Collective preparation of large quantum registers with high fidelity

We report on the preparation of a large quantum register of 5612 qubits, with the unprecedented high global fidelity of F ≃ 0.9956 . This was achieved by applying an improved cooperative quantum information erasure protocol (Buffoni and Campisi 2023 Quantum 7 961) to a programmable network of superconducting qubits featuring a high connectivity. At variance with the standard method based on the individual reset of each qubit in parallel, here the quantum register is treated as a whole, thus avoiding the well-known orthogonality catastrophe whereby even an extremely high individual reset fidelity f results in vanishing global fidelities F = f N with growing number N of qubits.