Sunday, October 28, 2012

Quantum Computing 101 - Part 1

“I think I can safely say that nobody understands quantum mechanics.” - R. Feynman (1965)

The strange and wonderful world of quantum mechanics will be the main topic of my first series of blogs. First, I’ll start off with quantum computing, followed by more general topics in quantum mechanics like Schrödinger’s cat. But first, let me start with some basics.

What is the difference between a “normal” computer and a quantum computer? Computers nowadays are based on transistors and handle information using binary bits. These bits can have values of either 0 or 1. Every text or image file is encoded using only 0 or 1. In contradiction, a quantum computer operates using so called qubits (quantum bits). A qubit must have two states, 0 or 1 as well. However, in addition they can also be in a superposition of both, that means in both of them at the same time. You could think of a qubit as an electron. An electron is rotating along it’s axis, which is called spin. The electron’s spin is either directed upwards (spin up) or downwards (spin down). The up or down state is now acting as your 1 or 0. As previously explained, this qubit can also be in a superposition of both.

Why are quantum computers so powerful? The principle of superposition can be scaled with the number of qubits. A computer with two qubits can be in a superposition of 4 states, whereas a classical computer can only be in one of it’s 4 possible states. Because qubits can be in a superposition of both states, the state is rather presented by a probability. There is a certain probability you can find the electron in either of these states. With that you can enhance current processing speeds enormously.

Are their any commercial applications of quantum computing yet? In 2011, a canadian based company, called D-Wave started selling the first commercially available quantum computer. It features a 128 qubit processor which is housed in a cryogenic system. Earlier in 2009, Google demonstrated the use of D-Wave’s technology for image recognition. This brings us a big step forward, however, with a cost of $10,000,000 it’s still a bit pricy for the everyday use.

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