Fig. 2: Calibration and characterization of three-qubit gate CCPhase and CSWAP phase. | npj Quantum Information

Fig. 2: Calibration and characterization of three-qubit gate CCPhase and CSWAP phase.

From: Extensive characterization and implementation of a family of three-qubit gates at the coherence limit

Fig. 2

a Calibration and verification of γ (or equivalently δ) similar to typical CZ calibration39. We use \(\left\vert 1+0\right\rangle\) and \(\left\vert 1+1\right\rangle\) as probe states, as they are insensitive to the currently unknown SWAP phase, ϕ0, and oscillate γ + π out of phase of one another. b Performing a cross-Ramsey experiment using Q1 prepared in \(\left\vert +\right\rangle\) and using the three-qubit gate to SWAP the population to Q2. We define ϕ = 0 from the phase that maximizes the expectation value in I ⊗ I ⊗ X. We additionally demonstrate full SWAP-phase control regardless of input state after calibration of γ = 0.

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