How Bose Einstein Condensate Was Discovered and Why It Matters
Bose Einstein condensate (BEC), a defined as a state of matter, in which separate subatomic particles or atoms, cooled to approximately absolute zero (0 K, − 459.67 °F or − 273.15 °C; K = kelvin), coalesce into an entity of single quantum mechanical. It means one that can be defined by a wave function - on a near-macroscopic scale. This matter form was predicted by Albert Einstein in 1924 based on the quantum formulations of the Indian physicist named Satyendra Nath Bose.
More about Bose Einstein Condensate
Although this had been predicted for decades, the first atomic BEC was formed only in 1995, when Carl Wieman and Eric Cornell of JILA, a research institute operated jointly by the NIST (National Institute of Standards and Technology) and the University of Colorado at Boulder, cooled rubidium atom gas to 1.7 × 10−7 K more than absolute zero. Including Wolfgang Ketterle of the MIT - Massachusetts Institute of Technology, who created a BEC with sodium atoms, these researchers have received the 2001 Nobel Prize for Physics. BEC research has expanded the quantum physics understanding and has led to the discovery of new physical effects.
Traces back to 1924, BEC theory, when Bose considered how photon groups behave. Photons belong to the two great classes of submicroscopic or elementary particles described by whether their quantum spin is an odd half-integer (1/2, 3/2, …) or non-negative integer (0, 1, 2, …). The former type, known as bosons, includes photons, whose spin is given as 1. The latter type, which is fermions, includes electrons, whose spin is given as 1/2.
As noted by Bose, the two classes behave in a different way, noticed in Fermi-Dirac and Bose-Einstein statistics. As Pauli's exclusion principle says, fermions tend to avoid each other, for which reason every electron in a group occupies a separate quantum state (which is indicated by different quantum numbers, like an electron's energy). In contrast, an unlimited count of bosons may contain similar energy states and share a single quantum state.
BECs Are Related to Two Remarkable Phenomena of Low-Temperature
This happens due to superfluidity, where each of the helium isotopes 3He and 4He produces a liquid that flows with zero friction, and superconductivity, where electrons move through a material with zero electrical resistance. The 4He atoms are bosons, and although 3He electrons and atoms are fermions, they can also undergo Bose condensation if they pair-up with the opposite spins to produce boson-like states with zero net spins. Deborah Jin, including her colleagues in 2003 at JILA have used paired fermions to create the first atomic fermionic condensate.
The research of BEC has yielded new optical and atomic physics, like the atom laser Ketterle demonstrated in the year 1996. A conventional light laser emits coherent photon beams; they are all exactly in phase and are focused on an extremely small, bright spot. In the same way, an atom laser forms a coherent beam of atoms that is focused at high intensity. Potential applications are more-accurate atomic clocks and enhanced techniques to manufacture integrated circuits and electronic chips.
BEC's most intriguing property is, it can slow downlight. In 1998, Lene Hau of Harvard University, including her colleagues, slowed light travelling through a BEC from its speed in the vacuum of 3 × 108 meters per second to a mere of 17 meters per second, or up to 38 miles per hour. From then, Hau and others have completely stored and halted a light pulse within a BEC, later releasing the light unchanged or sending it to the second BEC. These manipulations hold promise for newer light-based telecommunication types, quantum computing, and optical storage of data, though the low-temperature requirements of BECs offer practical difficulties.
Experimental Observation
In 1938, John Allen, Don Misener, and Pyotr Kapitsa discovered that helium-4 became a new kind of fluid, which, now called superfluid, at temperatures below 2.17 K (which is the lambda point). Superfluid helium has several unusual properties, including zero viscosity (which is the ability to flow with no dissipating energy) and the quantized vortices' existence. Also, it was quickly believed that the superfluidity was because of the partial Bose-Einstein condensation of the liquid.
Several properties of superfluid helium appear in the gaseous condensates, which are created by Wieman and Ketterle, Cornell. Superfluid helium-4 is considered a liquid rather than a gas. This means the interactions between the atoms are said as relatively strong; the original Bose-Einstein condensation theory should be heavily modified to describe it. However, Bose-Einstein condensation remains fundamental to the superfluid helium-4 properties. It should also be noted that a fermion, helium-3, which also enters into a superfluid phase (at a very lower temperature), can be explained by the formation of the bosonic Cooper pairs of two atoms.
FAQs on What is Bose Einstein Condensate?
1. What is the Bose-Einstein condensate (BEC)?
A Bose-Einstein condensate (BEC) is considered the fifth state of matter. It forms when a gas of special particles called bosons is cooled to temperatures very close to absolute zero (-273.15°C). At this point, the atoms lose their individual identities and start behaving as a single quantum entity, sometimes called a "superatom."
2. How is a Bose-Einstein condensate formed?
To create a BEC, scientists use a two-step process. First, they use lasers to trap and slow down atoms, which cools them significantly. Then, they use a method called evaporative cooling. In this step, the most energetic ("hottest") atoms are allowed to escape the trap, which lowers the average temperature of the remaining atoms until they are just a fraction of a degree above absolute zero and condense into the BEC state.
3. Why is this state of matter called Bose-Einstein condensate?
The name comes from the two scientists who predicted its existence. In the 1920s, Indian physicist Satyendra Nath Bose did pioneering work on the statistics of these particles (bosons). Albert Einstein then used Bose's ideas to predict that if you cool these bosons down enough, they would "condense" into this new, single quantum state.
4. Are there any real-world examples of Bose-Einstein condensates?
Bose-Einstein condensates are primarily created in highly controlled laboratory settings and do not exist naturally on Earth because they require temperatures colder than deep space. They are made from elements like rubidium, sodium, or lithium. While not a household item, their properties are used to study quantum mechanics.
5. What are some important applications of BEC?
BECs have several potential and current applications in science and technology, including:
- Precision Measurement: They can be used to build extremely sensitive detectors for gravity and rotation, leading to better navigation systems.
- Quantum Computing: Their unique quantum properties are being explored for creating qubits, the building blocks of quantum computers.
- Simulating Complex Systems: They can model the behaviour of complex quantum phenomena, like superconductivity or the conditions inside neutron stars.
6. How is a Bose-Einstein condensate different from plasma?
They are essentially opposites in terms of energy. Plasma, the fourth state of matter, is a super-heated gas where atoms are stripped of their electrons, forming an ionised gas at extremely high temperatures. In contrast, a Bose-Einstein condensate is formed at extremely low temperatures, close to absolute zero, where atoms merge into a single quantum state.
7. What makes the Bose-Einstein condensate so unique compared to solids, liquids, or gases?
Unlike solids, liquids, or gases where atoms act as individual particles, the atoms in a BEC lose their individuality. They all occupy the lowest possible energy state and behave as one single, massive particle or "superatom." This allows scientists to observe quantum mechanical effects on a macroscopic (visible) scale, which is not possible with other states of matter.
8. Why does a Bose-Einstein condensate only form at extremely low temperatures?
Temperature is a measure of the random motion of atoms. At normal temperatures, atoms have too much energy and move around too fast to show their quantum nature. By cooling them to near absolute zero, their motion is almost completely stopped. This allows their quantum properties, which are like waves, to overlap until they merge into a single, coherent matter wave, forming the condensate.
9. What happens to the individual atoms inside a Bose-Einstein condensate?
Inside a BEC, the atoms stop behaving like distinct points and their quantum wave-like nature takes over. As they get colder and closer, their individual "matter waves" spread out and overlap. At the condensation point, they merge into a single, unified matter wave. It's like many separate ripples in a pond merging to form one single, large wave. This is why the entire group of atoms can be described by a single quantum wavefunction.
