## What is Quantum Computing?

What happens if you throw a tennis ball at a brick wall?

What if you through a hundred tennis balls at the wall at the same time?

What if you through a thousand tennis balls?

*Nothing*.

No matter what you do, there’s no way tennis balls are going to break down that brick wall. Just like a brick wall, there are some problems that are so complex that there’s no way a traditional computer, no matter how fast, can solve them.

But what happens to the brick wall if you drive a tank through it?

*No more brick wall.*

That tank is a quantum computer.

**Bits and Qubits**

Classical computers, the kind we use every day, use memory made up of bits. Bits represent either one or zero; on or off. Everything computers do, from playing games to sending email, comes from manipulating those ones and zeros.

A quantum computer is a new type of computer that uses the unusual properties of quantum physics to solve problems that are impossible for regular computers. They do this by using qubits instead of bits. Like bits, qubits can represent a one or zero. What makes them special is that a qubit can be one, zero or a superposition of both. That means that a qubit can be both one and zero at the same time – making quantum computers exponentially more powerful than their conventional counterparts.

**Breaking the Brick Wall**

By using superposition, quantum computers can solve problems that would be impossible or take thousands of years to complete. Quantum computers dramatically outperform classical computers in calculations involving large numbers of equally possible solutions.

Because of their strength at analyzing combinations, quantum computers will most likely be applied to breaking codes and optimizing complex systems. Researchers also expect that quantum computers will be able to accurately model events at the molecular scale, providing a powerful tool for biology, chemistry, and physics research.

**Problems and Predictions**

Superposition is powerful, mysterious and delicate. The biggest barrier to building fully functioning quantum computers is that qubits must be held in a super-cooled, isolated state or they decohere and loose their quantum “magic.”

Quantum computers are sitting at the edge of practicality. Developers have successfully constructed working quantum computers, but so far have been unable to get enough qubits working at the same time to realize their full potential – but the promise of that potential has scientists all over the world working on making quantum computing one of the defining technologies of the 21st century.

For more information see the NEC Laboratories [http://www.nec.co.jp/rd/Eng/innovative/E3/top.html] website.

For information about the first private quantum computer, see the CBC report on D-Wave Systems.