Fig. 1: Coupled resonator-qubit system.
From: Strong coupling between a microwave photon and a singlet-triplet qubit
a False colored SEM-image of device A. The NW (green) is divided into two segments by an in-situ grown tunnel barrier (red), thus forming the DQD system. The NW ends are contacted by two Ti/Au contacts (S,D) and the NW segements can be electrically tuned by two Ti/Au sidegates SGR (purple) and SGL (yellow). The voltage anti-node with amplitude Vrf of a high-impedance, half-wave resonator is connected to SGR. Top gates TGL and TGR (orange) are kept at a constant voltage of −0.28 V. The magnetic field is applied in-plane at an angle α with respect to the NW axis, as illustrated by the gray arrow. The white arrows illustrate an even charge configuration with the two degenerate DQD states \({T}_{1,1}^{+}\) and S2,0. b Schematic of the crystal-phase defined DQD. The conduction band of wurzite at energy Ewz and the one of zincblende at energy Ezb are offset by ~100 meV, resulting in a tunnel barrier between the zincblende segments. The intrinsic spin–orbit interaction enables spin-rotating tunneling between these segments. c Energy levels of an even charge configuration as a function of magnetic field B at a fixed positive detuning ε between the dot levels. At finite magnetic fields, \({T}_{1,1}^{+}\) (blue) hybridizes with S2,0 (red) defining a singlet-triplet qubit with an energy splitting given by the spin–orbit interaction strength ΔSO.
