Parametrically activated two-qubit interactions in a superconducting qubit system for quantum simulations

A current bottleneck for quantum computation and simulation is the realization of flexible high-fidelity two-qubit operations. Gates based on parametrically driven tunable couplers offer a convenient method to entangle qubits by selectively activating different interaction terms in the effective Hamiltonian. Here, we present experimental results on a system comprising fixed-frequency superconducting transmons capacitively coupled to a tunable coupler realized in our setup by a flux-tunable qubit. The two-qubit interactions are activated via a parametric frequency modulation. We realize different types of interactions with fidelities up to 97% by adjusting the frequency and phase of this modulation. Our experimental findings are backed by analytical calculations and numerical simulations, revealing that the fidelities of these two qubit operations are currently limited by the coherence of the tunable coupler. Eventually, using such a set of single and two qubit interactions, analog simulations of quantum systems such as molecules or spin systems could be realized.