The Research On The Effects Of Several Thermal Reservoir Environments To The Superconducting Qubit Quantum Correlations

With the development of the quantum computing and quantum communicationtechnology, superconducting qubits shows enormous potential in quantum informationtechnology. Because of the solid-state qubits can be integrated, it becomes one of themost potential components in realizing the quantum computers. Due to the strongdissipation of the environment to the qubit, in the quantum control process, the qubitinteraction with the environment or other reasons, will lead to the disappearance ofthe quantum coherence, the quantum information will lost in the uncontrolledenvironment, and the decoherence phenomenon appearance. The quantum correlationis considered to an essential method to study the quantum information process, to thisend, we have studied the interaction between the coupled qubits and the system, andanalyzed the effect of the interaction to the concurrence and the quantum discord.1. Based on the classic circuit theory and the Bloch-Redfield function, studiedthe dynamical evolution of the superconducting flux qubit circuit. Under two-levelapproximation, we analyzed the effects of Ohm, sub-Ohm and super-Ohm thermalreservoir environment to the superconducting flux qubit decoherence. The resultsshow:(1) Under the super-Ohm thermal reservoir environment, improve theenvironmental indicators coefficient can help to extend the decoherence time of thesuperconducting flux qubits, thus improving the magnetic flux qubits decoherence.(2) In comparison, when the other conditions remain unchanged, building a sub-Ohmthermal reservoir environment or a super-Ohm thermal reservoir environment is moreconductive to improve the decoherence.(3) Under the super-Ohm thermal reservoirenvironment, improve the environmental indicators coefficient can help to extendthe decoherence time of the superconducting flux qubits, thus improving themagnetic flux qubits decoherence. Under certain conditions, we can optimize thecircuit design, making use of the coupling effects between the inductor coils, reducethe system’s decoherence, but this requires further detailed study.2. Under dissipation model in different environments, we gave the dynamicalevolution of the coupled qubit quantum correlations, compared and studied the change characteristics between the concurrence and the quantum discord. We found that theconcurrence is strongly dependent on the initial environment, and the entanglementdeath phenomenon occurs in the evolution process inevitable. Under certain initialconditions, the dark and bright periods will appear in the evolution of entanglement,but finally, the concurrence will still be equal to zero. Due to the decoherence effects,although the quantum discord will eventually reduce to zero, But unlike theentanglement evolution, the quantum discord generally does not occur entanglementsudden death phenomenon, and the quantum discord survives longer, and doesn’tappear entangled death, that is to say the use of quantum discord is more conductiveto dealing with the quantum information.