Researchers have discovered new multiphoton effects in quantum interference of light

An international research team from Leibniz University in Hanover and Strathclyde University in Glasgow overturned the previous hypothesis about the influence of multiphoton components in the thermal field and the interference effect of parameterized single photons. The journal Physical Review Letters published the team's research.

"We have demonstrated through experiments that the interference effect between thermal light and parametric single photons can also lead to quantum interference with the background field. For this reason, the background cannot be simply ignored and subtracted from the calculation, as has been the case so far," said Professor Michael Kues, Director of the Institute of Photonics at Leibniz University in Hanover and member of the board of directors of the Phoenix D Excellence Cluster.

The leading scientist is doctoral student Anahita Khodadad Kashi, who is engaged in research on photon quantum information processing at the Institute of Photonics. She studied how the visibility of the so-called Hong Ou Mandel effect is affected by multiphoton pollution.

"Through our experiment, we have overturned the previously valid assumption that the multiphoton component only damages visibility and can therefore be subtracted from the calculation," said Khodadad Kashi. We have discovered a new fundamental feature that has not been considered in previous calculations. Our newly developed model can predict quantum interference, and we can measure this effect in experiments.

Scientists discovered their findings while conducting experiments in the laser laboratory. When they initially followed the original calculation method, they obtained negative results. "But the result is physically impossible," said Khodadad Kashi. The team started troubleshooting the experimental setup and computational model together.

"When the experimental results deviate significantly from expectations, scientists begin to question previous hypotheses and seek new explanations," Kuss said.

They jointly developed a new thermal field quantum interference theory, which uses parameterized single photons. Lucia Caspani, a quantum researcher at Strathclyde University in Glasgow, was the first to test this method. Next, Khodadad Kashi presented her theory and experimental results at an international conference, including the Photonics West held in San Francisco. There, she discussed her model with other scientists and obtained confirmation of her results.

Through new theories and experimental verification, Kues's team has made significant contributions to a better understanding of quantum phenomena. "These findings may be important for quantum key distribution, which is necessary for future secure communication, especially how to explain quantum interference effects to generate keys," said Khodadad Kashi.

However, many questions remain unanswered, Kues said. There is little research on the multiphoton effect, so a lot of work still needs to be done.

Source: Laser Net