Linear-optical interferometers play a key role in designing circuits for quantum information processing and quantum communications. Even though nested Mach-Zehnder interferometers appear easy to describe, there are occasions when they provide unintuitive results. This paper explains the results of a highly discussed experiment performed by Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)] using a standard approach. We provide a simple and intuitive one-state vector formalism capable of interpreting their experiment. Additionally, we cross-checked our model with a classical-physics based approach and found that both models are in complete agreement. We argue that the quantity used in the mentioned experiment is not a suitable which-path witness producing seemingly contra-intuitive results. To circumvent this issue, we establish a more reliable which-path witness and show that it yields well expected outcomes of the experiment. In quantum mechanics (QM) particles are assigned a wave function used to describe their properties [1]. This approach sometimes leads to conclusions about experimental results that seem to contradict intuitive estimations based on classical physics [2,3]. Despite this flaw, QM is currently widely accepted as a theory [1,4], that makes accurate predictions in agreement with the performed experiments. Therefore, it is considered valid regularly used for the interpretation of the results of the corresponding experiments.Recently, an experiment that contained counterintuitive features was proposed and realized by Danan et al. [5]. The authors used nested Mach-Zehnder interferometers (MZI), shown in Fig. 1, and mirrors (A, B, C, E, F) vibrating with different frequencies, in order to leave a mark on passing photons. At one selected output port of the interferometer, the photons were detected by a quad-cell detector D capable of tracing the spatial vibrations of the photon beam. After measurement, the collected signal was further processed and subjected to the Fourier transform. From the obtained frequencies of vibrations, the authors judged whether the detected photons have interacted with the mirror that was oscillating at this particular frequency.The results described in the article by Danan et al. ence inside the interferometer, the correct application of TSVF, the processing of the obtained data and its validity. Until now, no-one has managed to provide the theoretical calculations and the interpretation of the experimental results using only the standard one-state vec-

In the year 2013, Danan et al. published a paper [Phys. Rev. Lett. 111, 240402 (2013)] demonstrating a counterintuitive behavior of photons in nested Mach-Zehnder interferometers. The authors then proposed an explanation based on the two-state vector formalism. This experiment and the authors' explanation raised a vivid debate within the scientific community. In this paper, we contribute to the ongoing debate by presenting an alternative experimental implementation of the Danan et al. scheme. We show that no counterintuitive behavior is observed when performing direct spectrally-resolved detection.