Quantum computers are the next major leap in computing, bringing the peculiar properties of quantum mechanics to the operations of computers. They run on qubits – quantum bits – which can be used to do calculations much faster than regular computer bits. There are hurdles to overcome though, and one of them is to make sure that the qubits do not accumulate errors.
Qubits are particularly sensitive to heat and radiation, so the ideal setup would be able to reset the qubits after a calculation. One approach is to cool them down to just a fraction of a degree above absolute zero and keep them there. Most state-of-the-art techniques can bring qubits to 40 to 49 milliKelvins, a few hundredths of a degree above absolute zero.
Work presented in a new paper has gone even further. Their quantum absorption refrigerator is formed using superconducting circuits and can cool a qubit to 22 milliKelvins, which massively reduces the chance for errors from the get-go.
“In a quantum computer, initial errors can compound as the calculation proceeds,” first author Mohammed Ali Aamir, from Chalmers University of Technology, said in a statement. “The more you can get rid of them at the outset, the more effort you will save later.”
The dramatic cooling delivered to the qubits is like wiping clean a whiteboard, so that the qubit can be used anew, without the worry about errors.
“If you didn’t cool the qubit to that low a temperature, you wouldn’t be able to erase the board as thoroughly,” explained Nicole Yunger Halpern, a physicist at NIST and the University of Maryland’s Joint Center for Quantum Information and Computer Science.
“We think this approach will pave the way for more reliable quantum computing,” Ali said. “It’s hard to manage errors in quantum computers right now. Beginning closer to the ground state will compound into fewer errors you’d need to correct down the line, reducing errors before they occur.”
The quantum refrigerator also uses qubits, one that is connected to a hotter part of the system and is the power supply, and another that is a heat sink, where the heat of the actual computational qubit would go in the refrigeration process. The approach works autonomously and this is why the team is excited to have developed such an approach.
“The technique in this paper could benefit quantum computers,” added Yunger Halpern. “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. It could introduce technological capabilities we haven’t even thought of yet.”
A paper discussing the results is published in the journal Nature Physics.
