Figure 1

(a) Effective circuit diagram of a transmon. Different from the conventional CPB, the large capacitances $C_s$, $C_g$, and $C_g^{\prime }$ make the transmon work in a regime of significantly increased ratio of $E_J$ and $E_C$. In the regime of $E_J/E_C\gg 1$, the transmon is immune to $1/f$ charge noise, the dominant source of dephasing in other charge qubits. (b) Electrical circuit representation of the two-qubit circuit QED device. The transmons are fabricated at opposite ends of a TLR. Their transition frequencies can be adjusted by external fluxes ${\Phi }_1$ and ${\Phi }_2$ using two local flux bias lines. Input and output signals are coupled to the resonator via two capacitors $C_{\mathrm{in}}$ and $C_{\mathrm{out}}$. Information about the qubit states can be obtained by measuring the amplitude and phase of the cavity transmission.Reuse & Permissions