Basic Guide to Quantum Computing and Superposition
Over the past few years there has been a lot of buzz around the development of a quantum computer. I have heard the phrase quantum computing, but I’ve never been sure what the benefits of a quantum computer would be and how it worked. The world of quantum mechanics is extremely complex and confusing so for this post I decided to focus on understanding superposition, which seems to be where everyone starts when trying to explain quantum computing. I am by no means any sort of expert on quantum computing and am including all the resources I read at the end of this post for anyone who is interested in reading deeper into the topic. I will do my best to provide a very simple explanation of superposition and the potential benefits the quantum computer could provide.
Superposition
One of the main differences between classical computers and quantum computers is the use of the qubit. The computers we are accustomed to use bits, which is a binary digit that can either have a value of 0 or 1. A qubit can be any two level quantum system, such as a spin in a magnetic field or a single photon. Similar to a bit, a qubit has a possible value of 0 or 1. However, in the quantum world a qubit can be in both states at once (superposition). The wikipedia definition of quantum superposition states, “any two (or more) quantum states can be added together (“superposed”) and the result will be another valid quantum state; and conversely, that every quantum state can be represented as a sum of two or more other distinct states”. The two states in this definition for the qubit are the 0 or 1 values a normal bit can also have. Basically, before a qubit is observed it is in a superposition of probabilities for 0 and 1. A great example to help explain this is to picture a coin being flipped vs a coin being spun. If you flip a coin it will land on either heads or tails (bit). However, while a coin is spinning you can say the coin’s state is both heads and tails at the same time (qubit). The catch is that once a qubit is observed it will take of the state of either 1 or 0. The video below does a much better job explaining how a qubit works and helps explain superposition.
What are the benefits of a qubit?
The graphic to the left shows the impact of the qubit vs the bit. Since a qubit can be in the state of both 0 and 1 at the same time the amount of classical information contained by N qubits is equal to 2 raised to the power of N classical bits. Due to this quantum computers excel at optimization problems. They are very skilled at solving problems where there are an exponential amount of permutations to try out. An article from Tech Republic states, “If you had a 2^100 problem, which would be basically impossible to solve on a classical computer, with a 100-qubit quantum computer, you’d be able to solve it in one operation.”
Real Life Uses of the Quantum Computer
As I mentioned above, quantum computing makes it easier to solve problems with a large amount of permutations. This makes it extremely useful for cracking encryptions. For example if you are sending credit card information to an online store the retailer will send a long string of numbers that is the result of two prime numbers multiplied together. Your computer will scramble these numbers so anyone trying to steal the info will not be able to read it. A traditional computer would not be able to go through all the possible combinations of prime numbers in a reasonable amount of time. However, a quantum computer would be able to solve this problem much more easily. In 2014 the Washington Post had an interesting piece on quantum computing and how the NSA could use the increased computing power.
Another really cool use of quantum computing is for simulations. Per wired, in 2016 Google used a quantum device to simulate a hydrogen molecule and IBM has modeled complex molecules as well. Researchers believe they can use quantum simulations to design completely new molecules to be used in medicine.
Below are a ton of resources to go deeper into the basics of quantum computing.
