“Getting to the Starting Line”: Achieving the Bose-Einstein Condensate

For five years Professor Seth Aubin and graduate students Megan Ivory and Austin Ziltz have been working towards achieving the Bose-Einstein Condensate (BEC), a unique state of matter of gas achieved at ultra-cold temperatures.

Rather than producing experimental results as most other experimental labs on campus do, the Ultra-Cold lab has been undergoing a feat of engineering just to “get to the starting line”. At least 75% of the rather impressive experimental set-up was built by hand or modified by the lab group to attain the extremely cold temperatures needed just to begin to be in the range of the critical temperature (Tc) for the Bose-Einstein Condensate. Joining the Ultra-Cold Atomic, Molecular and Optics (AMO) lab didn’t just provide experience in that field according to Megan; working towards the BEC has provided experience with electronics, vacuum and laser science (yes, laser science- as lasers are actually incredibly ordered, they are also incredibly cold and can be used to cool matter). What’s more, this is all before the intended experiments could even begin.

Knowing that most of the equipment you rely on was created by your own hands can add a bit of pressure to the situation. “How many things that we built have to go right and not break themselves?” wondered Austin, thinking on all the electronics projects he worked on for the BEC set-up. If something goes wrong, there is no manufacturer to get a replacement from or lodge a complaint with, after all. “There was lots of finger crossing.”

When it all goes right, though, it’s an indescribably thing, and that is exactly what the lab got to experience upon attaining the BEC. At first it felt a bit bittersweet, Austin explains, because the first glimpse of the BEC occurred late at night when only Professor Aubin was present. The pictures were blurry, however, so all three were present for the first proper pictures taken of the BEC. When asked how he felt upon attaining the BEC, Austin’s first response was a very honest, “tired.” However, once people started coming into the lab to see it, it became increasingly exciting

What makes the BEC so significant? Well, for one (very cool) thing, it is quantum mechanics you can literally observe. “Learning it all is abstract,” Megan states, “but for the BEC you can literally see it on screen.”

But that’s getting just a bit ahead of ourselves.

The Bose-Einstein Condensate occurs at extremely low temperatures close to 0 Kelvin; Aubin’s lab attains temperatures between 10 to 100 nanoKelvin (that’s 1×10-7 Kelvin). At such low temperatures the atoms in the gas statistically prefer to be in the ground state, or the unexcited state with no energy added. The trademark of the BEC is the cigar-like shape it makes when atoms cooled to the critical temperature are kept in a bowl-shaped trap. The atoms are bounded on three sides, but they are tightly bound on only two in the horizontal direction; as a result, when the trap is turned off and the atom cluster begins to fall due to gravity, it rapidly expands in two directions (the tightly-bounded two), but not in the loosely bounded one. This is due to the basic quantum mechanical equation . This shift from cigar-shaped cluster to elongated ‘blob’, for lack of a better word, is the key signature, and can be seen in the gif below.

The above image links to a video of the BEC trapped on an atom chip provided to the College by the Thywissen Group at the University of Toronto.

The Bose-Einstein Condensate is an interesting type of matter due to the fact that all the atoms are identical as they have all gone to the ground state; it’s idea for controlled conditions. Now that it is attained Aubin’s lab will proceed with experiments that utilize its unique nature. The study of the BEC can lead to innovations in other areas, too, including quantum computing and atomic clocks. For now, the lab is working on increasing the quantity of atoms kept in the trap when the BEC is excited and on getting BEC using potassium atoms as well as the already-successful rubidium atoms.

Attaining the BEC is just the beginning for Aubin’s lab. As he said, all the work up to this point has been getting to the starting line. As far as starting lines go, though, it really is quite an impressive one.

For additional information about Aubin’s lab and research, you can visit his site here. For further reading about attaining the BEC at William and Mary,read Joseph McClain’s article on the physics department page here.

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