Is it time to start investing in Bose-Einstein condensates? They’re not dew drops, of course. Anything with ‘Einstein’ in it has got to be physics. So what kind of condensate is this, and what makes it (potentially) useful?

The concept of Bose-Einstein condensates, often abbreviated BEC, was theorized by Satyendra Nath Bose and Albert Einstein in 1924-1925, but not produced in a laboratory until 1995. Carl Wieman, Eric Cornell, and Wolfgang Ketterle received the 2001 Nobel Prize in Physics for the work. Still, Bose-Einstein condensates are not well known outside the physics community (understatement). To use the colloquial, they’re pretty special.

To begin with, only certain atoms qualify to become a Bose-Einstein condensate. They must be bosons, identical particles with an integer spin (the rotation of each particle is a whole number). Photons qualify as do Helium-4 atoms (sort of) and Rubidium atoms. The key is that boson particles can exist together at the same quantum state, which makes it possible to concentrate them. The first BEC particles were made by cooling a gas of rubidium atoms to 170 nanokelvin. The Kelvin scale of temperature starts at absolute zero (0 degrees Kelvin or -273 degrees Celsius). That is so cold even atoms have no motion, no energy. 170 nanokelvin is just a smidgeon above absolute zero (1.7 x 10-7 to be exact). At that extreme temperature the bosons fall (“condense”) into the lowest quantum state, and as Einstein predicted, a new kind of matter is created – a single ‘super-particle’.

A super-photon is one of these new kinds of matter. It was not considered possible to create them. Although Bose and Einstein stated their theory in terms of photons, physicists were unable to make them in the laboratory because as photons cool toward absolute zero they disappear. They disappear literally and figuratively: As they lose temperature photons change their light frequency until finally they leave the visible spectrum and become infrared light (invisible to the human eye). As photons cool through the infrared spectrum, there are fewer and fewer of them – until there are no more. This disappearing act appears to make a Bose-Einstein condensate of photons seemingly impossible.

Physicists, however, can be clever. Four physicists at Bonn University (Germany), Jan Klaers, Julian Schmitt, Dr. Frank Vewinger, and Professor Dr. Martin Weitz published their successful technique in the November 2010 issue of Science [Bose–Einstein condensation of photons in an optical microcavity]. They created a specialized cold-chamber (actually a miniscule cavity) with two highly reflective mirrors and bounced light (photons) between them. Between the mirrors was a layer of dissolved pigment molecules in a fluid. As the photons passed through the layer, some of them temporarily became engaged with the pigment and cooled to the pigment’s temperature – room temperature. As the temperature dropped, a laser beam was added to excite the pigment molecules so that even more photons were cooled. Eventually the point of condensation was reached, and the photons ‘clumped together’ (condensed) into a super-photon particle.

Remember, this condensate is made of photons – light – so the end product is a new kind of light. In fact, when it was first created, the scientists knew it was there because in the center of the chamber there was a yellow laser-like light.

A ‘photonic Bose-Einstein condensate’ has the characteristics of a laser light source, so at least theoretically it could be used for laser-type applications. Here is where the commercial interest begins. Unlike ordinary lasers, which operate in the visible light spectrum, a BEC super-photon operates at X-ray frequencies. The X-ray frequency (wave length) is much shorter and more powerful than visible light. This could be extremely valuable in the process of etching silicon chips with complex and very, very small circuitry. (Current chips are made with standard lasers.)

The technique could also be used to create solar cells that can focus and capture sunlight even on a cloudy day.

No surprise, however, that these practical applications are potential only. Harnessing photons to make a BEC is considered relatively simple by this method, but that’s in a laboratory. At a commercial scale and in a variety of environments – well let’s say that success is not a given. However, now that a BEC super-photon is no longer theory, there will be many who will push very hard to find practical applications – any of them could revolutionize the making of electronics, or change the game in solar energy.

“On a scale of nanometers, we create an inexorable and destructive pull similar to what black holes exert on matter at cosmic scales,” says Lene Vestergaard Hau, Mallinckrodt Professor of Physics and of Applied Physics at Harvard. “As importantly for scientists, this is the first merging of cold-atom and nanoscale science, and it opens the door to a new generation of cold atom experiments and nanoscale devices.”

