Quantum refrigerator cools qubits to record low temperatures

A quantum refrigerator cools qubits to extremely low temperatures, reducing errors and improving quantum computer performance.

The device, developed by a team including scientists from the National Institute of Standards and Technology (NIST) and Sweden’s Chalmers University of Technology, can cool quantum bits – qubits – to record-low temperatures, reducing errors in calculations.

Quantum computers rely on qubits to perform calculations, but these delicate units are prone to errors caused by heat and radiation.

The new quantum refrigerator solves this problem, acting like an eraser wiping the “chalkboard” clean by cooling qubits to a fraction of a degree above absolute zero (-273.15 °C or -459.67 °F), ensuring they start calculation in an error-free state.

The method uses two qubits – one hot and one cold – to cool a third, target qubit. One qubit absorbs heat from a warm environment, while the other acts as a heat sink, transferring excess energy away from the target qubit.

This autonomous process requires minimal external control, making it a practical tool for maintaining low temperatures in quantum computers.

Nicole Yunger Halpern, a physicist at NIST, highlighted the potential impact of this method on quantum computing.

“It could address one of the problems in quantum computer design, and it also shows that we can siphon heat from one part of the computer’s refrigerator and convert the heat into work,” she said. “It could introduce technological capabilities we haven’t even thought of yet.”

The team’s research, published in Nature Physics, demonstrates that their quantum refrigerator can cool qubits to 22 millikelvins (mK), significantly lower than the 40-49 mK achieved by current methods.

According to Aamir Ali of Chalmers University, this deeper cooling will help reduce errors from the start of quantum calculations.

“In a quantum computer, initial errors can compound as the calculation proceeds,” Ali explained.

“The more you can get rid of them at the outset, the more effort you will save later.”

Superconducting circuits, which were used to build the qubits in this study, are among the most promising materials for creating reliable quantum computers.

In traditional refrigerators, electricity powers the cooling process. In this quantum fridge, however, the system uses heat from the computer itself to power the cooling process. By efficiently transferring heat away from the computational qubit, the system ensures that the qubit is reset to its lowest energy state, or ground state, before calculations begin.

Researchers believe this breakthrough could pave the way for more reliable quantum computers, capable of performing tasks beyond the reach of conventional computers.

“We think this approach will pave the way for more reliable quantum computing,” Ali said.

“Beginning closer to the ground state will compound into fewer errors you’d need to correct down the line, reducing errors before they occur.”