Second Harmonic Coherent Driving of a Spin Qubit in a Si/SiGe Quantum Dot

TL;DR

This paper demonstrates second harmonic coherent driving of a single electron spin in a Si/SiGe quantum dot, showing potential advantages for quantum computing due to lower microwave requirements and comparable Rabi frequencies.

Contribution

It presents the first experimental demonstration of second harmonic spin driving in a silicon quantum dot, highlighting its feasibility and advantages for quantum information processing.

Findings

Second harmonic Rabi frequency is nearly half of the first harmonic at the same power.

Rabi frequency depends quadratically on the driving amplitude.

Second harmonic driving reduces microwave circuitry complexity.

Abstract

We demonstrate coherent driving of a single electron spin using second harmonic excitation in a Si/SiGe quantum dot. Our estimates suggest that the anharmonic dot confining potential combined with a gradient in the transverse magnetic field dominates the second harmonic response. As expected, the Rabi frequency depends quadratically on the driving amplitude and the periodicity with respect to the phase of the drive is twice that of the fundamental harmonic. The maximum Rabi frequency observed for the second harmonic is just a factor of two lower than that achieved for the first harmonic when driving at the same power. Combined with the lower demands on microwave circuitry when operating at half the qubit frequency, these observations indicate that second harmonic driving can be a useful technique for future quantum computation architectures.