IQIM Postdoctoral and Graduate Student Seminar

Note: This is a special IQIM seminar, Wednesday at 4 pm.

Abstract: Magic state cultivation is a state-of-the-art method to prepare high-fidelity non-Clifford resource states for universal quantum computation with low spacetime overhead. We present an efficient cultivation protocol in the surface code that achieves lower spacetime overhead than all existing schemes, reaching a logical error rate of 1e-9 with a physical error rate of 0.1% using an average of 9 cultivation attempts until success. Our improvements arise from three primary design choices: (1) measuring the fold-transversal Hadamard of the unrotated surface code in a qubit-efficient way, (2) leveraging compact unitary circuits for code conversion within the surface code family, and (3) employing a two-step procedure to expand to a larger final code without substantial qubit overhead. Further, we exactly simulate the end-to-end cultivation protocol using a "handoff" technique, which transfers the output of statevector simulations on a few qubits to stabilizer simulations on hundreds of qubits. Our proposal is well suited to practical implementation in architectures with nonlocal connectivity.