Gate-set evaluation metrics for closed-loop optimal control on nitrogen-vacancy center ensembles in diamond

Area of Science:

• Quantum science and technology
• Quantum information processing
• Quantum computing hardware

Background:

• Precise control of quantum dynamics is crucial for quantum operations (quantum gates).
• Quantum gates are susceptible to application-specific errors, impacting control strategies.
• Contextual gate-set performance measures are needed for application-oriented quantum optimal control.

Purpose of the Study:

• To compare the efficacy of different measures for closed-loop quantum optimal control.
• To identify trade-offs between quantum process tomography, gate-set tomography (GST), and randomized benchmarking (RB).
• To demonstrate enhancement of gate-set performance using optimal control.

Main Methods:

• Utilized a macroscopic ensemble of nitrogen-vacancy (NV) centers in diamond as an experimental test-bed.
• Explored and compared quantum process tomography (QPT), linear inversion gate-set tomography (LIGST), randomized linear gate-set tomography (RLIGST), and randomized benchmarking (RB).
• Applied closed-loop quantum optimal control strategies informed by these performance measures.

Main Results:

• Demonstrated the relative trade-offs and applicability of QPT, LIGST, RLIGST, and RB in optimal control experiments.
• Significantly enhanced the performance of the investigated quantum gate-set.
• Achieved measurable improvements across all evaluated gate-set performance measures.

Conclusions:

• The choice of gate performance measure significantly impacts the success of quantum optimal control.
• Optimized control strategies based on appropriate measures can lead to substantial improvements in quantum gate fidelity.
• NV centers in diamond provide a viable platform for testing and advancing quantum control techniques.