Knowing "where the photons have been"

Abstract

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.

4 pages, 1 figure

References in corpus (5)

• Experimental Eavesdropping Based on Optimal Quantum Cloning
• Interpreting a nested Mach-Zehnder interferometer with classical optics
• The EPR paradox, Bell's inequality, and the question of locality
• Experimental linear-optical implementation of a multifunctional optimal qubit cloner
• Efficient Amplification of Photonic Qubits by Optimal Quantum Cloning

Cited by in corpus (17)

• Past of a quantum particle: Common sense prevails
• Can a Dove prism change the past of a single photon?
• Null weak values and the past of a quantum particle
• Comment on "Past of a quantum particle revisited"
• Experimental observation of anomalous trajectories of single photons
• Comment on "One-state vector formalism for the evolution of a quantum state through nested Mach-Zehnder interferometers"
• Paradox of Photons Disconnected Trajectories Being Located by Means of "Weak Measurements" in the Nested Mach-Zehnder Interferometer
• When photons are lying about where they have been
• A Comment on "Paradox of photons disconnected trajectories being located by means of 'weak measurements' in the nested Mach-Zehnder interferometer"
• Measuring evolution of a photon in an interferometer with spectrally-resolved modes
• Spectra in nested Mach-Zehnder interferometer experiments
• A Scheme for Performing Strong and Weak Sequential Measurements of Non-commuting Observables
• Apparent quantum paradoxes as simple interference: Quantum violation of the pigeonhole principle and exchange of properties between quantum particles
• Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements
• Weak values from path integrals
• Quantum weak values and the 'which way?' question
• Interplay between strong and weak measurement: Comparison of three experimental approaches to weak value estimation