[Paper Review] Comment on Afshar's expriments

Daniel Reitzner|ArXiv.org|Jan 22, 2007

Syntax, Semantics, Linguistic Variation2 references3 citations

TL;DR

This paper challenges Afshar's claim of observing both wave-like interference and particle-like which-way information in a double-slit experiment. Using numerical simulations based on the Huygens-Fresnel principle and lens phase shifts, the authors demonstrate that the interference pattern remains wave-dominated even after a lens, and which-way information cannot be extracted when both slits are open—confirming complementarity is preserved.

ABSTRACT

Results of the experiments carried out in [Shahriar S. Afshar, Proc. SPIE bf 5866 (2005) 229-244] and [Shahriar S. Afshar, AIP Cof. Proc. 810, (2006) 294-299] are reviewed and their interpretation by the authors is questioned. Arguments are supported by numerical simulations.

Motivation & Objective

• To challenge Afshar's claim that both interference and which-way information can be simultaneously observed in a double-slit setup.
• To demonstrate that the observed interference pattern in Afshar's experiment arises purely from wave behavior, not particle-like trajectories.
• To show that the lens-based image formation does not preserve which-way information when both slits are open.
• To validate the consistency of quantum complementarity in Afshar’s experimental setup through numerical simulation.
• To refute the interpretation that momentum conservation implies which-way information can be extracted from photon position on a detector.

Proposed method

• Numerical simulation of light propagation using the Huygens-Fresnel principle: $\Psi(r) \propto \int_{\sigma} \Psi_0(\sigma') \frac{e^{ikr}}{r} d\sigma'$.
• Incorporation of lens phase shift via $\delta(y) = -2k\sqrt{4f^2 + y^2}$, modifying the wavefront in the integral.
• Simulation of intensity distributions on the first interference plane for single-slit and double-slit configurations.
• Modeling of lensed image formation to predict focal spot positions and intensity patterns.
• Simulation of wire placement at interference minima to test robustness of interference patterns under obstruction.
• Comparison of results with and without wires to assess photon interception and intensity changes.

Experimental results

Research questions

• RQ1 Can which-way information be obtained when both slits are open in Afshar’s setup, as claimed by Afshar?
• RQ2 Do the lensed images in Afshar’s experiment preserve particle-like which-way information or are they purely wave-based?
• RQ3 Is the interference pattern observed after the lens consistent with wave-only behavior, or does it imply particle-like localization?
• RQ4 What happens to the intensity distribution when wires are placed at interference minima in the double-slit case?
• RQ5 Does the presence of wires cause a measurable intensity drop only in the single-slit case, indicating which-way information is detectable then?

Key findings

• When only one slit is open, the intensity distribution shows a single peak, and the lens forms a focused image corresponding to that slit.
• With both slits open, the interference pattern produces a double-peaked intensity distribution behind the lens, consistent with wave behavior.
• The double-peaked pattern after the lens is a result of wave interference and contains no which-way information.
• Placing wires at the interference minima does not affect the double-peaked pattern when both slits are open, as photon detection probability at those points is zero.
• When only one slit is open, wires at the former minima locations reduce the peak intensity by up to 10%, confirming detectable photon interception.
• The simulation results, based solely on wave mechanics, reproduce Afshar’s experimental observations without requiring particle-like which-way information.