Here we present the results of an investigation on microwave-induced effects that we have observed in silicon devices, including phosphorous doped and Metal-Oxide-Semiconductor Single Electron Transistors (SET) as well as IDQD. Continuous pulsed microwave and single shot measurements are used to demonstrate that photons in the range of 10-15 GHz allow manipulation of the electron number in the island of a doped SET, despite the high value for the charging energy and in a regime where photon assisted tunnelling is not observable. The method is applied to a device made of a SET with a capacitively coupled IDQD. Partial control of the qubit is obtained and results in the possibility of manipulating charge states in an isolated structure with GHz photons.
Spin qubits in silicon-MOS (SiMOS) quantum dots have recently demonstrated compatibility with existing industry standard CMOS fabrication techniques. These devices have routinely achieved single- and two-qubit gate fidelities above 99% and demonstrated highly entangled two-qubit Bell states in isolated double quantum dot (DQD) unit cells, however coupling between unit cells has remained challenging. In this work, we present a two unit cell, four-qubit SiMOS processor with universal controllability and fully parallelised state initialisation and readout. We use this processor to generate maximally entangled three-qubit states, including the Greenberger-Horne-Zeilinger (GHZ) state, and certify multipartite entanglement through violation of the classical Mermin-witness bound. By using a fully symmetric dynamically decoupled gate sequence to create our entangled states, we are able to preserve the lifetime of the entanglement beyond
T2∗, to a time limited instead by
T2Hahn. These demonstrations pave a road to the scalable operation of larger SiMOS processors, and achieving high purity, long-lived multi-qubit entangled states in them.