A single atom can function as either an engine or a fridge

Experiments with a single-atom device help researchers understand what quantum effects come into play when machinery shrinks to the atomic scale. Credit: Aki Honda / Centre for Quantum Technologies, National University of Singapore

Researchers in at Singapore University of Technology and Design (SUTD) have shown that a single atom can function as either an engine or a fridge. Such a device could be engineered into future computers and fuel cells to control energy flows.

The researchers studied the thermodynamics of a single barium atom. They devised a scheme in which lasers move one of the atom’s electrons between two energy levels as part of a cycle, causing some energy to be pushed into the atom’s vibrations. Like a car engine consumes petrol to both move pistons and charge up its battery, the atom uses energy from lasers as fuel to increase its vibrating motion. The atom’s vibrations act like a battery, storing energy that can be extracted later. Rearrange the cycle and the atom acts like a fridge, removing energy from the vibrations.

In either mode of operation, quantum effects show up in correlations between the atom’s electronic states and vibrations. 

The researchers measured the atom’s vibration after applying 2 to 15 cycles. They repeated a given number of cycles up to 150 times, measuring on average how much vibrational energy was present at the end. They could see the vibrational energy increasing when the atom was zapped with an engine cycle, and decreasing when the zaps followed the fridge cycle.

The results were published in the peer-reviewed journal npj Quantum Information.

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