Demonstration of Fidelity Improvement Using Dynamical Decoupling with Superconducting Qubits

Bibek Pokharel; Namit Anand; Benjamin Fortman; Daniel A Lidar

doi:10.1103/PhysRevLett.121.220502

Demonstration of Fidelity Improvement Using Dynamical Decoupling with Superconducting Qubits

Phys Rev Lett. 2018 Nov 30;121(22):220502. doi: 10.1103/PhysRevLett.121.220502.

Authors

Bibek Pokharel¹, Namit Anand², Benjamin Fortman³, Daniel A Lidar^{1

2

3

4}

Affiliations

¹ Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089, USA.
² Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA.
³ Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
⁴ Center for Quantum Information Science & Technology, University of Southern California, Los Angeles, California 90089, USA.

PMID: 30547654
DOI: 10.1103/PhysRevLett.121.220502

Abstract

Quantum computers must be able to function in the presence of decoherence. The simplest strategy for decoherence reduction is dynamical decoupling (DD), which requires no encoding overhead and works by converting quantum gates into decoupling pulses. Here, using the IBM and Rigetti platforms, we demonstrate that the DD method is suitable for implementation in today's relatively noisy and small-scale cloud-based quantum computers. Using DD, we achieve substantial fidelity gains relative to unprotected, free evolution of individual superconducting transmon qubits. To a lesser degree, DD is also capable of protecting entangled two-qubit states. We show that dephasing and spontaneous emission errors are dominant in these systems, and that different DD sequences are capable of mitigating both effects. Unlike previous work demonstrating the use of quantum error correcting codes on the same platforms, we make no use of postselection and hence report unconditional fidelity improvements against natural decoherence.