Bonn 2025 – scientific programme
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QI: Fachverband Quanteninformation
QI 27: Quantum Error Correction
QI 27.4: Talk
Thursday, March 13, 2025, 12:00–12:15, HS VIII
Characterization of errors in a CNOT between surface code patches — •Bálint Domokos1, Áron Márton1, and János K. Asbóth1,2 — 1Budapest University of Technology and Economics — 2HUN-REN Wigner Research Centre for Physics
As current experiments already realize small quantum circuits on error corrected qubits, it is important to fully understand the effect of physical errors on the logical error channels of these fault-tolerant circuits. Here, we investigate a lattice-surgery-based CNOT operation between two surface code patches under phenomenological error models. (i) For two-qubit logical Pauli measurements – the elementary building block of the CNOT – we optimize the number of stabilizer measurement rounds, usually taken equal to d, the size (code distance) of each patch. We find that the optimal number can be greater or smaller than d, depending on the rate of physical and readout errors, and the separation between the code patches. (ii) We fully characterize the two-qubit logical error channel of the lattice-surgery-based CNOT. We find a symmetry of the CNOT protocol, that results in a symmetry of the logical error channel. We also find that correlations between X and Z errors on the logical level are suppressed under minimum weight decoding.
Keywords: Fault-tolerant quantum computation; Surface code; Lattice-surgery