computing.

Oddities of the quantum world abound, “superposition” and “entanglement” among them. A qubit’s two states aren’t simply on or off; they can be any combination or superposition of these at the same time. For instance, a subatomic particle like an electron possesses a range of energy levels simultaneously.

What’s more, when two particles interact physically and then are separated—even arbitrarily far apart—their measured properties are entangled. For instance, if two electrons interact and then are separated with one measured as having clockwise spin, then the other will have counterclockwise spin. Other subatomic properties have similar correlations.

In one of the Science articles, its two researchers, C. Monroe and J. Kim, say “In a sense, entanglement between qubits acts as an invisible wiring that can be potentially exploited to solve certain problems that are intractable otherwise.”

Quantum physics humor. Image from The New Yorker, February 1993.

Like a conventional computer, a quantum computer accepts data as input, employs internal programs or algorithms to process the data, and produces desired output. With the quantum device, input determines initial states of the qubits. These states are modified through controlled interactions called quantum logic gates. And the measured end-states of the qubits give the device’s output.

However, whereas digital computing is precise—and relatively slow—a quantum device’s algorithms operate probabilistically with incredible speed. In fact, a qubit’s state may be so ephemeral that it needs measuring before “decoherence” sets in. Error-correction processing solves the problem, to any desired high degree of probability.

One type of quantum processor uses trapped (i.e., controlled) atomic ions as qubits. The necessary hardware is elaborate indeed, with a vacuum chamber that’s super-cooled to near absolute zero.

How soon will any of this move out of the lab?

Two years ago, Lockheed Martin started looking at a quantum computer from Canada’s D-Wave Systems. Last week, March 21, 2013, Lockheed Martin announced that it’s incorporating quantum computing as part of its business activities.

Quantum computing hardware. Image from The New York Times, March 21, 2013, http://goo.gl/yJ6fJ.

Quantum computation will be used to engineer and test Lockheed Martin’s radar, space and aircraft systems. Millions of lines of software, for example, could confront a virtual solar burst, a simulation task that would take weeks or longer with conventional computers.

To put the capability of quantum computing in perspective, today’s gold standard for computer memory, the terabyte, stores 2⁴³ on/off values. Even a mere 100-qubit quantum machine could handle 2¹⁰⁰ complex values.

As Arthur C. Clarke so aptly put it, “Any sufficiently advanced technology is indistinguishable from magic.” There’s a great deal of magic in quantum computing. ds

© Dennis Simanaitis, SimanatisSays.com, 2013