# Bose-Einstein condensates coherence

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• Bone Rasta
In summary, a Bose-Einstein condensate is a coherent state, but it is different from a thermal source, which is not second order coherent due to particle correlations.

#### Bone Rasta

Hello forum! I'm studying classical and quantum coherence and there's some bug in particular I can't solve on my own, nor I could find anywhere.
I've read that a Bose-Einstein condensate is a coherent state but it seems to me inconsistent with the definition of coherence given by Glauber. In fact, he showed that a thermal source (which follows a B-E distribution), is not second order coherent because of the correlation among particles. Am I missing something?

Yes, you are missing something! Bose-Einstein condensates (BECs) are indeed a special type of coherent state. However, they are not the same as a thermal source, which follows a Bose-Einstein distribution. The coherence of a BEC is due to its extremely low temperature and the fact that all particles in the system occupy the same quantum state. This means that the particles in a BEC are perfectly correlated, and this is what gives rise to its second order coherence.

## What is a Bose-Einstein condensate?

A Bose-Einstein condensate (BEC) is a state of matter that occurs when a gas of bosons, such as atoms, is cooled to extremely low temperatures near absolute zero. At this temperature, the atoms lose their individual identities and merge together into a single quantum state, exhibiting wave-like behavior.

## What is coherence in relation to Bose-Einstein condensates?

Coherence refers to the property of a BEC where all the atoms in the condensate are in the same quantum state and behave as a single wave. This coherence allows for the BEC to exhibit unique quantum phenomena such as superfluidity and interference.

## How are Bose-Einstein condensates created?

Bose-Einstein condensates are created by cooling a dilute gas of bosonic atoms, typically using laser cooling techniques. As the temperature decreases, the atoms slow down and eventually reach a point where they lose their individual identities and merge into a single quantum state.

## What are some potential applications of Bose-Einstein condensates?

Bose-Einstein condensates have potential applications in quantum computing, precision measurements, and simulation of complex quantum systems. They can also be used to study fundamental physics principles and have been used in experiments to create artificial black holes and study quantum gravity.

## How are Bose-Einstein condensates different from other states of matter?

Bose-Einstein condensates are different from other states of matter because they exhibit quantum phenomena on a macroscopic scale. They are also highly coherent and behave as a single wave, rather than individual particles. Additionally, they can only exist at extremely low temperatures near absolute zero.