Conventional heat engines and fridges work by associating two pools of fluid. Compressing one pool makes its fluid to heat up while quickly expanding the other pool cools its liquid. If these tasks are done in a periodic cycle, the pools will exchange energy, and the system can be utilized as either a heat engine or a fridge.
RIKEN engineers have recently engineered a quantum nanodevice that can simultaneously act as a heat engine and a refrigerator.
This multitasking nanomachine uses an electron in a semiconductor. The electron has two potential energy states. The group could increase or decrease the gap between these energy states by applying an electric field and microwaves.
Keiji Ono of the RIKEN Advanced Device Laboratory said, “This can be analogous to the periodic expanding–compressing operation of a fluid in a chamber. The device also emitted microwaves when the electron went from the high-energy level to the lower one.”
The group previously showed that the nanodevice could go about as either a heat engine or as a fridge by observing whether the upper energy level was occupied. However, at that point, they demonstrated something surprising—the nanomachine could act as both simultaneously, which is a purely quantum effect.
Engineers confirmed this by observing the upper energy level occupancy, which combined to create a characteristic interference pattern.
Ono said, “There was an almost perfect match between the experimental interference pattern and that predicted by theory.”
“This may allow rapid switching between the two modes of operation. This ability could help create novel applications with such systems in the future.”
- K. Ono et al. Analog of a Quantum Heat Engine Using a Single-Spin Qubit, Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.125.166802