Quantum molecules are a possibility, shows a new study by physicists at the University of Chicago

Physicists have always wanted to influence and control quantum molecules for success in doing so would result in technology feats like earthquake sensors which can change our lifestyle for the better. It had been a long-sought dream of atomic physicists to bring multiple molecules together in a single quantum state and researchers at the University of Chicago succeeded in doing so. 

Image of the molecules successfully pooled into a Bose-Einstein condensate.

Scientists at the University of Chicago just published a paper on April 28th in Nature, which states a methodology used to bring multiple molecules together in a single quantum state. This success opens doors to many more discoveries and progression in the field of quantum physics. 

“People have been trying to do this for decades, so we're very excited.” The senior author and professor of physics at the University of Chicago, Cheng Chin said “I hope this can open new fields in many-body quantum chemistry. There's evidence that there are a lot of discoveries waiting out there.” 

But it would be wrong to say that this is the first time scientists have been able to put together many particles in one quantum state. We have been doing it for years with clouds of single atoms which we call bose-einstein condensate. Bose-Einstein condensate is a state of matter which is formed when low-density boson gases are cooled at near absolute zero temperatures. Because the atoms are cooled at near-zero degrees, they reach their lowest-energy state, eventually overlapping in quantum superposition. This results in a bunch of high-density atoms which in unison act like one “super atom”.

But these were atoms, molecules are a tougher nut to crack. "Atoms are simple spherical objects, whereas molecules can vibrate, rotate, carry small magnets," Chin explained. "Because molecules can do so many things, it makes them more useful, and much harder to control." What this means is that since molecules are much bigger than atoms, they are much more complex than atoms as they can vibrate, move around or behave like magnets. The complexity of molecules makes them much more difficult to control, but it is also the reason making them much more useful. 

To harness molecules, Chin and his team took on the challenge of creating a molecular Bose-Einstein condensate. They started their journey with a simple bose Einstein condensate using thousands of cesium atoms and cooling it even further to increase the magnetic field. An increase in the magnetic field would lead to 15 percent of the cesium atoms forming cesium molecules by binding together. The rest of the “unbounded” atoms were spewed out and a magnetic field gradient was applied to hover the molecules. These molecules were then constrained in a two-dimensional configuration. 

"Typically, molecules want to move in all directions, and if you allow that, they are much less stable," Chin said. "We confined the molecules so that they are on a 2D surface and can only move in two directions."

Chin and his team observed that the resulting gas of this experiment was crafted out of molecules having the same quantum state with the same orientation, spin, and even vibration!

So far, they have been able to link a few thousand molecules together in such a state and are still experimenting with its potential. Exploring the fundamental working behind molecular bose-einstein condensate might help scientists to create condensates with different molecules which might inherit the properties that might possess unique technological applications.

"In the traditional way to think about chemistry, you think about a few atoms and molecules colliding and forming a new molecule," Chin said. "But in the quantum regime, all molecules act together, in collective behavior. This opens a whole new way to explore how molecules can all react together to become a new kind of molecule.

"This has been a goal of mine since I was a student," he added, "so we're very, very happy about this result."

Even though there is a long road to travel, this has opened doors to many more experiments. It has shown us the glimmer of hope that quantum molecules are a possibility. On top of it all, Chin and his team have shown us what the future beholds. 

The research paper was published in the journal The nature.

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