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What Is Quantum Computing?

Everyday Einstein chats with Tech Talker about quantum computers. What are they and how can they change our world? Click to read or listen.

By
Lee Falin, PhD,
December 7, 2013
Episode #079

Page 1 of 2

This week I’m teaming up with Tech Talker to discuss quantum computing.

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First off, just what makes a quantum computer a quantum computer? I’ll let Tech Talker explain:

Tech Talker: It's quantum...duh! Okay but seriously, a normal computer uses bits (1's and 0's) which are generally stored on transistors. Normal computers use bits to execute code, store pictures, play music, check Facebook, and pretty much everything you can think of. Quantum computers store their information as Qubits or Quantum Bits. Quantum bits are pretty tricky, because they can be a 0, or a 1, or both!

This allows for some pretty exciting things in the world of programming and mathematics.

Everyday Einstein: What allows quantum bits, or qubits, to behave this way is something called superposition, which is one of the key principles behind the idea of quantum computing. A common object that we use as an example when we discuss superposition is the electron. Electrons have a property called spin, which can be either up or down. However, according to the theory of quantum mechanics, not only can an electron spin up or down, it can also have a spin that is any linear combination of those two states. A linear combination means that it's a little of the up state plus a little of the down state.

Where things get strange is that while one observer may see the electron with an up spin, another observer might see the electron with a down spin. The fact that these differences of measurement occur, even though both observers are looking at the electron at precisely the same moment, means that in quantum mechanics we consider the electron to have both of these spins at the same time. We call this property superposition.

This is important for quantum computing because, as Tech Talker said, normal computers use a bit which can either be 1 or 0. So if you have an 8-bit computer, it can have 1 out of 2 to the 8th power (or 256) at any given time. However a quantum computer taking advantage of superposition could be in all 256 of these states at the same time. That means that for certain types of algorithms (though not all), quantum computers could cause an enormous increase in computing power.

So what exactly is a qubit?

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