Illustration of the filtering of unwanted quasiparticles (red spheres) from a stream of superconducting electron pairs (blue spheres) using a microwave-driven pump. Credit: Copyright Philip Krantz, Krantz NanoArt
An international team has succeeded in making further improvements to the lifetime of superconducting quantum circuits. An important prerequisite for the realization of high-performance quantum computers is that the stored data should remain intact for as long as possible. Researchers have developed and tested a technique that removes unpaired electrons from the circuits. These are known to shorten the qubit lifetime (to be published online by the journal Science today.
Superconducting circuits belong to the most promising candidates for implementing quantum bits, ie qubits, with which quantum computers can store and process information. The high error rates associated with previously available qubits have up to now limited the size and efficiency of quantum computers. Dr. Gianluigi Catelani of the Peter Grünberg Institute (PGI-2) in Jülich and his colleagues has now found a way to prolong the time in which the superconducting circuits are able to store a “0” or a “1” without errors.
When superconducting materials are cooled below a material-specific critical temperature, electrons form pairs; then current can flow without resistance. However, so far it has not been possible to build superconducting circuits in which all electrons bundle together. Single electrons remain unpaired and are unable to flow without resistance. Due to these quasiparticles, energy is lost which limits the length of time circuits can store data.
Researchers have now developed and tested a technique that can temporarily remove unpaired electrons away from the circuit; with the help of microwave pulses, they are in effect “pumped out”. This results in a 3X improvement in the lifespan of qubits.
“The technique can in principle be put to immediate use for all superconducting qubits”, explained Catelani. However, he emphasised that the lifespan of qubits is only one of many hurdles in the development of complex quantum computers. Moreover, the new technique means that the quasiparticles are not permanently removed, but flow back again and again. The scientists have another solution ready to solve this problem: the pumping technique can be combined with another method that permanently traps the quasiparticles. Their results were published in Physical Review B (DOI: 10.1103/PhysRevB.94.104516). http://www.alphagalileo.org/ViewItem.aspx?ItemId=170834&CultureCode=en
Recent Comments