The breakthrough can revolutionize quantum computing. Engineers at the École Polytechnique Fédérale de Lausanne have developed a device that efficiently transforms heat into electrical voltage at temperatures lower than that of outer space. This invention solves one of the major paradoxes in the development of quantum computing technology.
Qubits must, however, be cooled to millikelvin temperatures—near -273 degrees Celsius—to reduce atomic motion and minimize noise. However, all of the electronics that manage these quantum circuits are significant heat sources, which is difficult to remove at low temperatures. State-of-the-art approaches offten separate quantum circuits from their electronic components at the expense of introducing noise and inefficiencies that limit the scaling of quantum systems beyond the laboratory.
The EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), led by Andras Kis, has developed a device that does not work only at these extremely low temperatures but with efficiency comparable to that of conventional technologies operating at room temperature. “We are the first to create a device that matches the conversion efficiency of current technologies, but that operates at the low magnetic fields and ultra-low temperatures required for quantum systems. This work is truly a step ahead,” said LANES PhD student Gabriele Pasquale.
The device brings together the high electrical conductivity of graphene and the semiconductor properties of indium selenide in an innovative way. Only a few atoms thick, it behaves like a two-dimensional object, making the novel combination of materials and structure provide its unprecedented performance. The work is published in Nature Nanotechnology.
Said device exploits an effect known as the Nernst effect, a more complex thermoelectric phenomenon that creates an electrical voltage under a magnetic field applied perpendicular to an object with a temperature gradient. Thanks to the two-dimensional nature of the lab’s new device, it is now possible to electrically control the efficiency of such a mechanism.
The 2D structure was fabricated at the EPFL Center for MicroNanoTechnology and the LANES lab. This was then tested using a laser as a heat source and a specialized dilution refrigerator to reach 100 millikelvins, a temperature even colder than outer space. Normally, such a conversion of voltage from heat at very low temperatures is not easy; however, with the new device and the harnessing of the Nernst effect contemporaneously, this becomes feasible, filling a gap that has been critical up until now in quantum technology.
Pasquale explained that just as a laptop heats up a cold office, causing the room’s temperature to rise, quantum computing systems currently lack a mechanism to prevent this heat from disturbing the qubits. The new device could provide the necessary cooling to maintain the integrity of quantum computations.
He added that what the work did was bring to the foreground a totally under-explored phenomenon: low-temperature thermopower conversion. With this high conversion efficiency, the use of electronic components is possibly manufacturable, according to the LANES team, their device should already be able to integrate with 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,” Pasquale said. “We believe this achievement could revolutionize cooling systems for future technologies.”
This breakthrough not only created a huge stride in quantum computing but has brought forward a new frontier of research and development in nanotechnology and physics at ultra-low temperatures.