Chinese scientists have observed the "projection" of gravitons for the first time in the world.

It was learned from Nanjing University that the international scientific research team led by Professor Du Lingjie from the School of Physics of the university has made significant progress in the field of quantum physics and observed for the first time the "projection" of gravitons in condensed matter. Related papers were published online in the international academic journal Nature on March 28.

Du Lingjie introduced that gravitons correspond to gravitational waves. The latter has been confirmed by experiments, while gravitons have not yet been directly observed. "The graviton is the product of the combination of general relativity and quantum mechanics. If the existence of this mysterious particle can be confirmed, it may help achieve the unification of the two theories, which is of great significance to contemporary physics."

He told reporters that in recent years, there have been theoretical predictions that there may be a "fractional quantum Hall effect graviton" in condensed matter. Because its behavior laws are similar to graviton, it is vividly called the "projection" of graviton.

Five years ago, Du Lingjie's team discovered a new collective excitation phenomenon in the fractional quantum Hall effect. The theoretical physics community believes that this may be evidence for the existence of the fractional quantum Hall effect graviton, and proposed an experimental plan.

"But at that time, there was no measuring equipment at home and abroad that met the experimental requirements. Because this experiment requires extremely high equipment and seems contradictory." Liang Jiehui, co-lead author of the paper and a doctoral student at Nanjing University, told reporters that on the one hand, the experiment requires extremely low temperatures and a strong magnetic field-the temperature is only about 0.05 degrees Celsius higher than absolute zero, and the magnetic field strength must reach more than 100,000 times that of the earth's average magnetic field. Although these two conditions can be achieved by a special refrigerator, on the other hand, in order to carry out optical measurements, a light-transmitting window must be installed on the refrigerator, which can easily lead to an increase in the experimental temperature. Machine vibration can also affect the accuracy of optical measurements.

The team spent more than three years independently designing, integrating and assembling a set of experimental devices on the campus of Nanjing University. "You can understand it as a two-story 'microscope'." Du Lingjie said that after testing, many measurement parameters of the device have reached the world's leading level.

Relying on this weapon, the team successfully observed fractional quantum Hall effect graviton in gallium arsenide semiconductor quantum wells, and confirmed relevant experimental evidence from three aspects: spin, momentum, and energy.

"This is the first time that the concept of graviton has been observed in experiments since it was proposed in the 1930s." Du Lingjie said that the team will continue to study the physical world of gravitons in depth,"looking forward to this 'microscope' bringing us more new discoveries in quantum frontiers."