Microwave-induced coupling of superconducting qubits

We investigate the quantum dynamics of a system of two coupled superconducting qubits under microwave irradiation. We find that, with the qubits operated at the charge codegeneracy point, the quantum evolution of the system can be described by an effective Hamiltonian which has the form of two coupled qubits with tunable coupling between them. This Hamiltonian can be used for experimental tests on macroscopic entanglement and for implementing quantum gates.

Figure 1

Schematic of the circuit: two capacitively coupled quantronium circuits.

Figure 2

Concurrence for the case $W\gg \delta$. The parameters for this figure are $W=2\pi \times 96.3\mathrm{MHz}$, $\delta =-\Delta =2\pi \times 15.2\mathrm{MHz}$, ${\theta }_{+}\approx 0$, and ${\theta }_{-}=-0.29$.

Figure 3

Parameters $w_1$ and $w_2$ for CNOT ($E_{C1}=605\mathrm{GHz}$, $E_{C2}=454\mathrm{GHz}$, $\delta =-\Delta =-19.2\mathrm{MHz}$, ${\theta }_{+}\approx 0$, ${\theta }_{-}=-0.29$).