Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot-Paris 7 et CNRS, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France.
Phys Rev Lett. 2011 Nov 4;107(19):190402. doi: 10.1103/PhysRevLett.107.190402. Epub 2011 Nov 2.
We investigate theoretically the dynamical behavior of a qubit obtained with the two ground eigenstates of an ultrastrong coupling circuit-QED system consisting of a finite number of Josephson fluxonium atoms inductively coupled to a transmission line resonator. We show a universal set of quantum gates by using multiple transmission line resonators (each resonator represents a single qubit). We discuss the intrinsic "anisotropic" nature of noise sources for fluxonium artificial atoms. Through a master equation treatment with colored noise and many-level dynamics, we prove that, for a general class of anisotropic noise sources, the coherence time of the qubit and the fidelity of the quantum operations can be dramatically improved in an optimal regime of ultrastrong coupling, where the ground state is an entangled photonic "cat" state.
我们从理论上研究了由有限数目的约瑟夫森磁通量子原子感应耦合到传输线谐振器组成的超强耦合电路-QED 系统的两个基态本征态获得的量子位的动力学行为。我们通过使用多个传输线谐振器（每个谐振器代表一个单量子位）展示了一组通用的量子门。我们讨论了磁通量子人工原子噪声源的固有“各向异性”性质。通过带有有色噪声和多能级动力学的主方程处理，我们证明，对于一类各向异性噪声源，在基态为纠缠光子“猫”态的超强耦合的最优条件下，量子位的相干时间和量子操作的保真度可以显著提高。
