Logical qubits become entangled on IBM's Phoenix processor
Different experiments probe the ingredients needed for encoded quantum operations.
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Researchers report entangling encoded on IBM's Phoenix superconducting processor using lattice surgery, a method for joining and separating error-correcting code patches. Their October 23 preprint describes logical Bell-state fidelities above 93 percent.[1]
The device contains 120 . By excluding underperforming components and using noise-informed decoding, the team reports distance-three and distance-five surface codes with logical error below 1 percent per correction round.[1]
With three logical qubits, it also demonstrates teleportation of selected states and gates, reporting fidelities between 78 and 93 percent.[1]
These measures describe different tasks and should stay separate. The physical processor's 120 qubits do not represent 120 logical qubits, and a memory error per round is not the same quantity as the fidelity of a logical operation.[1]
The study provides experimental evidence for several ingredients of encoded computation. It does not establish that a complete, application-scale fault-tolerant machine has been built.[1]