Researchers have big ideas about the potential of quantum technology, from non-hackable networks to earthquake sensors. But it all depends on one major technological achievement: being able to build and control systems of quantum particles, which are among the smallest objects in the universe.
This goal is now a step further with the publication of a new method by scientists at the University of Chicago. Posted on April 28 in Nature, the article shows how to bring several molecules at once into a single quantum state – one of the most important goals of quantum physics.
“People have been trying to do this for decades, so we’re very excited,” said lead author Cheng Chin, professor of physics at UChicago, who said he wanted to achieve this since he was a graduate student. in the 1990s. “I hope this can open up new areas in quantum chemistry to multiple bodies. There is evidence that there are a lot of discoveries waiting there.
One of the essential states of matter is called a Bose-Einstein condensate: when a group of particles cooled to near absolute zero share a quantum state, the entire group begins to behave as if it were ‘just one atom. It’s a bit like persuading an entire group to walk in full step while playing in tune – hard to achieve, but when that happens a whole new world of possibilities can open up.
Scientists have been able to do this with atoms for a few decades, but what they would really like to do is be able to do it with molecules. Such a breakthrough could serve as the foundation for many forms of quantum technology.
But since molecules are larger than atoms and have many more moving parts, most attempts to mine them have dissolved into chaos. “Atoms are simple spherical objects, whereas molecules can vibrate, rotate, carry small magnets,” Chin said. “Because molecules can do so many different things, it makes them more useful and at the same time a lot harder to control.”
Chin’s group wanted to take advantage of some new lab capabilities that had recently become available. Last year they started experimenting with adding two conditions.
The first was to cool the whole system even more – down to 10 nanokelvins, a hair split above absolute zero. Then they packed the molecules in a crawl space so that they were pinned flat. “As a rule, molecules want to move in all directions, and if you allow that, they’re much less stable,” Chin said. “We have confined the molecules so that they are on a 2D surface and can only move in two directions.”
The result was a set of virtually identical molecules – aligned with exactly the same orientation, the same vibrational frequency, in the same quantum state.
Scientists described this molecular condensate as a blank sheet of new quantum engineering drawing paper. “It’s the absolute ideal starting point,” Chin said. “For example, if you want to create quantum systems to hold information, you need a blank slate to write on before you can format and store that information.”
So far, they have been able to link up to a few thousand molecules together in such a state and are starting to explore its potential.
“In the traditional way of thinking about chemistry, you think of a few atoms and molecules that collide and form a new molecule,” Chin said. “But in the quantum regime, all the molecules act together, in a collective behavior. This opens up a whole new way to explore how molecules can all react together to become a new type of molecule.
“It’s been one of my goals since I was a student,” he added, “so we’re very, very happy with this result.”
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