Robust and Efficient High-Dimensional Quantum State Tomography

The exponential growth in Hilbert space with increasing size of a quantum system means that accurately characterizing the system becomes significantly harder with system dimension d. We show that self-guided tomography is a practical, efficient, and robust technique of measuring higher-dimensional quantum states. The achieved fidelities are over 99.9% for qutrits (d = 3) and ququints (d = 5), and 99.1% for quvigints (d = 20)-the highest values ever realized for qudit pure states. We also show excellent performance for mixed states, achieving average fidelities of 96.5% for qutrits. We demonstrate robustness against experimental sources of noise, both statistical and environmental. The technique is applicable to any higher-dimensional system, from a collection of qubits through to individual qudits, and any physical realization, be it photonic, superconducting, ionic, or spin.

Automated summary

Self-guided tomography is demonstrated to be a practical, efficient, and robust technique for measuring higher-dimensional quantum states with high fidelities. The technique shows excellent performance for both pure and mixed states, achieving record high fidelities. It also exhibits robustness against various sources of experimental noise.