Coherent spectroscopy of a Si/SiGe double quantum dot molecule

We report the wideband microwave spectroscopy of a gate-defined double quantum dot qubit. The double quantum dot, operated with a total of five electrons, has a series of molecular energy levels that can be manipulated coherently. Working in the (4,1)-(3,2) charge configuration, we use a two-step Ramsey pulse sequence to characterize the energy levels of the (3,2) charge configuration as a function of the double-dot detuning. Using this procedure, we demonstrate differences in the dispersion for two closely spaced levels (<2GHz separation in energy). We present measurements of the broadband spectrum, discovering seven energy levels that can be addressed coherently, each with distinct Rabi oscillation characteristics. The double quantum dot is formed in an undoped Si/SiGe heterostructure using an overlapping gate architecture [1]. The measurements are acquired using a tunable latched measurement scheme similar to that in Ref. [2], made possible by the presence of independent reservoirs and corresponding tunnel barriers for each quantum dot.

[1] Zajac, D. et al., Appl. Phys. Lett. 106, 223507 (2015)
[2] S. A. Studenikin et al. Appl. Phys. Let., 101, 23 (2012)