“From the atom’s point of view, the nanotube is infinitely long and thin, creating a singular effect on the atom,” Hau says.

[Source: EurekAlert]

The experiments that produced this effect have a kind of drama to them.

It starts in a tiny cryochamber (super cold) where atoms of rubidium have been chilled by laser manipulation to a fraction of a degree (Kelvin) above absolute zero. Then like a cloud one millimeter in length the atoms are propelled toward a single nanotube, suspended in the chamber, similarly cooled but charged with hundreds of volts. The distance is short, two centimeters; even so something dramatic happens to the atoms. Most of the atoms go zipping by the nanotube, but some that come within less than a micron are pulled toward it. They spiral inward gaining fantastic speed – from 5 meters per second to 1,200 meters per second (2,700 miles per hour). Because they are going so fast, the atoms heat from near absolute zero to thousands of degrees Kelvin in less than a microsecond. Coming closer to the nanotube, the atoms start to go really fast and separate into an electron and an ion rotating in parallel. Each orbit takes only a few trillionths of a second. Suddenly the electron is sucked into the nanotube (via quantum tunneling) and the ion goes rocketing away. It’s so repelled by the strong charge of the nanotube that it is travelling at 26 kilometers per second (59,000 miles per hour). Then it’s over, ions dispersed and atoms disintegrated.

It’s all over in a few microseconds. In this super cold, super controlled environment nearly everything gets monitored and measured. The scientists have a ton of data to sift. Some of that has already been done, but it’s clear that in this case they’re still trying to find appropriate points of reference. Black hole isn’t really such a touchpoint, although the image of atoms sucked into a tube sort of fits. What really is going on – why the nanotube has such ‘powers’ – is an open question, as is the question of what this effect might do or be used for.

By ‘higher temperatures’ this does not mean room temperature, but it does mean up to 50 degrees Kelvin, which is substantially warmer than 4 degrees Kelvin. They accomplished this by doing what physicists call “squeezing.” In quantum physics, the more accurately positions (of atomic particles) are measured, the less can be determined about their momentum. Similarly, measuring time decreases the measurement of energy, or phase amplitude. (This is remindful of the old bromide: You want quick, easy, and cheap? Pick any two.) The effect is called the Heisenberg uncertainty principle, which places limits on how well pairs of complementary properties can be observed.

Physicists have learned how to juggle the measurements to optimize one measurement or another. This is “squeezing.” What the Spanish team wanted to know was could squeezing be applied to a quantum situation where everything was changing (that is, in disequilibrium – whereas most such research is done in an equilibrium state). To test this, they used a pair of driven (by magnetic fields) quantum oscillators that are entangled in a ‘hot’ environment. Because they could control temperature and the driving force of the oscillators, they could constantly squeeze the system, and the entanglement was retained at higher temperatures. How high could this go?

Galve and co say this depends on the coupling between the oscillators. But they calculate that entanglement between a pair of calcium ions in an rf trap–a standard set up in many labs–and show how it could be sustained at 50K. That’s significantly better than the sub-4K systems that experimenters have to manage with today. “We believe this to be a huge experimental step,” they say.

What about room temperature experiments? That would require a very strong coupling and may cause other problems. The squeezing causes the quantum states to become more delocalised, in other words they become smeared out in space. That could be a problem if the ions end up largely outside the trap in which they are supposed to be confined.

[Source: Technology Review]

This new approach – exploring quantum entanglement in non-equilibrium systems – is not only an important step for quantum physics, but apparently it’s also a step in the direction already taken by Nature.

Scientists have long known how to control the internal states of molecules, such as their rotational and vibrational energy levels. In addition, the field of quantum chemistry has existed for decades to study the effects of the quantum behavior of electrons and nuclei—constituents of molecules. But until now scientists have been unable to observe direct consequences of quantum mechanical motions of whole molecules on the chemical reaction process. Creating simple molecules and chilling them almost to a standstill makes this possible by presenting a simpler and more placid environment that can reveal subtle, previously unobserved chemical phenomena.

[Source: EurekAlert]

The new research started with the premise that in extreme cold – a few hundred billionths of a Kelvin (nanokelvins) above absolute zero (minus 273 degrees Celsius or minus 459 degrees Fahrenheit – no chemical reactions should occur.

