Fig. 1: Experimental setup and methods.
From: Amplitude and frequency sensing of microwave fields with a superconducting transmon qudit
a Schematic diagram of the transmon qudit sensor and readout resonator (coplanar waveguide) connected to the employed microwave setup. The gate (PG, ωG) and readout (PM, ωM) pulses are merged with the continuous tone (PF, ωF) which creates the on-chip microwave field to be measured. The combined signals are repeatedly attenuated within the cryostat before reaching the sample mounted at the 25 mK stage. b Graphical representation of the sensor measurement procedure. As the qudit transitions ωi (i = 1, 2) are shifted in the presence of a microwave field, the frequency ωR,i of the corresponding Ramsey oscillations changes, here exemplified for ω1. Ramsey fringes thus reveal the magnitude of these level shifts. Together, the shifts of the first two qudit levels can be used to extract the amplitude and frequency of the microwave field.
