For the first time, a quantum engine has outperformed its traditional equivalent, without any special tweaks to its environment.
The device harnesses the weird physics of very small objects to produce more power than a standard, or classical, engine under the same conditions, scientists report in the March 22 Physical Review Letters.
“Theyve shown very convincingly that the quantum machine performs better than the classical,” says physicist Mark Mitchison of Trinity College Dublin. “Its a very important step forward.”
The device is a type of engine called a heat engine. Traditional heat engines turn heat into motion. For example, a cars internal combustion engine burns fuel to move pistons up and down, resulting in the car moving forward. Other heat engines have boasted power increases. But those machines relied on tweaks to the environment outside the main machine — for example, the machines heat source may have been imbued with beneficial properties — so the extra power wasnt entirely a feature of the machine itself.
In the new study, the quantum engine works not by igniting gasoline, but by using a laser to cause an electron within a tiny defect of a diamond crystal to jump between energy levels. And instead of moving pistons, the quantum machine outputs its power in electromagnetic waves.
Heres where the quantum part comes in: Objects that behave according to quantum mechanics are sometimes found in a limbo known as superposition, meaning theyre caught in two places at once, or in two different configurations. The electron in the quantum engine can be in a superposition of two energy levels. Its as if a car engines piston was simultaneously in the up and down positions.
Under certain conditions, that property, the scientists report, results in increased power output as compared with the maximum power possible with a traditional heat engine. “This is the first experiment where this kind of regime was reached,” says physicist Roberto Serra of the Federal University of ABC in Santo André, Brazil.
But the researchers “don't have a complete characterization of the quantum engine,” Serra says. The team estimated the engines output power, but not other qualities, such as efficiency. So future experiments should further investigate this type of machine, he says.
The quantum power boost shows up only when the engine is operated extremely gently, like a car engine in which the pistons move only slightly during each cycle. That means the quantumRead More – Source