# Quantum terminology explained in the easiest way possible.

With some understanding of the concepts, it will be much easier for you to get the most out of this intriguing field. That is why I have the ambition to share here with you some simple explanations that will help you to understand the experiments we are working on.

-- Work in progress --

## Variance

Variance is a measure of how far the measurements are spread out from their average value.

If you have these two series of 5 measurements, which one has a higher variance?

Series #1: 10 20 40 80 100

Series #2: 44 48 50 51 57

The average value of both series is 50. But the deviation from that mean value is higher for series #1, so series #1 has a higher variance.

## Probability function

The probability function shows how likely it is to find a certain value at a certain position.

The easiest way to learn what it is, is to know how it is constructed. So this step-by-step plan shows how to obtain the probability function from a bunch of detected photons.

## Double slit experiment

The double slit experiment is the most famous experiment in quantum physics. Particles pass one-by-one through a pair of slits and are detected on a distant screen. After many particles are sent to the screen, an interference pattern appears (upper part of the figure). As if each particle is passing through both slits and interfering with itself.

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The interference pattern disappears when a device is located in front of the slits to measure through which slit the particle is going (lower part of figure).

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## Quantum

An important term that needs clarification is, of course, the word 'quantum':

Quantum is about special phenomena that are most visible at the smallest possible scale. We reach that level for example by zooming in into the brain, into the brain cells, into the molecules, into the atoms. At this level, totally different behaviour occurs, than what we would expect based on how we experience the world.