Quantum gates in 6.8 nanoseconds: Jülich team sets a speed record
Jülich researchers perform computing steps on superconducting qubits in 6.8 nanoseconds – with an accuracy of more than 99.98 percent.
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Quantum computers have to carry out their computing steps quickly, before disturbances destroy the fragile quantum states. A team at Forschungszentrum Jülich has now demonstrated single-qubit gates on superconducting qubits lasting just 6.8 nanoseconds; such systems typically need several tens of nanoseconds. In that time, light travels about two metres. The work has been published in the journal Nature Communications; the research centre presented it on 23 October.
Fast pulses have a catch: through so-called multiphoton transitions, they can push the qubit into higher energy states that are not meant to be part of the computation. The team developed a method that specifically suppresses such transitions. Their probability fell by a factor of more than 20 compared with the previous standard method. The probability of the qubit unintentionally leaving its computational states during an operation is below 0.002 percent. Accuracies of 99.981 and 99.989 percent were measured for two fundamental operations.
The work involved the experimental group of Rami Barends and the theory group of Felix Motzoi at the research centre's Peter Grünberg Institute. The results were obtained in the collaborative project QSolid, which is working on a quantum computer made in Germany.