Quantum-control approach to realizing a Toffoli gate in circuit QED
Vladimir M. Stojanović, Arkady Fedorov, Andreas J. Wallraff, Christoph Bruder · Physical Review B · 2012
We study the realization of a Toffoli gate with superconducting qubits in a circuit-quantum-electrodynamics setup using quantum-control methods. Starting with optimized piecewise-constant control fields acting on all qubits and typical strengths of $XY$-type coupling between the qubits, we demonstrate that the optimal gate fidelities are affected only slightly by a ``low-pass'' filtering of these fields with the typical cutoff frequencies of microwave driving. Restricting ourselves to the range of control-field amplitudes for which the leakage to the noncomputational states of a physical qubit is heavily suppressed, we theoretically predict that in the absence of decoherence and leakage, within 75 ns a Toffoli gate can be realized with intrinsic fidelities higher than $90%$ while fidelities above $99%$ can be reached in about 140 ns.