Can a Dove prism change the past of a single photon?

Abstract

We reexamine the thought experiment and real experiment of Danan et al. (Phys Rev Lett 111:240402, 2013), Vaidman (Phys Rev A 89:024102, 2014), Vaidman (Phys Rev A 87:052104, 2013, by placing Dove prisms in the nested Mach-Zehnder interferometer arms. In those previous works, the criterion of whether a single photon was present, or not, was the presence of a "weak trace," indicating the presence of a nonzero weak value. This "weak trace" was tested by slightly varying the mirror angle at a given frequency, and then verifying whether this variation led to a signal at the corresponding frequency on a position-sensitive detector. We show that the presence of the Dove prisms gives identical weak values everywhere to the previous configuration because the prisms change neither the path difference, nor the mode profile in the aligned case. Nevertheless, the same slight variations of the interferometer mirrors now give a signal at the first mirror of the nested interferometer, indicating the photons entered the inner interferometer by the weak trace criterion. We give several possible interpretations of this effect.

Spectra in nested Mach–Zehnder interferometer experiments

“…The setup was subsequently realized in Ref. [3] and more recently, the experiment was redone in a slightly modified scheme [4], but confirming results of Danan, Farfunik, Bar-Ad, and Vaidman, also another group [5] conducted a similar experiment. These results were actively discussed in recent years (Ref.…”

“…The modification in Ref. [5] of the scheme of Ref. [3] was to put dove prisms in the arms of the smaller MZI.…”

Experimental observation of anomalous trajectories of single photons

“…In particular, it rules out the option of a continuous trajectory. The results have stirred a lively discussion in the literature [22][23][24][25][26][27][28][29][30][31][32][33] including criticism on the use of classical light and the sensitivity of the experiment. Unfortunately, the clever technique used for obtaining the "which path" information, could not be applied to single photons.…”

Null weak values and the past of a quantum particle

“…Indeed, several authors [12][13][14][15][16][17][18][19][20][21] have criticised such an idea, generally basing their critcism on the experimental realization [22] of Vaidman's nested MZI proposal. Some of the criticism [12,14,16,20] is essentially relevant to the details of the experiment (that employed tilting mirrors and classical electromagnetic waves).…”