Delayed-choice quantum erasers and the Einstein-Podolsky-Rosen paradox

TL;DR

This paper demonstrates that delayed-choice quantum erasers are formally equivalent to EPR-Bohm experiments, discusses their conceptual implications, classifies different types, and reanalyzes them within the many-worlds interpretation.

Contribution

It explicitly shows the formal equivalence between quantum erasers and EPR experiments and analyzes their conceptual issues and classifications.

Findings

Quantum erasers share the same formal structure as EPR-Bohm experiments.

The Scully-D"uhl-type eraser presents a more prominent conceptual mystery.

Quantum erasure can be understood through standard EPR correlations.

Abstract

Considering the delayed-choice quantum eraser using a Mach-Zehnder interferometer with a nonsymmetric beam splitter, we explicitly demonstrate that it shares exactly the same formal structure with the Einstein-Podolsky-Rosen-Bohm (EPR-Bohm) experiment. Therefore, the effect of quantum erasure can be understood in terms of the standard EPR correlation. Nevertheless, the quantum eraser still raises a conceptual issue beyond the standard EPR paradox, if counterfactual reasoning is taken into account. Furthermore, the quantum eraser experiments can be classified into two major categories: the entanglement quantum eraser and the Scully-Dr\"uhl-type quantum eraser. These two types are formally equivalent to each other, but conceptually the latter presents a "mystery" more prominent than the former. In the Scully-Dr\"uhl-type quantum eraser, the statement that the which-way information can be influenced by the delayed-choice measurement is not purely a consequence of counterfactual reasoning but bears some factual significance. Accordingly, it makes good sense to say that the "record" of the which-way information is "erased" if the potentiality to yield a conclusive outcome that discriminates the record is eliminated by the delayed-choice measurement. We also reconsider the quantum eraser in the many-worlds interpretation (MWI), making clear the conceptual merits and demerits of the MWI.