Exchange-only CNOT using the SLEDGE quantum dot architecture

Semiconducting quantum dot qubits are a compelling quantum information technology due to their manufacturability, excellent coherence, and high-fidelity SPAM and gate operations.  Exchange-only implementations are of particular interest because they enable qubit control using only asynchronous, baseband voltage pulses.  Two-qubit entangling gates between encoded qubits can also be implemented in an exchange-only context [1, 2], though experimental demonstrations have remained unrealized since such gates involve roughly ten times the number of pulses in single-qubit operations and place strict requirements on device yield and performance.  Here we demonstrate randomized benchmarking and tomography of a two-qubit controlled NOT gate between two exchange-only qubits fabricated using the recently published Single-Layer Etch-Defined Gate Electrode (SLEDGE) architecture [3].  The SLEDGE process can more reliably achieve the device uniformity required for a two-qubit exchange-only gate while maintaining high levels of performance.  Relative to prior two-qubit gate results in silicon qubits, this approach simplifies signal generation and device design [4]. 

 

1 - D. P. DiVincenzo, et al.  Nature 408, 339 (2000).

2 - B. H. Fong, et al.  QIC 11, 1003 (2011).

3 - W. Ha, et al.  arXiv:2107.10916 (2021).

4 - R. W. Andrews et al., Nature Nanotechnol., 14, 747 (2019).