We propose a model to implement the standard two-qubit quantum phase gate via a large detuned interaction of two superconducting quantum interference devices(SQUIDs) with a single-mode vacuum cavity-field.With the constructed phase gate,a scheme for generating an N-qubit cluster state is also presented.In our protocol,the quantum information is encoded in the ground states of two rf SQUIDs.During the interaction between the rf SQUIDs and the single-mode vacuum cavity-field,the effect of decoherence caused from the upper levels of the SQUID system is negligible due to fact that the excited states of the rf SQUIDs are adiabatically eliminated under large detuning condition.The experimental feasibility of the schemes is also discussed.
We proposed an efficient scheme for constructing a quantum controlled phase-shift gate and generating the cluster states with rf superconducting quantum interference devices (SQUIDs) coupled to a microwave cavity through adiabatic evolution of dark eigenstates. During the operation, the spontaneous emission is suppressed since the rf SQUIDs are always in the three lowest flux states. Considering the influence from the cavity decay with achievable experimental parameters, we numerically analyze the success probability and the fidelity for generating the two-SQUID maximally entangled state and the controlled phase-shift gate by adiabatic passage.
We present a way to realize an
n-qubit controlled phase gate with superconducting quantum-interference devices (SQUIDs) by coupling them to a superconducting resonator. In this proposal, the two logical states of a qubit are represented by the two lowest levels of a SQUID. An intermediate level of each SQUID is utilized to facilitate coherent control and manipulation of quantum states of the qubits. It is interesting to note that an
n-qubit controlled phase gate can be achieved with
n SQUIDs by successively applying a $\ensuremath{\pi}∕2$ Jaynes-Cummings pulse to each of the $n\ensuremath{-}1$ control SQUIDs before and after a $\ensuremath{\pi}$ Jaynes-Cummings pulse on the target SQUID.