Effective non-local parity-dependent couplings in qubit chains

Controlled-controlled-phase gates for superconducting qubits mediated by a shared tunable coupler

“…The challenge is, however, to design multi-qubit operations that are fast and accurate when compared to an equivalent two-qubit gate decomposition, to avoid decoherence and reach high fidelities. For superconducting qubit archi-tectures, several techniques for implementing multi-qubit operations have been investigated, e.g., utilizing noncomputational qutrit states to implement more efficient digital decompositions [13,[24][25][26], applying simultaneous pairwise couplings to generate effective multi-qubit interactions [27][28][29][30][31] or introducing a shared coupling element acting as a multi-qubit coupler [32][33][34][35][36]. Each approach comes with its specific advantages and challenges.…”