Tutorial: qubit calibration

Tune up a qubit with Presto

Performing all the standard qubit measurements is a good place to start learning how to program the Presto API. In this tutorial, we begin with a simple resonator spectroscopy using lockin mode, and we continue with all the standard pulsed measurements using pulsed mode. You can view the complete source code of the example scripts in the presto-measure repository. We recommend you read the examples in order as later measurements build on previous ones. If you want to skip ahead, be sure to have a look at the first scripts using each of the lockin and pulsed mode: Resonator spectroscopy and Rabi amplitude.

Here’s a list of the examples in this tutorial with a brief description, click on the headers to view the related page. These measurements, and a few more, are also published in the Presto paper.

Resonator spectroscopy

lockin – Simple single-frequency sweep of the resonator in continuous wave.

Power sweep of resonator

lockin – 2D sweep of drive amplitude and frequency of the resonator.

Frequency and DC bias sweep of flux tunable resonator

lockin – 2D sweep of DC bias and frequency of the flux tunable resonator.

Two-tone spectroscopy of the qubit

lockin – Two-tone spectroscopy: 2D sweep of qubit drive amplitude and frequency, with fixed resonator drive frequency and amplitude.

Rabi in amplitude

pulsed – Rabi oscillations by driving the qubit with a pulse of variable amplitude and constant duration. Multiple pulses can be applied to increase the accuracy of fitted results.

Rabi time

pulsed – 2D sweep where we measure Rabi oscillations by driving the qubit with a square pulse of variable duration and variable amplitude. Fit the amplitude-dependent Rabi rate.

Relaxation time \(T_1\)

pulsed – Measure the energy-relaxation time \(T_1\).

Ramsey \(T_2^*\)

pulsed – Measure Ramsey oscillations by changing the delay between two \(\pi/2\) pulses. Fit detuning of control frequency from qubit, and the coherence time \(T_2^*\).

Hahn echo \(T_2\)

pulsed – Measure the decoherence time \(T_2\) with a Ramsey-echo experiment.

Ramsey fringes

pulsed – Measure Ramsey fringes by changing the delay between two \(\pi/2\) pulses and their detuning from the qubit frequency.

Resonator sweep with the qubit in the excited state

pulsed – Pulsed frequency sweep of the resonator with and without a \(\pi\) pulse: plot and fit resonance curves for ground and excited states, and find the optimal readout frequency.

Pulsed two-tone spectroscopy

pulsed – Two-tone spectroscopy: 1D sweep of qubit drive frequency, with fixed amplitude and fixed resonator drive frequency and amplitude.