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If a time traveller went back in time and stopped their own grandparents from meeting, would they prevent their own birth?

That's the crux of an infamous theory known as the 'grandfather paradox', which is often said to mean time travel is impossible - but some researchers think otherwise.

A group of scientists have, for the first time, simulated how two time-travelling photons would interact, suggesting that, at a quantum level at least, jumping through time might be possible.

Researchers at the University of Queensland in Australia have discovered that two photons travelling through time can interact. In the simulation a photon stuck in a closed timelike curve (illustrated) through a wormhole was found to be capable of interacting with one travelling through regular space-time

The research was carried out by a team of researchers at the University of Queensland in Australia and their results are published in the journal Nature Communications.

The study used photons - single particles of light - to simulate quantum particles travelling back through time.

By studying their behaviour, the scientists revealed possible bizarre aspects of modern physics.

In the simulation, the researchers examined two possible outcomes for a time-travelling photon.

For the first, 'photon one' would travel through a wormhole into the past and interact with its older version, reports The Speaker.

In the second, 'photon two' travels through normal space-time but interacts with a photon that is stuck in a time-travelling loop through a wormhole, known as a closed timelike curve (CTC).

Simulating the behaviour of photon two allowed the behaviour of photon one also to be studied – and the results revealed that time travel on a quantum level seems to be possible.

By definition 'quantum' refers to the smallest possible particles that can independently exist - such as photons.

However, whether this same simulation proves time travel is possible for more larger particles or groups of particles, such as atoms, remains unclear.

In 1991 it was first predicted that time travel would be possible in the 'quantum world' because quantum particles behave almost outside the realms of physics.

Wormholes are theoretical tunnels that create shortcuts in space-time. A study in May from Dr Luke Butcher at Cambridge University argued that if a thin wormhole stayed open long enough, people could send messages through time using pulses of light, or photons

'The properties of quantum particles are "fuzzy" or uncertain to start with, so this gives them enough wiggle room to avoid inconsistent time travel situations,' said professor Timothy Ralph, one of the researchers on the latest study.

The results also give a better understand to how two theories in physics, on the biggest and smallest scales, are able to relate to one another.

'The question of time travel features at the interface between two of our most successful yet incompatible physical theories ' Einstein's general relativity and quantum mechanics,' said PhD student Martin Ringbauer from the University of Queensland.

'Einstein's theory describes the world at the very large scale of stars and galaxies, while quantum mechanics is an excellent description of the world at the very small scale of atoms and molecules.'

Einstein's theory suggests the possibility of travelling backwards in time by following a space-time path that returns to the starting point in space but at an earlier time - a closed timelike curve (CTC).

This possibility has puzzled physicists and philosophers alike since it was discovered by Austrian-American scientist Kurt Gödel in 1949, as it seems to cause paradoxes in the classical world.

These include the 'grandparents paradox', where a time traveller could stop their grandparents from meeting, thus preventing the time traveller's birth.

This would make it impossible for the time traveller to have set out in the first place.

But this new research suggests such interactions are indeed possible - albeit only on a quantum level for now.