It\'s not often that you get to be around for the birth of a new form of
matter, but when you do, the excitement is tremendous. **\[Patrick --
couldn't we insert a quote here from Ketterle suggesting how tremendous
it was? This is an excellent place for a [human reaction]{.underline}.
Is there something in that hour-long audio file -- the lecture you
pointed me to -- or from your own interview that might serve? Paraphrase
if necessary. We'll get Ketterle to approve it.\]** Since its first
creation in 1995, this fourth state of matter has sparked a flurry of
research activity and even captured the esteemed Nobel Prize in Physics.

Called a Bose-Einstein condensate (BEC), this exotic form of matter
provides a new window into the strange world of quantum mechanics, and
could help enable technologies ranging from hyper-accurate atomic clocks
to nanotechnology and quantum computing.

Everybody knows the other three states of matter: the familiar solids,
liquids, and gases. What could a *fourth* state of matter possibly be
like? It\'s difficult even to imagine. Don\'t worry \-- it\'s much, much
stranger than you think. **\[BECs are not the [4^th^]{.underline} state
of matter. Physicists already call plasmas -- totally ionized gasses --
that. How about saying instead: "What might a [new]{.underline}
unfamiliar state of matter be like? Not wet, not firm, not wispy --
something totally outside our experience with no adjectives to describe
it. Stretch your imagination to its limits -- and BECs will still be
much stranger than you think."\]**

A BEC is almost like a little piece of another world. This odd world,
where matter can be in two places at once and can behave like both
particles and waves, exists *within* the \"normal\" matter of everyday
life. It\'s the ultra-tiny world of atoms and subatomic particles, best
described by the often paradoxical and counter-intuitive physics of
quantum mechanics.

Usually, the strangeness of the subatomic realm is (gratefully) hidden
from view in everyday life. A BEC, however, is a purely
quantum-mechanical object that\'s large enough to see with the naked
eye! The atoms in a BEC *aren\'t particles* \-- they are 3-dimensional
waves that have merged to form one collective matter-wave about a
millimeter across. **\[how many bosons does it take to make a BEC? Can
you give an example of a BEC -- like one made of helium nuclei or
something? The reader needs something to grab ahold of before the story
goes much further. Maybe something like this: "A typical BEC is made of
100 helium nuclei that merge together when cooled to super-low
temperatures. The assembly is not a giant atomic nucleus, nor is it a
molecule -- or anything from a classical physics text. Some scientists
say it's a differential equation "in the flesh." Others call it a matter
wave. Whatever you call it, it's wildly different than anything we've
experienced before..."\]**

In a sense, a BEC is the mathematical wave equation from quantum
mechanics \"in the flesh.\"

\"The pictures \[of BECs can be regarded as\] photographs of wave
functions. So if you think the \[Schrödinger\] wave function is
something mysterious, now you can photograph it, now you can see it,\"
says Wolfgang Ketterle, whose NASA-funded research on BECs earned him a
piece of the 2001 Nobel Prize. Ketterle, a physicist at MIT, shared the
award with Eric Cornell of the National Institute of Standards and
Technology and Carl Wieman of the University of Colorado at Boulder.

So what\'s so strange about a matter-wave? To be clear, a matter-wave is
*not* a wave made out of matter, such as an ocean wave. That common kind
of wave travels through a liquid, but the liquid itself is made of
particles. In a matter-wave, the material itself *is* a 3-dimensional
wave made of nothing but smaller waves.

For example, if you create two BECs and then merge them, they don\'t mix
like a liquid or deform like a solid. Where the two BECs overlap, the
material forms into thin, parallel layers of matter separated by thin
layers of empty space. The matter assumes the bar-code-like shape of an
\"interference pattern\" \-- a characteristic feature of overlapping
waves. The pattern forms because the two waves add wherever their crests
coincide and cancel each other out where a crest meets a trough (called
\"constructive\" and \"destructive\" interference, respectively).

