What is a quantum computer?

A quantum computer is a processor which relies on the principle of quantum mechanics to perform complex calculations at speeds unattainable by classic computers. By harnessing principles such as entanglement and superposition, they can process vast amounts of data and can become powerful tools in fields such as cybersecurity and AI.

How does it work?

Classical computers use bits, either 1 or 0 to represent binary states. In contrast, a quantum computer uses qubits. These qubits can exist in an in between state of both 1 and 0. This is called superposition and means that a qubit can represent many differents states at once and allows a quantum computer to explore many different potential solutions simultaneously.

If all this seems a little bit confusing, a simple analogy is the tossing of a coin. When flipped, a coin has two possibilities: heads or tails: 1 or 2. However, while the coin is still in the air, there is still the possibility that it could be either 1 or 2 and is therefore there is the parallel existence of both outcomes until measured. This is the same with a qubit, it exists as both until measured and put into a definite state.

What is entanglement?

As the name suggest, entanglement is when two states are tied together no matter how far apart the objects may be. In the example I will use, the state will be whether a shoe is a right or left foot. Imagine you had a pair of shoes which have been put in a box together and therefore are entangled. If you randomly pick one of the shoes, you must instantly know that the shoe in the box is for the other foot. Now imagine that you separate them and randomly fly one box to Mars. If you open the one on Earth and see a left shoe, you must again instantly know that the box on Mars has the right shoe. This phenomenon was labelled by Albert Einstein as “spooky action at a Distance.” Quantum computers are able to entangle 2 qubits so that their measurements are correlated. This entanglement allows several qubits to be manipulated as a single system, making the computer more efficient at certain calculations.

Supercomputer vs. Quantum computer

Because quantum computers have a superposition state, they are able to explore many different solutions at once. A quantum computer is not universally faster than a classic supercomputer, it is just that it can open the possibility of more computations at once than a supercomputer, allowing it to excel at certain tasks such as factorising large numbers. However, quantum computers can lead to inaccurate solutions because environmental noise and vibrations can upset superposition and entanglement. For this reason, there need to be additional error identifying systems in order to combat inaccuracies.

In what fields can quantum mechanics be used?

Due to its vast processing power, quantum computers can lead the way into the future specific tasks in Cryptography, AI and Machine Learning and, material sciences. This is purely because of the way that they can crunch vast amounts of data with 100s of possibilities per operation.

Where is it today?

Quantum computing is still in its early stages, with research institutions and companies like IBM, Google, and others developing prototypes. These machines are limited in scale and stability, but significant progress is being made toward achieving practical applications. Today’s quantum computers are mostly used for experimental research rather than solving real-world problems, but advances in hardware and error correction are bringing them closer to broader use and hopefully we will see widespread use of them in the future.