So far we have seen the single qubit gates and their representation on the Bloch sphere, but how can we actually implement them on a spin qubit? That is done by applying a microwave signal electrically. Fabio guides us through the requirements of this microwave pulse and shows how accurate those need to be to perform a single qubit gate. He also gives us an overview of how to apply it to a many-qubit system using today’s technology.

• The microwave pulse to perform a single qubit gate on a spin qubit needs to have a frequency matching the qubit Larmor frequency, with the phase that determines the axis of rotation. And the angle of rotation is determined by the amplitude and duration of the pulse.
• To know the accuracy of those parameters one can set a targeted infidelity of the qubit rotation.
• In a n-qubit system we need to tune the microwave drive for each of these qubits to the frequency of the specific qubit; then we can sum them up and send them through the same coaxial cable.
• To do so, we will sum up the qubit signal in the digital domain, send it to a DAC and then multiply a single signal by our microwave oscillator and send it to the coaxial cable.