3:30–4:30 pm
Maria Goeppert-Mayer Lecture Hall Kersten Physics Teaching Center
Room 106
5720 S. Ellis Avenue
Realizing Fault-Tolerant Superconducting Quantum Processors
Andreas Wallraff, ETH Zurich
Host: David Schuster
Superconducting circuits are a prime contender both for addressing noisy intermediate-scale quantum (NISQ) problems and for realizing universal quantum computation in fault-tolerant processors. Superconducting circuits also play an important role in state of the art quantum optics experiments at microwave frequencies and provide interfaces in hybrid systems when combined with semiconductor quantum dots, color centers or mechanical oscillators. In this talk, I will discuss our experimental efforts towards realizing quantum error correction in superconducting circuits, which is an essential ingredient for reaching the full potential of fault-tolerant universal quantum computation. We pursue an approach based on the surface code in which we redundantly encode a logical qubit into a set of physical qubits. Using seven superconducting qubits, we have experimentally implemented the smallest viable instance of such a surface code, capable of repeatedly detecting any single error. We perform our experiments in a multiplexed device architecture [1], which enables fast, high fidelity, single-shot qubit readout [2], unconditional reset [3], and high fidelity single and two- qubit gates. Using ancilla-based stabilizer measurements, we initialize the cardinal states of the encoded logical qubit with high fidelity. We then repeatedly check for errors using the stabilizer readout and observe that the logical quantum state is preserved with a lifetime and coherence time longer than those of any of the constituent qubits, when no errors are detected [4]. Thus, we demonstrate an enhancement of the conditioned logical qubit coherence times beyond the coherences of its best constituent physical qubits. We are extending our current device architecture to a 17 qubit surface code, capable of not only detecting errors but also correcting errors using real-time feedback as demonstrated in our recent entanglement stabilization experiment [5].
References
[1] J. Heinsoo et al., Phys. Rev. Applied 10, 034040 (2018)
[2] T. Walter et al., Phys. Rev. Applied 7, 054020 (2017)
[3] P. Magnard et al., Phys. Rev. Lett. 121, 060502 (2018)
[4] C. Kraglund Andersen et al., arXiv:1912.09410 (2019)
[5] C. Kraglund Andersen et al., npj Quantum Information 5, 69 (2019)