Updated: Mar 25
Quantum computers are a strange and foreign concept for most of the world. You might see them as a silly conception that tech-obsessed nerds seem to rave about, or maybe you think they have the power to cure cancer, but they’re both of these things and neither. Quantum computing is hard to explain because it works on an entirely different level of physical mechanics than we are used to– in the atomic and subatomic properties, also known as quantum physics. As you may know, the atom is the smallest unit of any physical property and is just what quantum computing tries to integrate with. Qubits are known as the basic unit of information in a quantum computer; you may relate this to classical computing where information is represented in ‘bits’ where each bit is awarded a singular value of either 1 or 0. What makes a qubit special is that they can exist outside of this cage of 1s and 0s, and instead hold a mixed ‘superposition’ of both possible states. To put it simply before I discuss the various aspects of these machines, a quantum computer is simply that of one able to harness the behavior of quantum physics which simply can’t be accounted for with traditional computers.
To begin, let me introduce the first property of quantum computers which is entanglement. Entanglement is the ability of quantum particles to correlate with one another. This is the phenomenon where two particles are generated such that their quantum states are indefinite until measured, and the act of measuring one determines the result of measuring the other no matter the distance from each other. In the quantum computer, the qubits are these particles that can form a single system and thus influence one another. Entanglement allows qubits, which behave randomly, to be exactly correlated, and using algorithms, quantum entanglements can be harnessed to solve complex problems much more efficiently than classical computers. For example, with an algorithm created by IBM known as Grover’s Search, they tested that you supposedly needed to find one item in a list of N items. For one item in a list of a trillion, the classical computer would take up to a week in contrast to the quantum computer which would take merely a second.
The second concept to talk about is superposition. Qubits alone are not particularly useful; they act randomly and are hard to understand. However, one aspect of them and quantum particles, in general, are that they are a combination of all possible states, meaning they fluctuate in between the known 1s and 0s of a classical bit until they’re observed and measured. A classic way to understand this difference between a traditional bit’s fixed position and a superposition is to imagine a coin. If you flip the coin, you’ll get head or tails. However, if you can look at the coin and see both head and tails at the same time, as well as every state in between, that coin would be in superposition. This state of superposition is extremely useful because qubits can be connected and form vast computational networks that can represent complex problems using programmable gates. However, building a functional quantum computer is difficult because they require the ability to hold a qubit in superposition long enough to carry out various processes, and as soon as a superposition meets with a measured or observed system, it loses its in-between state and collapses to a regular bit.
In general, quantum computers are fit only for some of the complex tasks that traditional computers physically can’t compute or would not be able to nearly as quickly. However regular computers are still much more practical and usable for most tasks. Quantum computers are important where supercomputers with thousands of CPU and GPU cores fail, which is with certain complex types of problems that may seem initially easy such as Grover’s search. So the takeaway is that quantum computers can’t do everything faster than classical computers, but there are areas where they have the potential to make large impacts such as modeling quantum systems, cryptography, optimization, and quantum machine learning. So really, quantum computers are not these magical entities and they are not supreme to our traditional computers at least for the time being.
Written by Mariah