Two-tone electrical drive of spin qubits

Longitudinal coupling of spin qubits to resonators has recently been demonstrated [1]. Theoretically, it had already been proposed as a resource to implement fast two-qubit gates in Si and Ge hole quantum dots [2]. Motivated by recent experiments on Si spin qubits in fin field-effect transistors [3] demonstrating spin qubit operations up to 4 K [4], here we theoretically investigate bimodal electrical microwave driving (transverse and longitudinal) of single spin qubits. The interplay of these drives at differing frequencies gives rise to a wealth of interesting physical phenomena. For instance, the longitudinal modulation induces a gap in the Floquet spectrum of the system, thus making the qubits more robust. We also discuss our findings in light of recent data [5]. Our theoretical description is general and could be applied to both electron and hole quantum dot qubits.