All-Microwave Leakage Reduction Units for Quantum Error Correction with Superconducting Transmon Qubits
Jorge Marques, Hany Ali, B. M. Varbanov, Matvey Finkel, H. M. Veen, S. L. M. van der Meer, S. Vallés-Sanclemente, Nandini Muthusubramanian, Marc Beekman, Nadia Haider, Barbara M. Terhal, L. DiCarlo
Abstract
Minimizing leakage from computational states is a challenge when using many-level systems like superconducting quantum circuits as qubits. We realize and extend the quantum-hardware-efficient, all-microwave leakage reduction unit (LRU) for transmons in a circuit QED architecture proposed by Battistel et al. This LRU effectively reduces leakage in the second- and third-excited transmon states with up to 99% efficacy in 220 ns, with minimum impact on the qubit subspace. As a first application in the context of quantum error correction, we show how multiple simultaneous LRUs can reduce the error detection rate and suppress leakage buildup within 1% in data and ancilla qubits over 50 cycles of a weight-2 stabilizer measurement.