Aalto University Researchers Create Nanorefrigerator for Quantum Computers

A team of researchers from Aalto University have invented a quantum-circuit refrigerator, which according to the team, can help reduce errors in quantum computing.

Quantum computers differ from present-day computers in the sense that they use quantum bits, or qubits, for computation purpose. A qubit can exist in both zero and one state simultaneously compared to normal bits which means either zeros or ones. This versatility of qubits however makes them sensitive to external perturbations.

According to researchers, a quantum computer also needs a cooling mechanism. In the beginning of the computation, every qubit is reset, and they are too hot, they cannot be reset. Quantum physicist Mikko Möttönen and his team at Aalto University have now found the solution of this problem. They have developed a nanoscale refrigerator which helps researchers quickly initialize most electrical quantum devices. The new invention involves a small Silicon chip with two parallel superconducting oscillators and the quantum-circuit refrigerators connected to them.

“I have worked on this gadget for five years and it finally works!” said Kuan Yen Tan, who works as a postdoctoral researcher in Möttönen’s group.

Tan utilized the tunneling of single electrons through a two-nanometer-thick insulator to cool down a qubit-like superconducting resonator. An external voltage source gave the electrons slightly too little energy than required for direct tunneling. The result is that the electron absorbs the missing energy from the nearby quantum device, which makes the device cool down.

“Our refrigerator keeps quanta in order,” Mikko Möttönen said.

The team is now planning to cool actual quantum bits in addition to resonators. They also want to lower the minimum temperature achievable with the refrigerator.

The detailed findings of the study have been published in the scientific journal, Nature Communications.