Demonstration of Fidelity Improvement Using Dynamical Decoupling with Superconducting Qubits

Area of Science:

• Quantum Information Science
• Quantum Computing Hardware
• Quantum Error Mitigation

Background:

• Quantum computers are susceptible to decoherence, limiting their performance.
• Dynamical decoupling (DD) is a simple strategy to reduce decoherence without encoding overhead.
• Previous studies have explored quantum error correction, often requiring postselection.

Purpose of the Study:

• To assess the suitability of dynamical decoupling (DD) on current cloud-based quantum computers.
• To demonstrate fidelity improvements for individual and entangled qubits using DD.
• To identify dominant error sources and evaluate DD's mitigation capabilities.

Main Methods:

• Implementation of DD sequences on superconducting transmon qubits using IBM and Rigetti quantum platforms.
• Comparison of DD-protected qubit evolution against unprotected free evolution.
• Analysis of error types, including dephasing and spontaneous emission.

Main Results:

• Substantial fidelity gains were achieved for individual superconducting transmon qubits using DD.
• DD provided a lesser degree of protection for entangled two-qubit states.
• Dephasing and spontaneous emission were identified as dominant error sources, both mitigated by DD sequences.

Conclusions:

• Dynamical decoupling is a viable and effective method for error mitigation in current noisy, small-scale quantum computers.
• DD offers unconditional fidelity improvements against natural decoherence, without requiring postselection.
• The findings support the practical application of DD for enhancing the performance of cloud quantum computing platforms.