Fault-tolerant operation of a logical qubit in a diamond quantum processor

Area of Science:

• Quantum Information Science
• Solid-State Physics
• Quantum Computing

Background:

• Solid-state spin qubits show promise for quantum computation and networks.
• Previous work established multi-qubit control and non-fault-tolerant error correction.
• Large-scale quantum systems necessitate fault-tolerant logical qubits to overcome operational noise.

Purpose of the Study:

• To demonstrate fault-tolerant operations on a logical qubit using spin qubits in diamond.
• To implement a novel encoding protocol and fault-tolerant Clifford gates.
• To showcase flagged stabilizer measurements for quantum error correction.

Main Methods:

• Utilized the five-qubit code with a seven-qubit flag protocol for fault tolerance.
• Employed a new encoding protocol based on repeated multi-qubit measurements.
• Performed fault-tolerant manipulation via single-qubit Clifford gates and real-time flagged stabilizer measurements.

Main Results:

• Demonstrated fault-tolerant operations on a logical qubit in a solid-state platform.
• The new encoding protocol outperformed non-fault-tolerant schemes.
• Successfully executed flagged stabilizer measurements with real-time processing.

Conclusions:

• This work represents a key step towards fault-tolerant quantum information processing using solid-state spins.
• The demonstrated fault-tolerant protocols on the logical-qubit level are essential for future quantum computers.
• Further improvements in fidelity and qubit count are needed for logical error rates below physical error rates.