The Quantum Eraser from a Weak Values Perspective

TL;DR

This paper analyzes the quantum eraser experiment using weak value theory, clarifying the physical meaning of the results and discrediting retrocausal claims, while providing a framework for understanding interference and erasure.

Contribution

It introduces a weak value perspective to interpret the quantum eraser, clarifying the nature of interference and erasure without implying retrocausality.

Findings

Interference fringes are shown to be anomalous weak values.

Post-selection choices determine the weak values and the appearance of fringes.

Claims of retrocausal influence are discredited.

Abstract

The quantum eraser variant of the double-slit experiment, and its 'delayed choice' sub-variant, are considered from the perspective of weak value and weak measurement theory (which is briefly reintroduced here). The interference fringes that appear when measuring certain spin states, which can then be 'erased' when measuring other spin states, are shown to be anomalous weak values that depend on particular post-selection choices. By framing the choice of spin measurement as a weak value of a certain weak measurement, it is then made clear what physical claims can and cannot be made about what occurs in the quantum eraser experiment. Specifically, claims about the choice of spin-state `retrocausally' influencing the choice of slit(s) for the particles to travel through are discredited, and a simple framework is presented for understanding how the fringes arise and why they can be 'erased'.