Fast population transfer and entanglement preparation among four superconducting flux qubits

We propose a scheme whereby we optimized the driven pulses applied on qubits to realize fast and robust population of quantum state transfer and entanglement generation between four superconducting flux qubits based on adiabatic passage. The quantum state was transferred from one qubit to another directly with high fidelity through applying an inverted set of pulses. Moreover, the resident time of the quantum state populated on the qubits could be controlled by adjusting the time delay between the driven pulses during the transfer process. Analysis of the dynamics demonstrates that the scheme is insensitive to inhomogeneous qubit–resonator coupling, and even for large detuning regimes of the qubit–resonator interaction, high-fidelity quantum state transfer and entanglement generation can be obtained. Our results also show that the effect of decoherence due to resonator decay and qubit relaxation could be negligible with currently existing technology. (letter)