Quantum physics is the science of the nanoscale (a nanometre is a billionth of a metre). At this scale, energy can only exist in discrete "packets", called quanta.

QUANTUM STATE

Physicists refer to the "state" of a quantum system, such as an electron. This describes an object's location, momentum, charge, wave form, "spin" (magnetic polarity) and energy level.

STRANGE BEHAVIOUR

Scientists working on the quantum physics revolution want to exploit the strange behaviours that matter exhibits at the nanoscale.

At the macroscale, matter exhibits the property of particles bouncing around, however at the nanoscale, matter acts more like waves and this means things get weird.

1. Superposition

Quantum systems, such as photons or electrons, exist as probabilities. The wave-like structure means that an electron might exist in various locations.

And because matter at this scale behaves like waves, when subatomic "particles" interact they "interfere" with each other, like ripples on the surface of a pond, or sound waves coming from separate speakers.

The result of this is that quantum objects can effectively be at two places at the same time, but this cannot be directly observed – see uncertainty below.

Application: Used as the basis for quantum computing systems.

2. Uncertainty

Intimately related to superposition is the effect described by Heisenberg's uncertainty principle. Specifically, the more precisely we know a quantum object's position, the less precisely we know its trajectory – and vice versa.

As a consequence the quantum "state" of these objects cannot be known unless it is measured. And until that point the object exists in all of its possible quantum states. The act of measuring the object means that the object "collapses" into one of these possible states and it is that state we measure.

Application: Quantum sensors: the limits of measurement described by quantum mechanics will soon be used by the Laser Interferometer Gravitational-Wave Observatory (LIGO) detector that recently confirmed the existence of gravitational waves, increasing its sensitivity.

3. Entanglement

Perhaps the strangest quantum property of all. Einstein dismissively called it "spooky action at a distance". Entanglement occurs where elements of a quantum system – such as their "spin" – are dependent on each other. It occurs when the quantum state of one object is necessarily the opposite of another object. Switch one, and you switch the other – instantly – even if they are at a distance. This is the basis of what is sometimes described as "quantum teleportation".

Application: Encoded data systems can use entanglement for communication protocols that are 100 per cent hacker proof.