THE QUANTUM CONUNDRUM WHAT AN ENTANGLED MESS WE WEAVE…

Forget material science, feature density, and all that oldfashioned stuff involving classical physics and chemistry. Could quantum computing make Moore’s Law completely redundant, but in a good way?

According to quantum computing advocates, it’s possible to imagine a single quantum computer capable of not just matching the combined number-crunching might of all existing classical computers, but also of executing as many calculations at once as is practically useful. In other words, all the computing power any of us could ever need in a single machine. Forget Bill Gates’ apocryphal claim that nobody needs more than 640K, quantum computing aficionados think we won’t need more than one PC between us.

If that sounds like a fringe theory, try this comment from Android OS architect Andy Rubin. “If you have computing as powerful as this could be, you might only need one [computer].” So, how might that work? Conventional computing operates in the binary realm of zeros and ones, otherwise known as bits in computing vernacular. The basic component in a classical computer, the transistor, is therefore either off or on. There is no alternative.

With quantum computing? Not so much. Thanks to a quantum phenomenon known as superposition, which applies at the atomic and sub-atomic scale, it’s possible for a quantum computing bit to be not just both on and off at the same time, but also a huge array of hybrid superpositions somewhere in between on and off. This is a qubit and it is the basic building block of quantum computing.

The other important weirdness of quantum computing, and arguably the factor that makes things exciting, is entanglement. It’s a notion even tenured physics professors struggle with. But the basics involve the idea that the quantum properties of two or more particles can be inextricably linked regardless of any distance between them. Change the spin of one particle, for example, and others instantly react.

The trick to achieving powerful quantum computing, therefore, is to ‘entangle’ multiple qubits. Quantummechanically link or entangle two qubits and you can perform two calculations simultaneously. Link three qubits and the math of quantum entanglement means you can do two to the power of three—or eight—calculations. Link four and you can perform 16 calculations simultaneously. Follow that logic and by the time you have 300 entangled qubits, you can perform more calculations in parallel than there are atoms in the known universe. Handy.

The catch? There is doubt that a quantum computer on that scale is possible due to the problem of quantum decoherence. Some argue the quantum state of the machine can’t be maintained long enough to do anything useful, but others question whether quantum computers can be applied to general computation at all, and instead will always be limited to irrelevant, esoteric math of little practical benefit. Unfortunately, we forgot to polish up on our applied physics PhDs here on MaximumPC, so all we can say is time will tell.