The physicists at JILA (formerly the Joint Institute for Laboratory Astrophysics, now just JILA, a joint venture of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, USA) cooled a gas of potassium and rubidium molecules to this temperature and subjected them to manipulation with electric fields. Then they observed the unexpected – heat – a few billionths of a degree to be sure, but measurable proof that chemical reactions were taking place and, in fact, taking place very quickly.

Taking the experiments further, the researchers worked with the gas as a 50/50 mix of molecules with two different ‘spins’ (that’s spin in the quantum sense, the angular momentum) and found that this increased the speed of reaction up to a hundred-fold. This is indicative that manipulating quantum properties (electronic, vibrational and rotational states) changes the chemical reaction.

How this works is still very much up for more research. These are ‘toe in the water’ experiments that only hint at what’s happening. Outside of masses of equations for the highly trained few, an intuition for molecular quantum chemistry are difficult to explain. I’ll try.

Here’s a crude analogy to work with: Consider two magnets, tiny bars with polar ends. We know that putting to unlike poles together and the bars attract each other. They repel each other when two like poles are put together. Simple magnetic properties. Now visualize these bars having unequal magnetic energy, one bar is more strongly magnetized than the other; that they are rotating very fast; spinning (with different total angles of momentum) so that the orientation of the poles continually changes, and that each bar is vibrating at different rates. What happens to the magnetic properties? How would these two bars react to each other? The quantum mechanics of molecules isn’t the same as this kind of magnetism, but perhaps this helps visualize how differently the magnets might behave when the extra conditions are added. That complex behavior is analogous to what it’s like for molecules undergoing quantum chemistry, and why, when scientists get their first glimpses of such behavior, they realize that underlying all that we think we know about chemistry, is another, more subtle but nevertheless decisive set of behaviors that governs how molecules react to each other.

I’m searching for a metaphor – a door opening, curtain rising, fog lifting – not really any of these. That there is such a thing as quantum chemistry, scientists have known for quite a while; but this…this is something else. It’s in between what we knew about individual nuclear particles and the much larger world of molecular chemistry (which itself is a smaller world inside the world we see as physical reality). We’re just beginning to get a fix on the existence of this ‘world’ of molecular quantum chemistry, and the minds of scientists boggle at the implications. For example, here’s a typically reserved statement from the research:

…a key to advancing biology, creating new materials, producing energy and other research areas. The new JILA work also will aid studies of quantum gases (in which particles behave like waves) and exotic physics spanning the quantum and macroscopic worlds. It may provide practical tools for “designer chemistry” and other applications such as precision measurements and quantum computing.

Is there anything this doesn’t cover? Not really. Quantum physics underlies everything, so unless its effects are trivial, it affects everything. The ability to manipulate quantum chemistry means that in some way, almost any kind of physical material or process is fair game. Among other things, just the other week scientists announced the discovery that plants are (since long ago) using quantum mechanics in photosynthesis. Where else? What Nature does; science and technology usually try to imitate (hominid see, hominid do).

It takes one hell of…wrong metaphor…one cool thermometer. Such a thermometer is not like you might imagine – like a mercury tube on a stick. Like so much very subtle science, the temperature is derived indirectly from other measurements, in this case from magnetic readings.

Now a team of physicists has devised a thermometer that can potentially measure temperatures as low as tens of trillionths of a degree above absolute zero. Their experiment is reported in the current issue of Physical Review Letters and highlighted with a Viewpoint in the December 7 issue of Physics.

A team at the MIT-Harvard Center for Ultra-Cold Atoms has developed a thermometer that can work in this unprecedentedly cold regime. The trick is to place the system in a magnetic field, and then measure the atoms’ average magnetization. By determining a handful of easily-measured properties, the physicists extracted the temperature of the system from the magnetization. While they demonstrated the method on atoms cooled to one billionth of a degree, they also showed that it should work for atoms hundreds of times cooler, meaning the thermometer will be an invaluable tool for physicists pushing the cold frontier.

[Source: EurekAlert]

As materials – and their atoms – approach absolute zero, they begin to act differently. At some point, quantum forces come to the fore, and with them come behaviors that are unusual (from the normal scientific perspective) and incredibly interesting. Count superconductivity, superfluidity, and Bose-Einstein condensation among those interesting things.