Quantum Computation vs. Firewalls

TL;DR

This paper argues that quantum computational limits prevent certain black hole thought experiments, suggesting a broader non-locality that could eliminate the need for firewalls without compromising unitarity.

Contribution

It demonstrates that the quantum computational complexity of these experiments is exponential in black hole entropy, challenging their feasibility and implications.

Findings

Quantum computations for these experiments are exponentially slow.

Such experiments are generally infeasible for large black holes.

Broader non-locality may resolve firewall paradox without violating unitarity.

Abstract

In this paper we discuss quantum computational restrictions on the types of thought experiments recently used by Almheiri, Marolf, Polchinski, and Sully to argue against the smoothness of black hole horizons. We argue that the quantum computations required to do these experiments take a time which is exponential in the entropy of the black hole under study, and we show that for a wide variety of black holes this prevents the experiments from being done. We interpret our results as motivating a broader type of non-locality than is usually considered in the context of black hole thought experiments, and claim that once this type of non-locality is allowed there may be no need for firewalls. Our results do not threaten the unitarity of of black hole evaporation or the ability of advanced civilizations to test it.