The phenomenon of sonoluminescence has fascinated scientists for decades. It's the name for what happens when a bubble in liquid implodes after being excited with sound and releases light consistent with the energy of the surface of the Sun. The exact mechanisms behind this process are uncertain but new research has found evidence that the process is quantum in nature.

Sonoluminescence isn't relegated to just the realm of laboratories, the peculiar mantis shrimp is also capable of creating it with its claws. According to a new preprint paper, yet to be peer-reviewed, the photons – particles of light – emitted by this single bubble implosion have the right signature to be consistent with a quantum process.

“We have three kinds of lights in the world. Either they are laser, and you have to spend a lot of time and energy to create a laser, or they are thermal, which is the light that usually we get from the Sun or from a tungsten lamp or a hydrogen lamp, et cetera, or they are quantum,” senior author Ebrahim Karimi at the University of Ottawa, Canada told IFLScience.

The team investigated the single bubble sonoluminescence with three different setups that allowed them to figure out that the photons are correlated and their emission, once analyzed, looks nothing like what one would get from a laser source or a more traditional thermal emission.

“We observed that photons are coming in a specific statistic. And this specific statistic is known as sub-Poissonian,” Karimi explained to IFLScience. “And this is a confirmation that this phenomenon is quantum in nature, purely quantum, and has no classical analog.”

Lasers and thermal sources of light are described using a classical electromagnetic understanding of light. But sources that have a sub-Poissonian distribution have no equivalent in the classical world.

This discovery is pretty exciting for a few reasons. It provides insight into the mysteries still shrouding sonoluminescence. But, as the team plans on investigating, it might also provide a cheaper and easier way to create a quantum light source.

Karimi believes that the photons produced are entangled pairs – which means that each couple formed is a single quantum state no matter how far apart they might get. Their next investigation might reveal if this is the case. And if that is true and the sonoluminescence can be made smaller so that it produces just a handful of photons, all entangled, this could be very useful in lots of other scientific investigations that require expensive lasers and light equipment.