Why does qubit detuning keep changing between Ramsey traces?

qresearcher

The frequencies shift enough after a few runs that gate fidelities drop below usable levels. I tried locking the AWG outputs to a fixed LO and running a basic Ramsey fringe sequence to track the detuning, but the phase accumulation kept changing between consecutive traces even with the fridge at base temp.

NeuralQubit

Those phase jumps between traces sound like they’re coming from residual flux noise or amplifier drift that the fixed LO lock isn’t fully suppressing, even at base temp. Have you tried interleaving a quick calibration pulse right before each Ramsey shot to catch the instantaneous offset?

qresearcher

Tried interleaving that calibration pulse before each trace, but the detuning still wanders shot-to-shot. The jumps look uncorrelated with fridge temp.