Qubit

A qubit is an object that can hold quantum information. This can take many forms such as electrons and nuclear spins, molecules, mechanical oscillators, photons, and many more. All an object needs to have to be considered a qubit is the ability to hold quantum information. But what is quantum information and what does it mean to hold it?

Quantum information

A classical information bit can only exist in two states: 1 or 0 (the same as true or false). Quantum information exists between these two states. This is the idea that something can be a superposition of the two states, meaning that it is both 1 and 0 at the same time. The quantum information stored in this fashion is incredibly useful for quantum computing but it is also important for many other reasons.

Why do people care?

Most people will say that people care about qubits and quantum mechanics because of quantum computing. However, quantum mechanics is far broader than this small topic and qubits are used in many different scientific and engineering research and products. This is because as soon as something gets small enough it becomes quantum, whether we like it or not. A significant amount of the nanofabrication done in the world is focused on quantum related objects because smaller is faster and more energy efficient. This doesn't mean that they are using qubits but it does mean that they need to consider the quantum nature of the object in order to get the desired results. Even medical research is starting to rely on quantum mechanics to determine how best to administer drugs or in attempts to probe the mechanics of how the human body works on the smallest scale.

People care about qubits because they are fundamental to quantum mechanics and it is required for us to understand anything about the world on a small scale.