This document contains comments about the article Squeezed states of light in Wikipedia
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In the last paragraph I explain my own opinion.

### Introduction

The article starts with the following sentence.
In quantum physics, light is in a squeezed state if its electric field strength Eta for some phases Theta has a quantum uncertainty smaller than that of a coherent state.
Sentence is not clear as an introduction.
The term squeezing thus refers to a reduced quantum uncertainty.
Sentence is not clear as an introduction.
Next sentence is the same.

### 1 Quantum physical background

An oscillating physical quantity cannot have precisely defined values at all phases of the oscillation.
Any process which involves oscillations has an accuracy problem. This involves both a pendulum clock and the revolving electrons in an atom
This is true for the electric and magnetic fields of an electromagnetic wave, as well as for any other wave or oscillation.
Okay.
This fact can be observed in experiments and is correctly described by quantum theory.
Which fact can be observed?
Electro magnectic field can correctly be described by means of mathematics. The problem is to measure these fields at a certain instant.
For a displaced coherent state, the expectation (mean) value of the electric field clearly shows an oscillation, with an uncertainty independent of the phase (a).
That is what Figure 1a shows. The question is how exactly is the experiment performed that leads to this conclusion.. That same objection is valid for all the 5 examples in Figure 1.
Also the phase- (b) and amplitude-squeezed states (c) show an oscillation of the mean electric field, but here the uncertainty depends on phase and is squeezed for some phases.
Unfortunate the concept squeezed is not properly defined.

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Created: 2 March 2019

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