A black hole is impossible to escape. General relativity is very clear on this point. You are lost to the universe if you cross a black hole's event horizon. That isn't entirely true. It is true according to Einstein's theory, but general relativity is a classical model. It doesn't take into account nature's quantum aspects. We don't have a quantum theory of gravity. We have some ideas about the effects of quantum gravity, and one of the most interesting is the effects of Hawking radiation.

One way to study quantum gravity is to look at how objects behave in curved space. In quantum theory, we assume space is a flat background. General relativity doesn't apply. We ignore gravity since it's effects are so small. It works well for atoms in Earth's gravity. The event horizon of a black hole is very different from quantum mechanics.

The first to study the quantum effects of black holes was Stephen Hawking. We would know where the object is if it was bound by a black hole. There is always uncertainty to the location of quantum systems. There is a small chance that the quantum object is inside the black hole. objects can quantum tunnel past the horizon and escape. The less mass a black hole has, the more easily it can escape.

Black holes can emit faint energy. The effects connect black holes to thermodynamics is interesting. Black holes have a temperature because they emit light. The theory of black hole thermodynamics was developed by physicists, which helps us understand what happens when black holes merge.

How simulated black holes might be studied. Credit: Anthony Brady, University of Arizona

It's brilliant, but the problem is we haven't seen the radiation from the iwth the iwth the iwth the iwth the iwth the iwth the iwth the iwth the iwth the iwth the Most physicists think it happens, but we can't prove it. We aren't likely to detect Hawking radiation in the foreseeable future because of how faint it is. Scientists look at analog systems that have horizon-like properties.

An interesting effect of Hawking radiation was found in a recent study. There is a way to create a packet of light in a non- linear optical material. The material acts like a one-way gate, so the photons can only enter in one direction. There is a white hole at the other side of the packet. A black-hole/white-hole pair is what the optical system models.

The simulations were used to study what would happen when a quantum system passes through. The pair could be used to create a quantum effect. When two particles are created as a quantum pair, they are entangled, which means an interaction with one particle affects the other. We think that when particles escape a black hole, they do so as entangled pairs. The simulation black-hole/white-hole pair can be used to change the state of a system. The system can be adjusted to strengthen or weaken it.

The work supports the idea that Hawking radiation occurs in entangled pairs, but it also shows how entangled pairs can be changed, which would be very useful to other research, such as information theory and quantum computing. The next step is to perform the experiment in the lab. We could have a new way to study quantum systems if it works as predicted.

Agullo, Ivan, Anthony J. Brady, and Dimitrios Kranas are references.