What Is A Bose-Einstein Condensate?

Everywhere we look around ourselves, we see matter. The device you’re reading this article on, the air we breathe, along with all life on Earth is made up of matter. We can safely say that matter is everything composed of atoms. The reason we see matter taking so many different forms is because it exists in many different states. Generally, matter exists in a certain amount of states at classical conditions, but when subjected to extreme conditions, matter is found to behave in different states altogether.

One such state of matter, found at extremely critical conditions, was discovered by two legendary scientists, Satyendra Nath Bose and Albert Einstein. This state of matter was therefore given the name Bose-Einstein Condensate. First, however, to understand Bose-Einstein Condensate, we must look at the classical states of matter, refreshing how how atoms behave in them and how matter flows from one state to another.

 The Change of States of Matter

Matter has many states in which it can exist. The state of matter depends on the interaction of atoms between one another, as well as the energy levels of every atom as a whole. Matter can change from one state to another when subjected to different temperatures and pressures. Under classical physical conditions, matter can exist in four states:

  1. Solid
  2. Liquid
  3. Gas
  4. Plasma
Education Chart of Biology for Change of State for Water Diagram. Vector illustration - Vector(Vecton)S

The above depicts the classical example for change of state of matter, i.e., water (Photo Credit : Vecton/Shutterstock)

The best example for depicting changes in states of matter is water. Below 0°C, water exists in its solid state—ice. Upon heating ice above 0°C at standard pressure, it gets converted into liquid water. Upon heating liquid water above 100°C at standard pressure, we obtain steam, which is the gaseous form of water. Steam, when it undergoes the process of ionization, which adds or removes an electron to create ions, generates the plasma state of water.

The energy of atoms is the governing body to determine in which state of matter a substance is found. When we impart heat to atoms, we basically give them energy. That energy is absorbed by the atoms as they begin convert this energy into motion. This is essentially what we see during such change of states of matter. Atoms in solids have very little energy and vibrate with low amplitudes, which is why solids stay in one place. When we heat solids, we impart them with energy. The atoms then begin vibrating with more energy and higher amplitudes. This is when we obtain liquids and gases, both of which have a tendency to flow, rather than remain stagnant.

However, when we talk about Bose-Einstein Condensate, we are not talking about standard terms of physical conditions. Bose-Einstein Condensates are generally made in temperatures that are millions of times colder than space itself. Thus, to get a better understanding of the Bose-Einstein Condensate, we must go into the quantum physics of an atom.

A Dive into the Quantum Realm

Quantum Physics is the branch of physics dealing with subatomic particles and all matter and energy at the smallest scales. Quantum Physics also describes the laws governing an atom.

In 1924, Louis-Victor de Broglie claimed that all matter had a wave-like nature. This actually laid the basis for Quantum Physics. What this meant was that all matter could exist like both a particle and a wave at the same time! The reason why we don’t see this wave particle duality very often is because the mass of all objects around us has millions of millions of million more mass than the subatomic particles quantum physics deals with. In short, the objects around us have so much mass that their wave nature is almost invisible, but in small objects like electrons, we see this phenomenon more plainly.

de Broglie Matter Waves

The above shows de Broglie matter waves. The above particle is oscillating as a wave as well as moving as a particle (Photo credit: Maschen/wikimedia commons)

Quantum physics also states that each atom has its own identity. Each atom has its own unique wavelength (since it behaves like a wave) and has its own individuality as a particle. We’re able to distinguish one atom from another due to certain qualities, similar to how we can distinguish between two human beings. We must keep these laws in mind when talking about Bose-Einstein Condensate.

Wavelet

The above shows wave-particle duality. The above quantum particle is also seen as a wave-packet. (Photo credit: Thierry Dugnolle/wikimedia commons)

Turning the Microscope on the Bose-Einstein Condensate

Most of us know that there is no temperature lower than Absolute Zero, which is -273 °C or 0 K. Absolute Zero is that temperature at which atoms have no energy and cease motion entirely. So, what happens when you cool a gas with low density to temperatures only a fraction above Absolute Zero? Well, the answer to this question is… the Bose-Einstein Condensate!

It was found that upon cooling matter at temperatures just a whisker above 0 K, the material enters another state of matter, suitably named Bose-Einstein Condensate. We already know that when atoms are cooled to lower temperatures, they have lower energy levels. Thus, in the Bose-Einstein Condensate state, atoms have near-zero energy levels.

Remember the wave-particle duality of atoms covered in Quantum Physics? In a Bose-Einstein Condensate, all the atoms of a substance begin to exhibit a similar wavelength. These wavelengths then begin to overlap. At this point, the atoms undergo an identity crisis. Instead of having multiple different atoms exhibiting different wavelengths, we observe a single atom exhibiting a single wavelength. One atom cannot distinguish itself from another, so we consider the aforementioned single atom to be a “super atom”.

Quantum Physics Bose Einstein condensate

The above shows a velocity distribution of rubidium atoms. The above picture shows a velocity-distribution graph: The leftmost – atoms just before condensate is formed; Middle – a super atom just after condensate is formed; Rightmost – a pure sample of the condensate (Photo credit: National Institute of Standards and Technology / Wikimedia commons)

Conclusion

To put this very simply, the Bose-Einstein Condensate (BEC) is that state of matter where all the atoms of a particle begin to act as a single atom called a Super Atom. Unlike all the other states of matter, in the BEC, all the atoms vibrate in unison, that is, they all vibrate with the same wavelength with the same time period. This phenomenon could allow the BEC to revolutionize computation, making the realization of quantum computing possible. This concept is immensely tough to grasp and there is still a great deal of research going on related to it, but the BEC could open new and incredible doors of achievement in the world of physics.

References:

  1. Harvard University
  2. Oxford University
  3. Joint Quantum Institute
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About the Author:

Paarth is an undergraduate student pursuing a Bachelor of Technology degree in Computer Engineering. Apart from being heavily invested in cyberspace and sports, he is also passionate about the universe, history and traveling. He is an avid gamer but would prefer playing cricket, football or hockey any day. Given the choice, he would like to be a cyber security analyst, stargaze and manage a football team all at the same time.

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