Scientists develop efficient 2D quantum cooling device

EPFL scientists have created a groundbreaking device that operates efficiently at the millikelvin temperatures required for quantum computing, potentially revolutionizing high-tech cooling systems. LANES’ 2D device made of graphene and indium selenide. Credit: Alain Herzog

EPFL engineers have developed a device that can efficiently convert heat into electrical voltage at temperatures even lower than those found in space. This breakthrough could significantly accelerate quantum computers technology by solving a major obstacle.

To perform quantum computations, quantum bits (qubits) must be cooled to temperatures in the millikelvin range (close to -273 degrees) Celsius) to reduce the motion of atoms and minimize noise. However, the electronics used to control these quantum circuits generate heat that is difficult to dissipate at such low temperatures. As a result, most current technologies must separate quantum circuits from their electronic components, which creates noise and inefficiencies that hinder the development of 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 constructed a device that not only operates at extremely low temperatures but also achieves performance comparable to current technologies at room temperature.

“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 excellent electrical conductivity graphene with the semiconducting properties of indium selenide. Being only a few atoms thick, it behaves like a two-dimensional object, and this novel combination of materials and structure provides unprecedented performance. The achievement was published in Nanotechnology in nature.

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. The 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 usually incredibly difficult, but the new device and its use of the Nernst effect make it possible, filling a critical 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 poorly 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.”

Reference: “Electrically Tunable Giant Nernst Effect in Two-Dimensional van der Waals Heterostructures” by Gabriele Pasquale, Zhe Sun, Guilherme Migliato Marega, Kenji Watanabe, Takashi Taniguchi, and Andras Kis, July 2, 2024, Nanotechnology in nature.
DOI: 10.1038/s41565-024-01717-y