In a general aspect, a quantum control device includes a substrate having a substrate surface. An insulator layer is disposed over the substrate surface and defines a cavity. The insulator layer includes an insulator surface that defines an opening to the cavity. The quantum control device also includes a field-responsive layer over the insulator surface. The field-responsive layer includes a target region that resides over the opening to the cavity. The quantum control device additionally includes a projection extending from the substrate into the cavity and terminating at a tip. The projection is configured to produce an electric field that interacts with a quantum state in the target region. The tip resides in the cavity and configured to concentrate the electric field produced by the projection.

An electronic device including: a semiconductor nanowire; at least two separate first control gates, arranged next to each other on the side of a first lateral surface of the nanowire, and configured to each control the electrostatic potential of a quantum dot intended to be formed in the nanowire; at least one second control gate arranged on the side of a second lateral surface, opposite to the first lateral surface, of the nanowire, and configured to control the electrostatic potential of a coupling region intended to be formed between two quantum dots; wherein all the first control gates are arranged on the side of the first lateral surface only, and the or all the second control gates are arranged on the side of the second lateral surface only.