Events

Black Holes are Watching You

Black holes have long been known to be destroyers of quantum coherence. In this talk, based on joint work with Gautam Satishchandran and Robert Wald, I show that black holes are even more insidious destroyers of quantum coherence than was previously known. I show that quantum superposition of a massive body, prepared outside a black hole horizon, will eventually decohere due to an unavoidable radiation of ultra-low-energy gravitons and photons that fall through the horizon. Indeed, we will see that the cosmological horizon also generates such decoherence, and that these decoherence phenomena can be understood as a consequence of the interrelationship between causality and quantum entanglement in a quantum theory of gravity. We sharpen this relationship to a theorem that, by analogy to thermodynamics, might be understood as a “second law” for decoherence: the decoherence outside a horizon is a nondecreasing function of time. This can in turn be seen to imply that a black hole decoheres its environment as if its interior were full of “optimal observers.”

Zoom

Monday, December 15, 2025 11:00 AM

Inperson
G10 and Zoom