Qubits

There are 10 types of people in this world: those who know binary and those who don’t.

 

If you don’t get that joke, I suggest you read up on how binary works, because binary isn’t just a cool thing to know anymore. Practically every human alive today will interact with a computer at some point in their life. While it appears that computers understand our languages, that’s just a facade. The language of computers is binary: long endless streams of 1’s and 0’s.

As mentioned in the last video, computers process these 1’s and 0’s with transistors. The more transistors you have, the more operations you can do in parallel, equaling faster computing speed. But, eventually we will reach a limit on the number of transistors we can hold on a chip. At that point, what will be do?

The traditional system of storing information uses bits, each bit being a 1 or a 0. Supposing I had two bits, I have four different combinations: 00, 01, 10, and 11. Each combination represents exactly two bits.

Now, let’s bring in some quantum mechanics. Scientists are working on developing new types of bits, known as qubits (quantum bits). Like classical bits, the have two positions: up and down. However, these qubits can exist in superpositions, where we don’t know whether it is up or down. Essentially, it is both up and down, and we only have probabilities two predict which position it is in. That’s pretty cool, and something that takes time to wrap your head around!

Now imagine I had two qubits in superpositions. There are still four possible combinations: DD, DU, UD, UU. However, we don’t know which position each qubit is, so instead the information is represented as probabilities of each combination. That means two qubits conveys four classical bits of information. \

Scientists have found that n number of qubits convey as much information as 2ⁿ classical bits. At first, that doesn’t seem like much of an improvement, but once you start thinking of having 300 or 400 qubits, the numbers get impossibly large for a human to comprehend.

By requiring a lesser number of operations, qubits can work faster than classical computers. But is that the end of the story? Are qubits a universal substitute for classical computers? We’ll look into that in the next post.