Extended Data Fig. 2: Qubit spectra in the (3, 3) charge configuration region.
From: Operation of a silicon quantum processor unit cell above one kelvin
EDSR spectra of Q1 (lower frequency) and Q2 (upper frequency) as a function of ΔVG = VG1 − VG2, measured using adiabatic microwave pulses with frequency sweep range ΔfAdb = 2 MHz and pulse time τAdb = 0.5 ms, at B0 = 1.4 T and TMC = 40 mK. The cobalt magnet is designed to minimize the magnetic field difference between the two QDs. The bending of the spectrum of Q2 suggests strong mixing with an excited state. Near the (4, 2) region, both spectra split up equally owing to the increase of J coupling. A small splitting can also been seen near the (2, 4) region. At the (2, 4) and (4, 2) electron charge transitions, we no longer have a proper effective two-spin system and the signal vanishes. We operate our qubits mostly near the (2, 4) side (left) for faster EDSR control over Q1.
