Long-distance coherent coupling of a spin qubit to a superconducting qubit

A coherent link connecting different qubits over long distances is necessary to benefit from the advantages in gating or coherence times of different qubit implementations in a future quantum processor. We realize such a link between a spin qubit and a transmon qubit in a circuit quantum electrodynamics architecture [1] similar to a recent work that involved a charge qubit and a transmon qubit [2]. The spin qubit is a resonant exchange qubit [3] formed by three electrons in a gate defined triple quantum dot in a GaAs/AlGaAs heterostructure. The qubit states are split energetically by exchange interaction. Consequently, the spin qubit can be operated at zero magnetic field and exhibits a decoherence rate of γ₂/2π≈10MHz, limited by hyperfine interaction in the host material. The transmon qubit has γ₂/2π≈0.7MHz limited by Purcell decay. Both qubits are capacitively coupled to a high impedance SQUID array resonator with coupling strengths of g_SQ/2π≈50MHz and g_T/2π≈180MHz for the spin and transmon qubit, respectively. We demonstrate resonant and dispersive interaction between the two qubits mediated by real and virtual microwave photons.

[1] A. J. Landig et al. in preparation
[2] P. Scarlino et al., arXiv : 1806.10039
[3] J. Medford et al., Phys. Rev. Lett. 111, 050501 (2013).