Comment on "Generating a perfect quantum optical vortex"

TL;DR

This paper critiques a previous claim that a simple lens can generate a perfect quantum optical vortex state, clarifying that quantum noise distribution cannot be altered by a lens and requires an 'effective lens' instead.

Contribution

It corrects the misconception about generating perfect quantum optical vortex states using a lens, emphasizing the need for an 'effective lens' to modify quantum noise.

Findings

A simple lens cannot modify quantum noise distribution.

Generation of perfect quantum optical vortex states requires an 'effective lens'.

Clarifies the difference between classical and quantum optical transformations.

Abstract

In a recent article, Banerji et al. introduced a novel quantum state of light, coined as the perfect quantum optical vortex state [Phys. Rev. A 94, 053838 (2016)] due to its mathematical similarity with the classical perfect vortex beam. This state is obtained by means of the Fourier transform of a Bessel-Gaussian vortex state, and the authors claim that this can be accomplished by means of a simple lens. Here, we will show that this statement is wrong since a lens cannot modify the quantum noise distribution related to the input optical quantum state and this has to be exchanged by an "effective lens".