# The 'Delayed Choice Quantum Eraser' Neither Erases Nor Delays

## TL;DR

The paper clarifies that quantum eraser experiments do not erase information or demonstrate retrocausality, instead highlighting misconceptions arising from improper state assumptions and comparing spatial and spin state spaces.

## Contribution

It provides a critical analysis showing that quantum eraser experiments do not erase information or imply retrocausality, challenging common interpretations.

## Key findings

- Quantum eraser experiments do not erase information.
- No evidence of retrocausality in delayed choice experiments.
- Misinterpretations stem from improper state assumptions.

## Abstract

It is demonstrated that 'quantum eraser' (QE) experiments do not erase any information. Nor do they demonstrate retrocausation or 'temporal nonlocality' in their 'delayed choice' form, beyond standard EPR correlations. It is shown that the erroneous erasure claims arise from assuming that the improper mixed state of the signal photon physically prefers either the 'which way' or 'both ways' basis, when no such preference is warranted. The latter point is illustrated through comparison of the QE spatial state space with the spin-1/2 space of particles in the EPR-spin experiment.

---
Source: https://tomesphere.com/paper/1905.03137