Heavy atomic nuclei fuse together when they collide and fuse rather repulsing each other and flying apart. This is due to the motion of the internal particles that form the nucleus, as a result of an excited state of the nuclei. By following the models to describe the interactions that take place between two nuclei when they collide, the fusion rate can be calculated. But Australian physicists have contested the current models and say that the measurements they have taken during experiment do not match the predictions of the sophisticated models. They argue that during the collision, the internal structures of the nuclei get out of sync, making then behave in a macroscopic way, rather than at a quantum level.

The nuclear fusion involves smashing atomic nuclei into each other, to fuse them together to create heavier elements. The same reaction is responsible for the heat and light that the Sun is producing. The predominant element in a star's composition and the universe's, is hydrogen. So the Sun is actually 'burning' hydrogen, by defeating the electrostatic forces and merging hydrogen nuclei to create a helium nuclei and energy.

The electrostatic forces surrounding the nuclei generated by the protons is strong over relatively long distances, but the nuclear force is stronger on short distances. The "Coulomb barrier" or electrostatic barrier of repulsion can be overcome if the nuclei approach one another at fast enough speeds. Nuclei with low speeds have very little chance of fusing and simply bound off, but occasionally they can "tunnel" through the electrostatic barrier surely through a quantum-mechanic process. Improvements in the measurements of the "sub-barrier" fusion showed that the chance of two nuclei fusing once they passed the Coulomb barrier is 10 to 100 times higher than previously thought.

This improved fusion process could probably be explained through the excitation of the nucleus to higher energy states, which are mostly neglected in the simplest theories. Nuclei starting with the lowest quantum energy could evolve into an excited state, resulting in a lower energy barrier that improves the chance of fusion.

However the experiment has been extended to measure 100 million fold decrease in the fusion rate, by lowering the energy of the approaching nuclei, below the energy necessary to penetrate it. By smashing oxygen-16 into lead-204 and lead-208, they have found that the parameters which describe data above the barrier do not match the results, by using lower energies. Similar results have been experienced in the past, with lighter nickel nuclei.

The team conducting the experiment suggested that this effect could be explained by a loss of coherence of quantum phase between fusion pathways involving different energy states of the nuclei. The same effect is experienced in the experiments involving light interference. Light hitting two screen slits interfere with each other on the other side of the screen. The light captured on a distant screen appears in lines of brighter or dimmer spots, depending on the phases of light from the slits, but when a detector identifies which slit each photon of light goes through, the photon loses its phase coherence and behaves like a particle, rather than a wave.

The team hopes that the data might provide a way to solve the problem of loss of coherence by providing new insights because the interactions that lead to coherence loss are entirely within the nuclei, rather than the less controlled world outside it.