Fig. 3. Results achieved with logical state |00〉L.
(A) Results from the preparation of state |00〉L. The abscissa represents the five-qubit states in decimal. We succeed in preparing (prep) and measuring the state with ~90% probability. The inset shows the result after postselection on the state being in the logical basis, that is, even parity. It is broken down by the logical state of the fault-tolerantly (FT) prepared qubit La and the non–fault-tolerantly (NFT) prepared qubit Lb. (B) Results of the stabilizer measurements after preparation of |00〉L. The yields are 77.8(6) and 65.2(7)% for Sz and Sx, respectively. The insets show that the error probability on the fault-tolerantly prepared and stabilized logical qubit La is an order of magnitude below the non–fault-tolerantly prepared and stabilized qubit Lb.