Two charged atoms could be used to build a quantum engine and store the energy it produces in a quantum version of a flywheel.
Engines are designed to generate mechanical energy, or 鈥渨ork鈥�. But they only do so in bursts, which makes it challenging to use them for constant motion, like spinning a car鈥檚 wheels. An engine鈥檚 output can be smoothed by adding a flywheel, a device that has enough inertia to spin at a near-constant rate, allowing it to pass along its mechanical energy evenly.
Researchers have previously built engines from quantum ingredients 鈥� single charged atoms, for instance 鈥� but it was never clear whether they could connect to another quantum device and supply it with a steady stream of useful work. at the University of Nottingham in the UK and his colleagues realised these quantum engines needed a quantum flywheel.
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The blueprint for their quantum-engine-plus-flywheel design begins with two electrically charged atoms that are unusually large in diameter. Lesanovsky says they chose so-called Rydberg ions because they can be precisely controlled with lasers and will remain in a desired quantum state when 鈥渢rapped鈥� by electromagnetic forces. In fact, the researchers based their mathematical model of the flywheel on past experiments with Rydberg ions of strontium.
The proposed quantum engine has a working cycle that would be controlled using a laser. The energy from the laser prompts electrons in the ions to jump between different quantum states and interact with each other. Crucially, the energy produced at the end of each cycle would make the two ions oscillate, similar to the way a single point on a wheel physically moves back and forth between its highest and lowest position as it rotates. This motion would be steady, and would therefore make it possible for the quantum engine to provide a smooth flow of work, just like a larger conventional engine fitted with a flywheel.
鈥淲e had this picture of, okay, what if you wanted a quantum car and you want to fuel it with this machine. So we really wanted something that oscillates or rotates,鈥� says Lesanovsky.
Research team member at the University of T眉bingen in Germany says because the flywheel would rely on quantum processes, it would store quantities of work that are appropriate for the energy needs of other quantum devices. He says they could adapt the current design to include more Rydberg ions, which are already used in larger numbers in experiments. This would potentially allow the system to benefit from more quantum effects.
鈥淩ydberg ions have very controllable interactions, and you can get them to interact with each other to create complex quantum states that have no kind of classical analogue,鈥� says at Trinity College Dublin in Ireland. However, he does not think quantum flywheels will be integrated onto quantum computers or similar devices any time soon.
鈥淭his wouldn鈥檛 be in the first generation of quantum computers, or probably even the second, this is something potentially very far off. Now, these studies really serve to teach us about the [quantum] behaviour of nature,鈥� he says.
Journal Reference: Physical Review A,
