Question: What is quantum physics?

Daisy Shearer answered on 24 Mar 2022: last edited 27 Mar 2022 9:03 am

TL;DR: Quantum physics is a branch of physics that mostly deals with really small things like atoms and electrons. We find that on these scales, we can observe that things like particles behave in some interesting ways. You may have heard of things like quantum tunnelling, quantum entanglement or quantum superposition. These are things that quantum physicists like me are interested in understanding and using to develop new technology!

More detailed answer:
Quantum physics is about understanding matter and energy on its most fundamental level. The word ‘quantum’ actually means ‘a discrete package of something’. From this, we get the word ‘quantization’ which basically means that rather than something being a continuous function, it comes in discrete packages. So a good analogy is the difference between a ramp and stairs: You can’t stand halfway up an individual step, but if it was a ramp you’d be able to stand at any height you wanted to. So in the case of stairs, the height you can stand at is quantized- it can only take certain values rather than ANY value like with a ramp.

A good example of this in physics is the energy of electrons. If you’ve learnt about atoms you’ll know that our current model has ‘electron shells’ which basically means that electrons can only occupy certain discrete energies within an atom rather than being able to take on any energy– they’re locked into these ‘shells’. Another example of quantisation is photons which are packages of light that have discrete energies and we can only explain experiments like the photoelectric effect using the model where we have discrete photons.

What’s interesting is that quantum phenomena are actually acting on everything, it’s just that it’s easier for us to see them on tiny scales because the bigger a system is, the less stable quantum states are (this is something called ‘decoherence’).

Some history:
Quantum physics has played a key part in developing our understanding of many fields such as physics, chemistry, materials science, biology and astronomy. As an idea, quantum mechanics arose in the late 1800s and since then has been vital in developments of technologies such as lasers (which we use to transmit data through the internet through optical fibres) and transistors (which make up most of our modern-day computers). Without developments in quantum physics, our world would look very different and I probably wouldn’t be able to type this to you today! Who knows what amazing technology we’ll be able to create as our understanding of quantum physics improves and develops!!