EPFL engineers have invented a tool that can convert heat into electrical power proficiently at temperatures even colder than those in outer space. This advancement could significantly propel quantum computing technologies by tackling a major hurdle.
In order to conduct quantum calculations, quantum bits (qubits) must be cooled to temperatures within the millikelvin spectrum (close to -273 degrees Celsius) to decrease atomic movement and decrease disruptions. However, the electronic systems utilized to govern these quantum circuits produce heat, which is troublesome to dissipate at such low temperatures. As a result, most present technologies need to segregate the quantum circuits from their electronic constituents, leading to disruptions and inefficiencies that hinder the progression of larger quantum systems beyond the laboratory.
Scientists at EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), under the leadership of Andras Kis, in the School of Engineering have now engineered a tool that not only functions at extremely low temperatures, but does so with effectiveness comparable to present technologies at room temperature.
“We are the first to create a tool that matches the conversion efficiency of current technologies, but that functions at the low magnetic fields and ultra-low temperatures required for quantum systems. This work is truly a step ahead,” expressed LANES PhD student Gabriele Pasquale.
The groundbreaking tool combines the exceptional electrical conductivity of graphene with the semiconductor attributes of indium selenide. Being only a few atoms thick, it behaves like a two-dimensional entity, and this novel amalgamation of materials and structure contributes to its unparalleled performance. The breakthrough has been featured in Nature Nanotechnology.
Capitalizing on the Nernst phenomenon
This tool leverages the Nernst phenomenon: a sophisticated thermoelectric occurrence that produces an electrical voltage when a magnetic field is implemented perpendicular to an entity with a varying temperature. The two-dimensional setup of the lab’s tool allows the efficiency of this mechanism to be regulated electrically.
The 2D configuration was produced at the EPFL Center for MicroNanoTechnology and the LANES lab. The experiments entailed utilizing a laser as a heat source, and a specialized dilution refrigerator to achieve 100 millikelvin – a temperature even colder than outer space. Transforming heat into voltage at such low temperatures is typically highly demanding, but the novel tool and its exploitation of the Nernst phenomenon make this feasible, bridging a pivotal gap in quantum technology.
“If you think of a laptop in a cold office, the laptop will still heat up as it operates, causing the temperature of the room to increase as well. In quantum computing systems, there is currently no mechanism to prevent this heat from disturbing the qubits. Our tool could provide this necessary cooling,” Pasquale mentioned.
An individual specializing in physics, Pasquale highlights that this study is notable because it sheds light on thermopower conversion at low temperatures – an underestimated occurrence until now. Given the high conversion efficiency and the use of potentially manufacturable electronic components, the LANES team also believes their tool could already be integrated into existing low-temperature quantum circuits.
“These findings mark a significant progression in nanotechnology and hold potential for developing advanced cooling technologies imperative for quantum computing at millikelvin temperatures,” Pasquale emphasized. “We firmly believe this accomplishment could transform cooling systems for forthcoming 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, 2 July 2024, Nature Nanotechnology.
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