Scientists observe atoms' unexpected behaviour, in tune with Quantum Physics

Physicists at Harvard University have created a quantum gas microscope that can be used to observe single atoms at temperatures so low the particles follow the rules of quantum mechanics, behaving in bizarre ways, the university said Wednesday.

The work, published this week in the journal Nature, represents the first time scientists have detected single atoms in a crystalline structure made solely of light, called a Bose Hubbard optical lattice. It’s part of scientists’ efforts to use ultra-cold quantum gases to understand and develop novel quantum materials.

“Ultra-cold atoms in optical lattices can be used as a model to help understand the physics behind superconductivity or quantum magnetism, for example,” says senior author Markus Greiner, an assistant professor of physics at Harvard and an affiliate of the Harvard—MIT Center for Ultra-cold Atoms.

The quantum gas microscope developed by Greiner and his colleagues is a high-resolution device capable of viewing single atoms - In this case, atoms of rubidium - occupying individual, closely spaced lattice sites. The rubidium atoms are cooled to just 5 billionths of a degree above absolute zero (—273 degrees Celsius).

“At such low temperatures, atoms follow the rules of quantum mechanics, causing them to behave in very unexpected ways,” explains first author Waseem S. Bakr, a graduate student in Harvard’s Department of Physics. “Quantum mechanics allows atoms to quickly tunnel around within the lattice, move around with no resistance, and even be ‘delocalized’ over the entire lattice. With our microscope we can individually observe tens of thousands of atoms working together to perform these amazing feats.” In their paper, Bakr, Greiner and colleagues present images of single rubidium atoms confined to an optical lattice created through projections of a laser-generated holographic pattern. The neighbouring rubidium atoms are just 640 nanometers apart, allowing them to quickly tunnel their way through the lattice.

The new microscope’s ability to detect arrays of thousands of single atoms gives scientists what amounts to a new workshop for tinkering with the fundamental properties of matter, making it possible to study these simulated systems in much more detail, and possibly also forming the basis of a single-site readout system for quantum computation.

“There are many unsolved questions regarding quantum materials, such as high-temperature superconductors that lose all electrical resistance if they are cooled to moderate temperatures,” Greiner says.

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