Automated Characterization of a Double Quantum Dot using the Hubbard Model

Semiconductor quantum dots are favorable candidates for quantum information processing due to their long coherence time and potential scalability. However, calibration and characterization of an interconnected quantum dot array have proven to be a difficult task. One method to characterize the configuration of such an array is to use the Hubbard model [1]. In this talk, we discuss an automated characterization algorithm that efficiently extracts the Hubbard model parameters including the tunnel coupling and capacitive coupling energy from experimental stability diagrams. Leveraging the dual annealing optimizer, we determine the set of Hubbard parameters that best characterize the experimental data. Our method is advantageous in its robustness in the large tunneling regime when compared to the commonly used DiCarlo method for extracting the tunnel coupling [2]. We extract tunnel couplings ranging from 60 to 470 μeV and discuss the limiting factors of our method, including the stability diagram resolution and parameter degeneracies.

[1] X. Wang, S. Yang, and S. D. Sarma. Quantum theory of the charge-stability diagram of semiconductor double-quantum-dot systems. Physical Review B, 84.115301, 9 2011.

[2] D. Wei, H.-O. Li, G. Cao, G. Luo, Z.-X Zheng, T. Tu, M. Xiao, G.-C. Guo, H.-W. Jiang, and G.-P. Guo. Tuning inter-dot tunnel coupling of an etched graphene double quantum dot by adjacent metal gates. Scientific Reports, 3.3175, 12 2013.