\"That means we have two atoms from two different BECs, and we have the
remarkable effect that an atom plus an atom gives no atom. It\'s
destructive interference,\" Ketterle remarks. \"Of course we didn\'t
destroy matter, it just appeared somewhere else in the pattern, so the
total number of atoms is of course conserved.\"

The interference patterns seen in real BECs in the laboratory exactly
match the predictions of the wave function, as do the other wave-like
behaviors of BECs. Quantum weirdness has officially surfaced in the
classical world.

Having a piece of the quantum world to play with in our human-scale
world of \"classical\" physics should produce a wealth of scientific
knowledge. Many avenues are being explored and have already begun to
bear fruit. Perhaps the most important of these, though, is exploring
how systems that behave classically and those that behave quantumly
interact.

The boundary between the classical and quantum descriptions of matter
isn\'t a sharp division. If you were to \"zoom in\" on an object with
some ultra-powerful lens, the appearance of quantum behaviors would
occur gradually somewhere between the scale of a **few hundred atoms and
a few dozen**. This realm of mixed physics is tricky for scientists to
deal with.

It\'s precisely in this \"twilight zone\" that many of today\'s most
important and exciting frontiers in technology lie: smaller, faster
computer chips, micro-electro-mechanical systems (MEMS), nanotechnology,
and quantum computers.

**The magenta paragraph made my eyes glaze over:**

\"As you continue to miniaturize devices, you\'re dealing more and more
with quantum mechanics, which affects the performance of the device. So
questions about when a \[system begins to exhibit quantum properties as
it gets smaller\], such as phase memory, become quite important,\"
Ketterle says. \"\[We\'re using BECs to investigate these questions.\]\"

Like Leonardo da Vinci\'s flying machine, the idea behind BECs was
around long before the technology required to realize it. The theory was
started in 1924 by Indian physicist Satyendra Nath Bose and later
expanded by Albert Einstein \-- hence the Bose-Einstein condensate\'s
somewhat obtuse name.

According to their work, a cloud of atoms chilled to ultra-low
temperatures should coalesce into a \"quantum soup\" and then into a
single large matter-wave. But cooling matter to the needed temperature
was an impossible feat in the 1920s. The theory predicted that
condensation would occur at just a fraction of a degree above absolute
zero \-- the coldest possible temperature in the Universe, at which all
thermal motion of atoms stops (roughly -273°C, or -460°F).

At normal temperatures, the effective wavelength of an atom is smaller
than the atom itself, and so it tends to behave like a particle. But
quantum mechanics shows that as atoms become colder, their effective
wavelengths become larger, and the atoms\' wave nature becomes more
prominent. Near absolute zero, in fact, the atoms\' wavelengths become
so large that neighboring atom-waves begin to overlap, forming the
\"quantum soup.\"

The final merger into one giant wave occurs as the atom-waves all settle
into the same quantum state. (For fermions, the Pauli exclusion
principle would prevent this, so BECs can only be made from bosons,
which are exempt from the exclusion principle.) The atom-waves become
completely indistinguishable from each other and effectively behave as
one large matter-wave.

\"In an ordinary gas, atoms move around randomly, they flit around in
all directions. But in a BEC, all the atoms march lock-step,\" Ketterle
explains. \"They are just one single matter-wave propagating in one
direction.\"

If this sounds a bit like the photons in a laser beam, that\'s because
it is. BECs are quite similar to lasers in many ways. In fact,
Ketterle\'s team has succeeded in producing a pulsed \"atom laser\" from
a BEC!

Unlike the laser, though, the impact of BECs on society remains to be
seen. **\[This is confusing. At first it seems you mean "Unlike the
[atomic]{.underline} laser, though, the impact of BECs on society
remains to be seen. What you really mean is "Unlike [the familiar light
of a laser beam]{.underline}, though, the impact of BECs on society
remains to be seen."\]** Judging by the rapid blossoming of the field
since BECs\' first creation, they\'re off to an auspicious start!