All-microwave CNOT gate between two transmon qubits

We have embedded two fixed frequency Al/AlO_x/Al transmon devices, with qubit transition frequencies at 6.07 GHz and 6.75 GHz, in a single 3D Al cavity with a fundamental mode at 7.60 GHz. Strong coupling between the cavity and the qubits results in an effective qubit-qubit coupling of the form (σ₁⁺σ₂^- + σ₁^-σ₂⁺) with a coupling strength of 26 MHz resulting in a qubit resonance shift of 1 MHz depending on the state of the other qubit. Using an all-microwave technique, we demonstrate the operation of an entangling CNOT gate between the two qubits, with a gate time of 900 ns. The final fidelity for the gate is approximately 90% which is verified by performing quantum state tomography on the two qubits. Improvements to the fidelity of the gate will be discussed.