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)


SQuInT Chief Organizer
Akimasa Miyake, Associate Professor

SQuInT Co-Organizer
Brian Smith, Associate Professor

SQuInT Local Organizers
Philip Blocher, Postdoc
Pablo Poggi, Research Assistant Professor
Tzula Propp, Postdoc
Jun Takahashi, Postdoc
Cunlu Zhou, Postdoc

SQuInT Founder
Ivan Deutsch, Regents' Professor, CQuIC Director

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