Southwest Quantum Information and Technology

Dynamically Generated Decoherence-Free Subspaces on Superconducting Qubits

Presenting Author: Bibek Pokharel, University of Southern California
Contributing Author(s): Gregory Quiroz, Yifan Sun, Joseph Boen, Lina Tewala, Vinay Tripathi, Matthew Kowalsky, Devon Williams, Jun-Yi Zhang, Paraj Titum, Lian-Ao Wu, Kevin Schultz, Daniel Lidar

Decoherence-free subspaces/noiseless subsystems (DFS/NS) preserve quantum information by identifying subspaces/subsystems of the Hilbert space that remain unaffected by decoherence. Identifying DFS/NS codes under collective decoherence is well-understood, and the resultant codes support scalable and universal quantum computation. While most experimental systems, including superconducting qubit-based devices, do not decohere collectively, it is possible to engineer the conditions for collective decoherence using dynamical decoupling (DD) sequences. We report on the creation and verification of DD-assisted DFS/NS codes on quantum processors provided by the IBM Quantum Experience. We compare the performance of a DFS/NS encoded qubit with its unprotected counterpart. We show that qubit lifetime can be improved substantially using DD-assisted DFS/NS codes. Furthermore, we exploit gate set tomography to characterize logical error channels and estimate logical gate error rates for the DFS/NS encoding. When combined with an analysis of qubit lifetimes for multiple simultaneously encoded qubits, we obtain a comprehensive picture of DFS/NS feasibility and scalability on near-term quantum processors.

(Session 3 : Thursday from 3:30pm-3:50pm)