Krishna: We all know about classic states of matter — solid, liquid, and gas. We are also quite familiar with plasma, which is now considered a fourth state. There may also be a fifth state of matter, and research aboard the International Space Station (ISS) has made it possible to observe Bose-Einstein condensates (BECs).

Scientists have ‘observed’ the fifth state of matter in space for the first time, offering unprecedented insight that could help solve some of the quantum universe's most intractable conundrums, research showed recently (1).

Bose-Einstein condensates (BECs)—the existence of which was predicted by Albert Einstein and Indian mathematician Satyendra Nath Bose almost a century ago—are formed when atoms of certain elements are cooled to near absolute zero (0 Kelvin, minus 273.15 Celsius).

At this point, the atoms become a single entity with quantum properties, wherein each particle also functions as a wave of matter.

A Bose-Einstein condensate is a completely different state of matter. This material is dominated by quantum effects, and that makes them enormously difficult to create. On Earth, laboratories can only maintain Bose-Einstein condensates for a matter of milliseconds. However, research aboard the ISS has created a Bose-Einstein condensate that persisted for more than a second.

This exotic material only exists when atoms of certain elements are cooled to temperatures near absolute zero. At that point, clusters of atoms begin functioning as a single quantum object with both wave and particle properties. Scientists think Bose-Einstein condensates could be the key to understanding things like dark energy and the quantum nature of the universe.

Scientists create condensates by directing atoms into microscopic magnetic “traps” that coax them into a state called quantum degeneracy. Little by little, their quantum states overlap until the condensate becomes a single wave. Scientists have to release the trap to study the material. Unfortunately, even small perturbations from the outside world disrupt a Bose-Einstein condensate. That’s why we can only maintain them for a few milliseconds on Earth. Research conducted on the space station doesn’t have to contend with gravity, allowing them to isolate the condensate more effectively (2).

In zero gravity, scientists were able to create a Bose-Einstein condensate from rubidium using shallower traps than on Earth. Even after dropping the trap, the material remained intact and in its condensate form for much longer than it would have on Earth. The team was able to take detailed measurements before the Bose-Einstein condensate dissolved.

Footnotes:

1. David C. Aveline et al. Observation of Bose–Einstein condensates in an Earth-orbiting research lab, Nature (2020). DOI: 10.1038/s41586-020-2346-1
2. Scientists Create Exotic 'Fifth State of Matter' on Space Station -....

Updates:

World's fastest Bose-Einstein condensate created

Researchers have created a Bose-Einstein condensate with record speed, creating the fascinating phase of matter in about 100 femtoseconds. To get an idea of how quick that is, hundred femtoseconds compared to one second is proportionally the same as a day compared to the age of the universe. 

Bose-Einstein condensation is a quantum phenomenon where a large number of particles starts to behave as if they were one. Albert Einstein and Satyendra Nath Bose predicted this fascinating behavior in the beginning of last century. Many different systems, like gases of alkali atoms or semiconductors coupled with light, have been used for observing these condensates. None of them comes into being, however, as fast as the Finnish researchers' Bose-Einstein condensate.

Bose-Einstein condensates composed of light are similar to lasers and particularly promising for information and quantum technologies. The information transfer of the internet today relies on the high speed of light. In principle, light can also be used to provide ultrafast computing with low energy consumption, but achieving this requires pushing the limits of what we know about the interaction of light with matter.

In our everyday world, water molecules of humid air condense on the surface of a cold beer can. Similarly, in the quantum world, particles have to find a way to lose their energy in order to condense to the lowest possible energy state. This process typically takes time from thousands of a second to trillionths of a second. How was it possible to form a condensate even faster?

After carefully analyzing their measurement data, the researchers realized that the energy relaxation in their system is a highly stimulated process. This means that the effective interaction of photons, which leads into condensation, accelerates when the number of photons increases. Such a phenomenon is the key for the speed-up.

Sources: 

Aaro I. Väkeväinen et al, Sub-picosecond thermalization dynamics in condensation of strongly coupled lattice plasmons, Nature Communications (2020). DOI: 10.1038/s41467-020-16906-1

https://phys.org/news/2020-06-world-fastest-bose-einstein-condensat...

Q: How many states of matter are there?

Krishna: There are several views on this:

This list gives some: The most familiar examples of states of matter are solids, liquids, gases, and plasmas; the most common state of matter in the visible universe is plasma. Less familiar phases include: quark-gluon plasma; Bose-Einstein condensates and fermionic condensates; quantum spin Hall state; degenerate matter; strange matter; superfluids and supersolids; and possibly string-net liquids.

https://en.wikipedia.org/wiki/List_of_states_of_matter

This says a different thing: There are now as many as eight (1): the number creeps up as science advances. Schoolkids are taught about three physical states: solid, liquid and gas. A fourth is hot, charged gas (plasma), which consists of positively charged ions and free electrons.

In 1995, scientists created a new state called ‘Bose-Einstein condensate’ by cooling gas to within a few degrees of absolute zero (-273°C), at which point molecular motion almost stops and the atoms behave en masse like a single atom. Earlier this year, researchers reported another new state for certain metals, where atoms exist as both solid and liquid at the same time.

Two other states are space-related: ‘quark-gluon plasma’, which made up the Universe up to a few milliseconds after the Big Bang, and ‘degenerate matter’, a highly compressed state that’s found in stars.

Some say it is 15 or 14 (2):  hypothetical states of matter, there are more or less 14 states of matter:

1. Solid
2. Liquid
3. Gas
4. Plasma
5. Bose-Einstein Condensate
6. Excitonium
7. Degenerate Matter
8. Photonic Matter
9. Quantum (from quantum hall effect)
10. Fermionic condensate
11. Superconductors, which although often treated as solids, are qualitatively very different from solids to be classified as such
12. Superfluids
13. Supersolids
14. Quark-gluon plasma
15. Time crystals

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Depending on what you want to count, there are either FOUR states of matter, or more than seven.

Four common states of matter easily observable on Earth:

• Solid: fixed shape, fixed volume, neutral particles.
• Liquid: fluid shape, fixed volume, neutral particles.
• Gas: fluid shape, variable volume, neutral particles.
• Plasma: fluid shape, variable volume, ionized particles.

Then there are a bunch of weirder states of matter, that require special conditions to exist:

• Degenerate Matter: crushed nuclei inside dead stars.
• Superfluid: ultra-cold, frictionless, liquid helium.
• Bose-Einstein & Fermionic Condensates: ultra-cold gases made of only bosons or only fermions (but never both) with matching spins.
• Rydberg Matter: ultra-cold tiny crystals with “delocalized” electrons.
• Quark Matter: ultra-hot soup of quarks, existed right after the Big Bang, briefly observable in the Large Hadron Collider.
• several others that have been theorized but not observed.

And then there are “non-classical states”, “mesophases”, and other variants often considered special cases of the common states at the top. Examples include glass, supercritical fluid, and liquid crystal, but there are many others depending on whether you consider the differences to define new states or not.

I suppose the number depends on what people consider as states of matter.

Citations: 

1. https://www.sciencefocus.com/science/how-many-states-of-matter-are-...

2. https://www.quora.com/What-is-a-list-of-all-the-states-of-matter