Science 359, 1123–1127 (2018) https://doi.org/10.1126/science.aar4054

Exploiting the electron spin of silicon quantum dots is potentially useful for applications such as quantum information processing. However, such electron spins suffer from extremely small coupling with microwave photons. Now, Samkharadze and co-workers from the Netherlands and Canada have developed an on-chip system that supports strong spin–photon coupling. The idea is that the microwave photon is stored in an on-chip superconducting cavity resonator that is adjacent to a pair of SiGe/Si/SiGe quantum dots. The resonator is square shaped and formed by a thin NbTiN conductor. The impedance of the cavity resonator was about 1 kΩ to enhance the coupling to the quantum dot charge dipole and provide resilience against in-plane magnetic fields. When an electron oscillated between the two dots due to an external magnetic field, it experienced an oscillating transverse magnetic field, yielding indirect spin–charge hybridization that allows strong spin–photon coupling. The observation of vacuum Rabi splitting provided evidence for strong coupling between the spin and the microwave photon. The approach could provide a route to the creation of a large network of quantum-dot-based spin qubit registers.

Credit: AAAS