Bose-Einstein condensate
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What is a Bose-Einstein condensate?
A Bose-Einstein condensate (BEC) is a state of matter formed when separate atoms or subatomic particles are cooled to near absolute zero (0 K, −273.15 °C). At this point, the atoms coalesce into a single quantum mechanical entity that can be described by a wave function on a near-macroscopic scale.
Predicted by Albert Einstein in 1924, the first atomic BEC was made in 1995 by Eric Cornell and Carl Wieman, who cooled a gas of rubidium atoms to 1.7 × 10−7 K above absolute zero. In 2001, Cornell and Wieman, along with Wolfgang Ketterle, who created a BEC with sodium atoms, received the Nobel Prize for Physics for their work.
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How is a Bose-Einstein condensate different from solids, liquids, and gases?
A Bose-Einstein condensate (BEC) is a state of matter formed when separate atoms or subatomic particles are cooled to near absolute zero (0 K, −273.15 °C). At this extreme temperature, the atoms coalesce into a single quantum mechanical entity that can be described by a wave function on a near-macroscopic scale.
Unlike solids, liquids, and gases, BECs exhibit unique quantum properties. In BECs, a large fraction of the bosons occupy the lowest quantum state, leading to macroscopic quantum phenomena. This is different from ordinary solids, liquids, and gases, where the individual particles behave independently.
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Who discovered the Bose-Einstein condensate and when was it made?
The Bose-Einstein condensate (BEC) is a state of matter predicted in 1924 by Albert Einstein based on the quantum formulations of Indian physicist Satyendra Nath Bose.
The first atomic BEC was not created until 1995, when Eric Cornell and Carl Wieman of JILA cooled a gas of rubidium atoms to 1.7 × 10−7 K above absolute zero. Wolfgang Ketterle of MIT also created a BEC with sodium atoms. Cornell, Wieman, and Ketterle received the 2001 Nobel Prize for Physics for their work with the BEC.
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How is a Bose-Einstein condensate created in a laboratory?
To create a Bose-Einstein condensate (BEC) in a lab, atoms are cooled to near absolute zero (0 K, −273.15 °C). At this extremely low temperature, separate atoms coalesce into a single quantum mechanical entity that can be described by a wave function on a near-macroscopic scale.
The process typically involves:
* Laser Cooling and Trapping: Using the radiation pressure of a laser beam to cool and localize atoms by slowing them down.
* Magnetic Confinement: Employing magnetic fields to hold the atoms in place without a material container.In 1995, the first atomic BEC was produced by cooling a gas of rubidium atoms to 1.7 × 10−7 K above absolute zero. These methods led to merging individual atoms into a "superatom" displaying distinct quantum properties.
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What makes the atoms in a Bose-Einstein condensate behave differently from atoms in other states of matter?
In a Bose-Einstein condensate (BEC), atoms behave differently than in other states of matter because they coalesce into a single quantum mechanical entity on a near-macroscopic scale.
BECs occur when separate atoms or subatomic particles are cooled to near absolute zero (0 K, −273.15 °C, or −459.67 °F). At this point, the atoms can all be treated as if they exist in the same quantum state and are part of a single large atom. Unlike fermions, which avoid each other, an unlimited number of bosons can share the same energy state. Albert Einstein showed that at extremely low temperatures "bosonic atoms" with even spins would coalesce into a shared quantum state at the lowest available energy.
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How do scientists use or study Bose-Einstein condensates in research today?
Bose-Einstein condensates (BECs) are formed when separate atoms or subatomic particles are cooled to near absolute zero, causing them to coalesce into a single quantum mechanical entity.
Scientists use BECs to expand the understanding of quantum physics and discover new physical effects. BEC research has yielded advances in atomic and optical physics, such as the atom laser. Potential applications of this technology include more-accurate atomic clocks and enhanced techniques to make electronic chips or integrated circuits.
One intriguing property of BECs is their ability to slow down light. Researchers have even halted and stored a light pulse within a BEC, which holds promise for new types of light-based telecommunications, optical data storage, and quantum computing.
