Bose Einstein Condensates (An Application of Ultra Cold Atoms)

Michelle Ncube
Oct 17, 2025
3 min read

Did you know, there are more than 4 states of matter? One state of matter I’ll be writing about in this blog is the Bose-Einstein Condensate and how it is formed?

This blog is an extension of The coldest places on Earth; Ultra Cold Atoms !

What are Bose-Einstein condensates (BECs) ?

A Bose-Einstein Condensate is formed when bosonic atoms are cooled to fractions above absolute zero. At these extreme temperatures, they lose their individuality and behave as if they are one single atom, all moving together with the same speed and direction.

Microscopically, the wave-functions of each bosonic atom begin to overlap and merge into a single wave-function that describes the entire system. These waves are not physical waves but mathematical descriptions of where a particle could be. The wave-function just describes the behaviour of atoms and tells us the probability of us measuring the particle at a particular position.

This idea was first theorised by Satyendra Nath Bose in 1924. He described the quantum statistics of bosons and sent one of his papers to Albert Einstein. Then, Einstein extended the theory and predicted that bosons could condense into a single quantum state which we call Bose-Einstein condensate. This is also how this state of matter got its name.

BECs were not created in the lab until 1995 by Eric Cornell, Carl Wiemann and their team of Physicists. The group trapped and cooled 100,000 rubidium-87 atoms to around 170 nano-kelvin. In the same year, Wolfgang ketterle also achieved condensation with rarefied sodium atoms.

In 2001, the three ended up winning a Nobel Prize for their achievement.

Why must we use bosonic atoms in BECs?

To understand this, knowing what bosonic atoms are is crucial.

What are bosonic atoms?

Particles can be categorised into 2 main groups based on their quantum spin (intrinsic angular momentum).These categories are called fermions and bosons.

Fermions have a half integer spin (e.g. protons & neutrons)

Bosons have an integer spin (e.g. photons, gluons & atoms like Rb-87)

Why must a BEC only have bosons?

The reason as to why these atoms can only be bosons is related to their wave-functions and how their quantum states behave when you swap them.

A wave-function is a mathematical shape which describes where a particle could be and how it behaves. The particle could be anywhere on this wave. If the wavefunction is large at a specific point, the particle is more likely to be found there.

For bosons, they have wave-function that is symmetrical.

So, if I were to swap two identical bosons (pretending that boson A is boson B vice versa), the wavefunction will not change. This means bosons can share the same quantum state

However, for fermions, this is not the case. Fermions wave-functions are not symmetrical, when swapping 2 fermions, their wavefunction changes sign. This anti-symmetry means two fermions can’t occupy the same quantum state.

This is where the Pauli-exclusion principle arises which states that no two fermions can occupy the same quantum state at the same time.

Because forming a BEC requires lots of particles joining into a single shared wave-function, fermions are not able to form BECs on their own.

However, fermions can boson up and form composite bosons which I won’t go further into, in this blog ;).

Applications of Bose - Einstein Condensate?

The creation of Bose Einstein condensates through ultra cooling techniques helps us do the following:

Atomic Lasers
Similar to an optical lasers, BECs can produce coherent beams of atoms as they share the same wave-function.This is significant as it can be used in nanotechnology and improving precision of experiments.

Quantum computing
These condensates can be used as qubits which are encoded in the different internal spins of atoms. As BECs have many atoms, the quantum information can be duplicated across the identical particles reducing the amount of qubits needed.

Precision measurement
We can use BECs to detect gravitational waves at frequencies that LIGO (Laser Interferometer Gravitational-Wave Observatory) cannot sense. BECs can also sense rotation and acceleration with extreme precision allowing for even more precise navigation systems to be generated for submarines, aircraft and even spacecraft.

Quantum simulators
We can use BECs to stimulate systems we would not be able to easily create in nature, such as Black hole event horizons, superfluids and behaviour of quark-gluon plasmas. This us to learn more about how the far away systems work.

Further reading / Interesting Topics