> But the team's calculations showed there were differences in the gravitational field around the black hole. Specifically, information about the composition of the black hole was stored in gravitons, a hypothetical elementary particle that mediates gravitational forces in quantum gravity. "We found that quantum gravity enables us to find the difference in the gravitational field," Calmet said. "There's a memory in the gravitational field of what went into the black hole."
> But the team's calculations showed there were differences in the gravitational field around the black hole. Specifically, information about the composition of the black hole was stored in gravitons, a hypothetical elementary particle that mediates gravitational forces in quantum gravity. "We found that quantum gravity enables us to find the difference in the gravitational field," Calmet said. "There's a memory in the gravitational field of what went into the black hole."
https://www.livescience.com/black-hole-quantum-hair