Nonlinear Urukul DDS amplitude

cval_

Recent experiments in our lab have led us to characterize the Rabi frequency of our trapped ion qubit as a function of the amplitude that we set on our Urukul 9910 DDS via Artiq. The amplitude is set via the .set() command, and Rabi frequencies are calibrated using simple Rabi flops. The result is:

It seems like there is a highly non-linear response. More characterization found that the amplitude of the DDS output follows a similar response function (measuring the output on a scope as a function of the set amplitude):

What I would have expected is a (somewhat) linear response. Is what we measured normal, is this a bug, or are we using the Urukul improperly?

rjo

Back off the power. Attenuate. Get bigger amplifiers. You are just seeing compression, the amplifier on urukul, your own, aoms are all fundamentally nonlinear. The amplitude you set is just a digital value, it is definitely linear before all non linear components contribute distortion. This is all expected from simple RF basics.

sb10q

There is also an option to bypass the Urukul amplifier with a resistor, if that helps.

cval_

Thank you for both of your replies.

The data I attached was taken using 0.0 dB attenuation. After setting the DDS attenuation to 8 dB, the response does indeed become more linear.

I think I just expected the DDS to be far from a compression point with those parameters.

@sb10q I'll check that out, thanks for the suggestion