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Bose-Einstein condensate (BEC), a state of matter in which separate atoms or subatomic particles, cooled to near absolute zero (0 K, − 273.15 °C, or − 459.67 °F; K = kelvin), coalesce into a single quantum mechanical entity—that is, one that can be described by a wave function—on a near-macroscopic scale. This form of matter was predicted in 1924 by Albert Einstein on the basis of the quantum formulations of the Indian physicist Satyendra Nath Bose.
Although it had been predicted for decades, the first atomic BEC was made only in 1995, when Eric Cornell and Carl Wieman of JILA, a research institution jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, cooled a gas of rubidium atoms to 1.7 × 10−7 K above absolute zero. Along with Wolfgang Ketterle of the Massachusetts Institute of Technology (MIT), who created a BEC with sodium atoms, these researchers received the 2001 Nobel Prize for Physics. Research on BECs has expanded the understanding of quantum physics and has led to the discovery of new physical effects.
BEC theory traces back to 1924, when Bose considered how groups of photons behave. Photons belong to one of the two great classes of elementary or submicroscopic particles defined by whether their quantum spin is a nonnegative integer (0, 1, 2, …) or an odd half integer (1/2, 3/2, …). The former type, called bosons, includes photons, whose spin is 1. The latter type, called fermions, includes electrons, whose spin is 1/2.
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As Bose noted, the two classes behave differently (see Bose-Einstein and Fermi-Dirac statistics). According to the Pauli exclusion principle, fermions tend to avoid each other, for which reason each electron in a group occupies a separate quantum state (indicated by different quantum numbers, such as the electron’s energy). In contrast, an unlimited number of bosons can have the same energy state and share a single quantum state.
Einstein soon extended Bose’s work to show that at extremely low temperatures “bosonic atoms” with even spins would coalesce into a shared quantum state at the lowest available energy. The requisite methods to produce temperatures low enough to test Einstein’s prediction did not become attainable, however, until the 1990s. One of the breakthroughs depended on the novel technique of laser cooling and trapping, in which the radiation pressure of a laser beam cools and localizes atoms by slowing them down. (For this work, French physicist Claude Cohen-Tannoudji and American physicists Steven Chu and William D. Phillips shared the 1997 Nobel Prize for Physics.) The second breakthrough depended on improvements in magnetic confinement in order to hold the atoms in place without a material container. Using these techniques, Cornell and Wieman succeeded in merging about 2,000 individual atoms into a “superatom,” a condensate large enough to observe with a microscope, that displayed distinct quantum properties. As Wieman described the achievement, “We brought it to an almost human scale. We can poke it and prod it and look at this stuff in a way no one has been able to before.”
BECs are related to two remarkable low-temperature phenomena: superfluidity, in which each of the helium isotopes 3He and 4He forms a liquid that flows with zero friction; and superconductivity, in which electrons move through a material with zero electrical resistance. 4He atoms are bosons, and although 3He atoms and electrons are fermions, they can also undergo Bose condensation if they pair up with opposite spins to form bosonlike states with zero net spin. In 2003 Deborah Jin and her colleagues at JILA used paired fermions to create the first atomic fermionic condensate.
BEC research has yielded new atomic and optical physics, such as the atom laser Ketterle demonstrated in 1996. A conventional light laser emits a beam of coherent photons; they are all exactly in phase and can be focused to an extremely small, bright spot. Similarly, an atom laser produces a coherent beam of atoms that can be focused at high intensity. Potential applications include more-accurate atomic clocks and enhanced techniques to make electronic chips, or integrated circuits.
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The most intriguing property of BECs is that they can slow down light. In 1998 Lene Hau of Harvard University and her colleagues slowed light traveling through a BEC from its speed in vacuum of 3 × 108 metres per second to a mere 17 metres per second, or about 38 miles per hour. Since then, Hau and others have completely halted and stored a light pulse within a BEC, later releasing the light unchanged or sending it to a second BEC. These manipulations hold promise for new types of light-based telecommunications, optical storage of data, and quantum computing, though the low-temperature requirements of BECs offer practical difficulties.