Quantum computing promises to revolutionize how we solve problems in personalized medicine, new technologies, and even artificial intelligence. Although there are many challenges before we get there, an important step forward has been announced.
Researchers from Aalto University in Finland have reported in Nature Communications a functioning quantum refrigerator that can be used on many different quantum systems. Quantum computers use quantum processes (qubits) to do calculations, and even subtle changes (like a bit more heat) can create mistakes. The refrigerator turns down the heat in a system, thus preventing some errors to occur.
“One of the basic criteria that a working quantum computer must satisfy is that there has to be a way to accurately initialize its memory,” group leader Dr Mikko Möttönen told IFLScience. “In practice, this means that we must be able to accurately take the quantum bits, or qubits, to their ground state.”
Unfortunately, you can’t get to the perfect ground states because that means a zero temperature. Although that’s an ideal condition, getting close to it is good enough. Errors go down exponentially, so low temperatures are fine for quantum computing. Low-temperature initialization is the best way to avoid set-up errors that propagate through the system.
“With our new refrigerator, we think that is should be possible to reset qubits very accurately to their ground states in just a couple of tens of nanoseconds,” Möttönen added.
The system uses a method called single-electron tunneling from a metal to a superconductor, a material that has no electrical resistance. Electrons need a bit of a push to jump into the superconductor and that extra bit of energy comes from the quantum system.
People familiar with superconductors know that their extraordinary properties only happen at really low temperatures. At least for now. The researchers do think this refrigerating technique can be applied to any superconductor, but until somebody creates a room-temperature superconductor, we can only speculate.
While the refrigerator results are exciting, there’s still work to be done to perfect this technology. The team will also test it with actual qubit configurations.
“Thus far we have also only shown that we can turn the cooling on and off but not how fast,” Möttönen continued. “We want to be able to do this in nanosecond timescales for qubits. Again, we do not see any obstacles here and are currently working on an experiment showing that the fridge is very fast as well.”
Quantum computers have a truly tremendous potential, but the challenges to get to those working machines are still many. For now, it remains an exciting field at the cutting-edge of physics and computer science.