Quantum Engines Powered by a Look express
In the quantum world, particles can walk through walls: this is quantum tunneling. If you place a detector right in the path of such a 'ghostly' passage, the moment of detection acts like a starting pistol: the particle gets a sharp kick and flies out of the barrier with excess energy, turning into a tiny engine. The device needs no batteries or external voltage — the observation itself serves as fuel.
This engine obeys the strict laws of thermodynamics and can simultaneously heat and cool its surroundings. In a certain regime, it reaches a 'dark state'—ceasing to exchange heat with the outside world, as if vanishing for any thermometer. Such motors, inspired by methods of spectroscopy, could one day power nanorobots or cool quantum computers simply by existing.
As John von Neumann predicted, measurement is a physical action, and now it literally becomes fuel.
Original abstract
as written by the authors arXiv:2510.22394
Quantum tunneling allows electrons to be transferred between two regions separated by an energetically forbidden barrier. Performing a position measurement that finds a particle in the barrier forces the tunneling electrons to transition from having a classically forbidden energy to an energy above the barrier height. We exploit this effect to define quantum tunneling engines that can use the unconditioned detection of virtually occupied states as a resource for power generation and cooling. Leveraging energy exchange with the detector, we show that the device can operate in a hybrid regime, enabling simultaneous cooling and power generation. Furthermore, we demonstrate measurement-assisted autonomous refrigeration and "checkpoint" cooling driven purely by a thermal bias, without the need for an applied potential. We also find a "purification-by-noise" effect when the measurement drives the system into a stationary dark state. These results underscore the intriguing dual role of measurement as a thermodynamic resource and a dark state generator.
Without the tunnel effect, the Sun wouldn't shine: protons couldn't overcome electric repulsion and fuse into helium: it's tunneling that kick-starts thermonuclear fusion in stars.