# Gravity and decoherence: the double slit experiment revisited

## TL;DR

This paper explores how gravity and related phenomena like thermal and Unruh radiation may cause decoherence, potentially explaining the quantum-to-classical transition observed in the double slit experiment.

## Contribution

It introduces two thought experiments that support gravity as a mechanism for decoherence, linking acceleration, radiation, and quantum interference suppression.

## Key findings

- Thermal radiation can suppress interference.
- Unruh radiation in accelerating frames can cause decoherence.
- Supports gravity's role in the quantum-classical transition.

## Abstract

The double slit experiment is iconic and widely used in classrooms to demonstrate the fundamental mystery of quantum physics. The puzzling feature is that the probability of an electron arriving at the detector when both slits are open is not the sum of the probabilities when the slits are open separately. The superposition principle of quantum mechanics tells us to add amplitudes rather than probabilities and this results in interference. This experiment defies our classical intuition that the probabilities of exclusive events add. In understanding the emergence of the classical world from the quantum one, there have been suggestions by Feynman, Diosi and Penrose that gravity is responsible for suppressing interference. This idea has been pursued in many different forms ever since, predominantly within Newtonian approaches to gravity. In this paper, we propose and theoretically analyse two `gedanken' or thought experiments which lend strong support to the idea that gravity is responsible for decoherence. The first makes the point that thermal radiation can suppress interference. The second shows that in an accelerating frame, Unruh radiation plays the same role. Invoking the Einstein equivalence principle to relate acceleration to gravity, we support the view that gravity is responsible for decoherence.