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arXiv:1503.07583 · Journal of Advanced Physics

The Quantum Eraser Does Not Always Erase

António Cardoso, João L. Cordovil, J. R. Croca

Published Mar 16, 2016• 3 citations
arXivHTMLPDF

Abstract

In this paper we will first look at a particular quantum eraser setup to show that this type of experiments can be understood in an intuitive manner if we are willing to take a complex nonlinear approach, without the need to invoke Niels Bohr's complementarity or quantum entanglement between two particles. We will then discuss a recent experiment of the same type that does not erase the interference pattern when which-path information is available, and argue that this result is in clear contradiction with the orthodox interpretation of quantum mechanics but perfectly understandable in the framework of nonlinear quantum physics.

DOI
10.1166/jap.2016.1263

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In this paper we will first look at a particular quantum eraser setup to show that this type of experiments can be understood in an intuitive manner if we are willing to take a complex nonlinear approach, without the need to invoke Niels Bohr's complementarity or quantum entanglement between two particles. We will then discuss a recent experiment of the same type that does not erase the interference pattern when which-path information is available, and argue that this result is in clear contradiction with the orthodox interpretation of quantum mechanics but perfectly understandable in the framework of nonlinear quantum physics.
We present various experiments demonstrating the mutual exclusivity of observing interference and which-path information, as demanded by Bohr's complementarity principle. Using photon pairs created in parametric down-conversion, no which-path measurements need to be performed on the interfering photon itself. Instead the other photon can be used to introduce distinguishability, which consequently destroys interference. However, a suitable measurement erases this distinguishability and interference can be recovered.
The delayed-choice quantum eraser represents an interesting experiment that exemplifies Bohr's principle of complementarity in a beautiful way. According to the complementarity principle, in a two-path interference experiment, the knowledge of which path was taken by the particle and the appearance of interference are mutually exclusive. Even when the which-path information is merely retained in specific quantum path-markers, without being actually read, it suffices to eliminate interference. Nevertheless, if this path information is erased in some manner, the interference re-emerges, a phenomenon referred to as the quantum eraser. An intriguing aspect of this experiment is that if the path information is erased after the particle has been detected on the screen, the interference still reappears, a phenomenon known as the delayed-choice quantum eraser. This observation has led to the interpretation that the particle can be influenced to exhibit characteristics of either a particle or a wave based on a decision made long after it has been registered on the screen. This idea has sparked considerable debate and discussions surrounding retrocausality. This controversy is reviewed here, and a detailed resolution provided. Quanta 2025; 14: 66–74.
In this paper we discuss a recent double-slit experiment where which-path information is obtained without disturbing the photons in their path to the detector, and, as a consequence, an interference pattern is observed on the far screen even if it is known which slit the photons go through. We argue that this result is in clear contradiction with a fundamental principle in orthodox quantum mechanics – Bohr’s complementarity principle – and also point out that, on the other hand, the results of this experiment are the expected ones in the framework of de Broglie’s pilot wave theory
This article develops a relational interpretation of the quantum eraser experiment, showing that interference and which‑path information are not intrinsic properties of quantum systems but context‑dependent relational structures. By analyzing the experiment without invoking retrocausality or observer‑dependent collapse, the paper demonstrates that the apparent paradox arises from mixing incompatible informational frames. Interference is recovered when relational coherence is preserved, while its disappearance corresponds to a change in the network of informational relations rather than a physical erasure. The model clarifies the conceptual foundations of the quantum eraser and provides a unified account of interference, measurement, and information flow.
Abstract The delayed-choice quantum eraser has long been a subject of controversy, and has been looked at as being incomprehensible to having retro-causal effect in time. Here the delayed-choice quantum eraser is theoretically analyzed using standard quantum mechanics. Employing a Mach–Zehnder interferometer, instead of a conventional two-slit interference, brings in surprising clarity. Some common mistakes in interpreting the experiment are pointed out. It is demonstrated that in the delayed mode there is no which-way information present after the particle is registered on the screen or the final detectors, contrary to popular belief. However, it is shown that another kind of path information is present even after the particle is registered in the final detectors. The registered particle can be used to predict the results of certain yet to be made measurements on the which-way detector. This novel correlation can be tested in a careful experiment. It is consequently argued that there is no big mystery in the experiment, and no retro-causal effect whatsoever.