Enabling Leakage Reduction via Fast and High-Fidelity Qutrit Readout

Quantum Error Correction (QEC) is key to operating quantum processors effectively at practical scales. QECs are designed for systems comprising two-level systems, such as qubits, as their fundamental building block. Unfortunately, qubits can leak to third and higher energy levels, making these leaks challenging to detect and mitigate. If not addressed promptly, these leakage errors can proliferate and undermine QEC, leading to significant computational inaccuracies. Here, we present a high-fidelity three-level qubit readout protocol that is simple to implement on dedicated hardware such as FPGAs. Our design enables faster and higher-fidelity leakage detection over approaches using conventional qubit-state discriminators.