A clever quantum trick brings practical quantum computers closer

A team at ETH Zurich has demonstrated lattice surgery on superconducting logical qubits. The method splits a single protected qubit into two entangled logical qubits while error correction remains active. The experiment was led The logical qubit was encoded in seventeen physical qubits forming a square pattern. Stabilizer measurements occurred every 1.66 microseconds to correct bit flips and phase flips. Measuring three data qubits in the center divided the code into two halves and created the entanglement. Bit flip correction continued through the splitting process. The operation can be combined with merging steps to implement a controlled-NOT gate. Forty one physical qubits would be required to stabilize the split against phase flips as well. The result represents an advance in fault tolerant quantum computing with superconducting hardware. It is the first performance of lattice surgery on this type of qubit. The study appears in Nature Physics.