Scientists from the University of Toronto have presented a new amazing discovery related to quantum physics. In a series of experiments, they found that under certain conditions, atoms and photons can behave as if time were moving in the opposite direction. Despite such an unusual result, this phenomenon does not bring humanity any closer to the ability to travel to the past. The researchers’ work has not yet been peer-reviewed and has been on the arxiv.org platform since September.

During the experiments, the scientists directed light (photons) through a cloud of atoms cooled almost to absolute zero. In this case, the light was delayed as it passed through the medium — this effect is called group delay. The reason is that photons interact with atoms: some of them are absorbed by the electrons of the atoms, which move to a higher energy level. After this, the atoms return the absorbed energy by emitting photons and returning to their original state. Thus, the light comes out with a noticeable delay.

However, when the frequency of the photons approached the resonant frequency of the atoms, something unexpected happened: the group delay became negative. This meant that the photons seemed to “leave” the medium before they could have entered, which was confirmed by the phase shift between the control and probe beams. This phenomenon was observed thanks to the Kerr effect, and research has shown that the negative delay of light is not an error, but a real phenomenon. It can be explained by quantum superposition, when the atoms seem to “sense” the passage of photons and begin to excite in advance.

Lead researcher Josiah Sinclair from the University of Toronto explained that the negative time delay, although paradoxical, does have a physical basis. He noted: “If there were a quantum clock to measure the time that atoms spend in an excited state, then under certain conditions its hands could move backwards instead of forwards.”

While this discovery confirms that real miracles are possible in the quantum world, it unfortunately does not open the way to time travel. However, understanding phenomena such as negative time is important for future research in quantum physics and may influence further scientific discoveries.