Dynamically generated decoherence-free subspaces and subsystems on superconducting qubits.

Area of Science:

• Quantum Information Science
• Quantum Computing
• Quantum Error Correction

Background:

• Decoherence-free subspaces and subsystems (DFS) protect quantum information by encoding it into symmetry-protected states resistant to environmental noise.
• Experimental systems may lack inherent DFS, necessitating methods to induce them.
• Dynamical decoupling (DD) is a technique used to mitigate decoherence by applying sequences of control pulses.

Purpose of the Study:

• To experimentally demonstrate dynamical decoupling-generated decoherence-free subsystem logical qubits for the first time.
• To investigate the performance of DFS codes in preserving quantum information on superconducting quantum processors.
• To assess the fidelity improvement offered by DFS logical qubits compared to physical qubits under DD.

Main Methods:

• Utilized IBM Quantum superconducting processors to implement two and three-qubit DFS codes.
• Employed dynamical decoupling (DD) techniques to engineer symmetries supporting DFS.
• Combined DD with error detection mechanisms to evaluate the performance of DFS logical qubits.

Main Results:

• Achieved up to a 23% improvement in state preservation fidelity for DFS logical qubits over physical qubits subjected to DD alone.
• Demonstrated beyond-breakeven fidelity improvement for DFS-encoded qubits, signifying a significant advancement.
• Investigated DFS codes comprising up to six and seven noninteracting logical qubits.

Conclusions:

• Dynamical decoupling can be effectively used to generate decoherence-free subsystems for quantum information encoding.
• DFS codes offer a promising pathway toward enhanced computational accuracy in quantum processors.
• The experimental demonstration validates the potential utility of DFS codes for robust quantum computation.