New 2D Quantum Cooling Device Converts Heat to Voltage at Ultra-Low Temperatures

EPFL engineers have created a device that can efficiently convert heat into electrical voltage at temperatures lower than those in space, an innovation that could help overcome a major hurdle in the development of quantum computing technologies that require extremely low temperatures to operate optimally.

To perform quantum computations, quantum bits (qubits) must be cooled to temperatures in the millikelvin range (near minus 273 degrees Celsius) to slow the motion of the atoms and minimize noise. But the electronics used to control these quantum circuits generate heat that is difficult to remove at such low temperatures.

Most current technologies therefore require decoupling quantum circuits from their electronic components, which introduces noise and inefficiency that make it difficult to realize larger quantum systems outside the laboratory.

Scientists at EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), led by Andras Kis, in the School of Engineering, have created a device that not only operates at extremely low temperatures, but does so with efficiency comparable to current technologies at room temperature. The achievement was published in Nanotechnology in nature.

“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 required for quantum systems. This work is truly a step forward,” says LANES PhD student Gabriele Pasquale.

The innovative device combines the excellent electrical conductivity of graphene with the semiconducting properties of indium selenide. At just a few atoms thick, it behaves like a two-dimensional object, and this novel combination of materials and structure provides unprecedented performance.

Using the Nernst Effect

The device uses the Nernst effect: a complex thermoelectric phenomenon that generates an electric voltage when a magnetic field is applied perpendicularly to an object with a changing temperature. The two-dimensional nature of the laboratory device allows the output of this mechanism to be electrically controlled.

The 2D structure was made at EPFL’s Center for MicroNanoTechnology and LANES lab. Experiments involved using a laser as a heat source and a specialized dilution cooler to reach 100 millikelvins—a temperature even colder than space.

Converting heat into voltage at such low temperatures is normally incredibly difficult, but a new device using the Nernst effect makes it possible, filling a major gap in quantum technology.

“If you think of a laptop in a cold office, the laptop will still heat up as it’s working, which will also cause the room temperature to rise. There’s currently no mechanism in quantum computing systems to prevent this heat from disturbing the qubits. Our device could provide that necessary cooling,” Pasquale says.

Pasquale, a physicist by training, emphasizes that this research is significant because it sheds light on thermoelectric conversion at low temperatures, a phenomenon that has been little studied so far. Given the high conversion efficiency and the use of potentially manufacturable electronic components, the LANES team also believes that their device could already be integrated into existing low-temperature quantum circuits.

“These findings represent a significant advance in nanotechnology and offer the promise of advanced cooling technologies needed for quantum computing at millikelvin temperatures,” says Pasquale. “We believe this achievement could revolutionize cooling systems for future technologies.”