Jülich team sets a speed record for accurate superconducting qubit gates

[Emma29]

A German team has made superconducting qubit gates much faster without losing accuracy. Forschungszentrum Jülich reports that researchers from Jülich, Aachen and Cologne ran single qubit gates on a transmon in just 6.8 nanoseconds. Gates like this usually take tens of nanoseconds

Speed normally comes at a price. The team found that short, strong pulses trigger multiphoton transitions that had been overlooked, pushing the qubit into unwanted energy levels. Their fix is a pulse shaping method called R2D, which builds on the widely used DRAG technique and cuts those transitions by more than twenty times

The results are striking. Two gates reached fidelities of 99.981 percent and 99.989 percent, and leakage to higher levels stayed below 0.002 percent per gate

There are limits. So far the method has only been tested on a single isolated qubit, so two qubit gates and full processors still need to be tried. The work was part of the QSolid project and is published in Nature Communications as Ultrafast single qubit gates through multi photon transition removal

Faster gates matter because qubits only stay coherent for a limited time. Squeezing more operations into that window helps everything, including error correction. Finding a hidden error source and fixing it is exactly the kind of careful physics the field needs

How much do faster gates help compared with longer coherence times? And will this work carry over to two qubit gates?

Fast but accurate - a new speed record for quantum gateswww.fz-juelich.de