thethinkingatom

What happens to all the quantum information in a black hole when it evaporates? This is the main question of the hawking paradox. First what is quantum information?

Quantum information is the information of the particles of a substance like the bonds between atoms. In quantum terms, this is stored as the entanglement states(two particles connect so that the state of one decides the state of the other, no matter the distance) and electronic configurations of the atoms(maps out how electrons fill up shells and orbitals around an atom’s nucleus). Crushing a form of matter like a metal rod till it is not visible or barely visible does not violate the laws of physics since the quantum information is still stored with the matter of the object and not completely lost.

Lets say the metal rod was tossed into space and met a black hole. Two things would be seen from two different perspectives:

Your Perspective:
If you were at a safe distance from the black hole you would see the metal rod slowly go closer to the black hole. Eventually you would see the metal get stretched and sucked up into the 2-Dimensional surface of the Event horizon of the black hole.

From the Metal Rod’s Perspective:
If you were riding along with the metal rod as it fell, your experience would be completely different.

• Passing the Boundary: The rod passes right through the 2D event horizon intact (assuming it isn’t ripped apart by tidal forces yet).
  
• Stored in the Interior: The quantum information remains safely inside the particles of the rod as it travels through the 3D interior volume of the black hole.
  
• Destination Singularity: The information rushes toward the center, eventually hitting the singularity. A singularity is the theoretical point at the center of a black hole where matter is crushed into an infinitely small space, resulting in infinite density and gravity. The singularity can be 0 dimensional in a stationary black hole and 1 dimensional in a spinning black hole.

According to quantum mechanics, cloning quantum information is strictly forbidden (the No-Cloning Theorem). Physicists resolve this by noting that no single observer can ever see both copies at the same time. The outside observer can never look inside, and the inside observer can never communicate back out. Therefore, the laws of physics are not visibly broken to anyone.

The Black Hole Problem:
When a black hole evaporates, it emits perfectly random, featureless thermal radiation known as the Hawking radiation and when it disappears there is no trace of consumed quantum information from the matter of the metal rod that can be found.

This causes a paradox because the escaping particles are completely random and carry no information about what the black hole ate in the past. Because the black hole eventually shrinks to zero and disappears, all the information about the stars, planets, and matter that originally formed the black hole seems to vanish from the universe forever.

There is a proposed solution called as the 2D Holographic principle that saves the data:

• The 2D Scan: When the 3D metal rod falls in the black hole it’s quantum information is instantly scrambled, flattened and “recorded” on the 2D surface of the event horizon.
  
• The Radiation Interaction: Because Hawking Radiation is born exactly on this same 2D event horizon, the escaping particles do not leave empty-handed. As they fly away, they interact with the 2D surface.
  
• Taking a Copy: The 2D horizon transfers the scrambled data of the metal rod into the escaping Hawking Radiation. It prints the information onto the radiation like an invisible barcode or watermark.
  
• Safe Evaporation: When the black hole finally shrinks to nothing and vanishes, the information isn’t destroyed. It has been safely carried away encoded on the massive cloud of hawking radiation.

Without the 2D Hologram, the radiation would just be blank, meaningless heat. Without the Radiation, the data on the hologram would remain stuck at the edge of the black hole forever. Together, they ensure that when the black hole finally shrinks to zero and vanishes, the information has already safely escaped back into the universe.

A depiction of the holographic effect in action with Hawking radiation

Scientist Stephen Hawking (8 January 1942 – 14 March 2018)