Coherent Coupling of Microwave Photons to Spin and Charge Qubits

January 29th, 2020 KLAUS ENSSLIN ETHZ Zürich

Charge qubits in semiconductors are straightforward to realize using quantum dots, but they suffer from short coherence times. Spin qubits consisting of a single spin (electron) in a quantum dot or two electrons in two quantum dots (singlet-triplet) offer larger coherence times, but are more difficult to manipulate and to couple to superconducting microwave resonators. Using quantum dots in AlGaAs heterostructures we prepare so-called resonant exchange qubits, which consist of three electrons in three quantum dots. The spin configuration in the triple dot systems can be tuned by exchange interactions controlled by a set of gate voltages. This way we demonstrate the strong coupling regime between a spin qubit and a microwave photon. In another configuration one can place a single electron in three tunnel-coupled quantum dots and couple a microwave resonator to the quadrupole moment of the charge configuration rather than the dipole moment. Coupling between superconducting transmons and spin qubits in semiconductors has also been achieved. Other interesting dot, charge and spin configurations can be realized in the well-controlled AlGaAs system thus using qubit systems to probe new physics. Novel 2D material systems such as bilayer graphene and TMDCs offer prospects for other complex charge and spin qubits.

Seminar, January 29, 2020, 12:00. ICFO’s Seminar Room

Hosted by Prof. Adrian Bachtold