Engineers at EPFL have created an innovative device that can turn heat into electrical voltage at temperatures even colder than outer space.
This new technology could solve a major problem in quantum computing, which needs extremely low temperatures to work effectively.
Quantum computers use quantum bits, or qubits, which need to be cooled to temperatures near -273 degrees Celsius (millikelvin range).
This cooling is essential to slow down atomic motion and reduce noise, allowing the qubits to function properly.
However, the electronics that control these quantum circuits produce heat, which is very difficult to remove at such low temperatures.
This issue forces current technologies to separate the quantum circuits from their electronic components, leading to inefficiencies and noise that hinder the development of larger quantum systems.
The team at EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), led by Andras Kis, has developed a device that operates efficiently at these extremely low temperatures, similar to how current technologies work at room temperature.
Their groundbreaking work has been published in the journal Nature Nanotechnology.
“We are the first to create a device that matches the conversion efficiency of current technologies but operates at the low magnetic fields and ultra-low temperatures needed for quantum systems.
This is a significant step forward,” says LANES Ph.D. student Gabriele Pasquale.
This new device uses the excellent electrical conductivity of graphene combined with the semiconductor properties of indium selenide. The device is only a few atoms thick, behaving as a two-dimensional object, which is key to its exceptional performance.
The device takes advantage of the Nernst effect, a thermoelectric phenomenon that creates an electrical voltage when a magnetic field is applied perpendicular to an object with a temperature gradient. The 2D nature of the device allows this effect to be controlled electrically, enhancing its efficiency.
The 2D structure was created at the EPFL Center for MicroNanoTechnology and the LANES lab. During experiments, researchers used a laser as a heat source and a special dilution refrigerator to cool the device to 100 millikelvin, colder than outer space.
Converting heat to voltage at such low temperatures is usually very challenging, but this device makes it possible by harnessing the Nernst effect.
“If you think of a laptop in a cold office, the laptop will still heat up as it operates, causing the room to warm up too. In quantum computing systems, there is currently no way to prevent this heat from disturbing the qubits. Our device could provide the necessary cooling,” explains Pasquale.
Pasquale, a physicist, highlights that this research is important because it explores thermopower conversion at low temperatures, a relatively unknown phenomenon. Given its high conversion efficiency and the use of potentially manufacturable electronic components, the LANES team believes their device could soon be integrated into existing low-temperature quantum circuits.
“These findings represent a major advancement in nanotechnology and hold promise for developing advanced cooling technologies essential for quantum computing at millikelvin temperatures,” says Pasquale.
“We believe this achievement could revolutionize cooling systems for future technologies.”
