Repeated multi-qubit readout and feedback with a mixed-species trapped-ion register

Area of Science:

• Quantum Information Science
• Atomic Physics
• Quantum Computing

Background:

• Quantum error correction is vital for scalable quantum computing.
• Experimental realization requires repetitive error detection and correction.
• Trapped-ion systems face challenges with crosstalk and heating during qubit readout.

Purpose of the Study:

• To demonstrate sequential quantum error detection and correction in a trapped-ion system.
• To stabilize two-qubit subspaces and Bell states using feedback control.
• To develop methods for scalable trapped-ion quantum computing and metrology.

Main Methods:

• Utilized a mixed-species trapped-ion system with beryllium microwave qubits and a calcium optical qubit.
• Performed up to 50 sequential measurements of qubit correlations.
• Implemented multi-qubit mixed-species gates for information transfer and sympathetic cooling for heating mitigation.

Main Results:

• Achieved sequential measurements of qubit correlations with negligible crosstalk.
• Successfully stabilized two-qubit subspaces and Bell states.
• Demonstrated sympathetic cooling to mitigate heating during detection.

Conclusions:

• The developed methods are essential for scaling trapped-ion quantum computing.
• The techniques advance quantum-state control and entanglement-enhanced quantum metrology.
• This work provides a pathway for robust quantum information processing.