Large coupling in a silicon quantum dot array*

Gate-defined silicon quantum dots have been successfully used to encode two-qubit devices [1]. Central to attaining this multi-qubit control is the method used for inter-qubit coupling, where qubits may be coupled through capacitive or tunneling (exchange) interactions. Previous works have studied the capacitive coupling between two adjacent double quantum dots (DQDs) in accumulation-mode, overlapping gate architectures in SiGe [2,3] and have achieved capacitive couplings on the order of 20-50 GHz. In this talk, we examine the charge dynamics between two DQDs in a similar depletion-mode SiGe device we have fabricated. This device contains a linear array of four coupled QDs, and we study the inter-dot coupling’s transition from 45 GHz to measurements exceeding 200 GHz. We explore the mechanism responsible for the observed trend in inter-dot coupling as the barrier separating the two DQDs is decreased and remark on the device’s ability to reach such large couplings.

1]         M. Veldhorst, C. H. Yang, J. C. C. Hwang, W. Huang, J. P. Dehollain, J. T. Muhonen, S. Simmons, A. Laucht, F. E. Hudson, K. M. Itoh, A. Morello, and A. S. Dzurak, A Two-Qubit Logic Gate in Silicon, Nature 526, 410 (2015).

[2]       S. F. Neyens, E. R. MacQuarrie, J. P. Dodson, J. Corrigan, N. Holman, B. Thorgrimsson, M. Palma, T. McJunkin, L. F. Edge, M. Friesen, S. N. Coppersmith, and M. A. Eriksson, Measurements of Capacitive Coupling Within a Quadruple-Quantum-Dot Array, Physical Review Applied 12, (2019).

[3]       D. M. Zajac, T. M. Hazard, X. Mi, E. Nielsen, and J. R. Petta, Scalable Gate Architecture for a One-Dimensional Array of Semiconductor Spin Qubits, Physical Review Applied 6, (2016).