This paper proposes a scheme to enhance the fidelity of symmetric and asymmetric quantum cloning using a hybrid system based on nitrogen-vacancy (N-V) centers. By setting different initial states, the present scheme can implement optimal symmetric (asymmetric) universal (phase-covariant) quantum cloning, so that the copies with the assistance of a Current-biased Josephson junction (CBJJ) qubit and four transmission-line resonators (TLRs) can be obtained. The scheme consists of two stages: the first stage is the implementation of the conventional controlled-phase gate, and the second is the realization of different quantum cloning machines (QCM) by choosing a suitable evolution time. The results show that the probability of success for QCM of a copy of the equatorial state can reach 1. Furthermore, the | W 4 ± ⟩ entangled state can be generated in the process of the phase-covariant quantum anti-cloning. Finally, the decoherence effects caused by the N-V center qubits and CBJJ qubit are discussed.
We demonstrate a scheme for realizing quantum-information storage (retrieval) into (from) a quantum memory using a hybrid quantum system, which consists of
N nitrogen-vacancy (N-
V) centers (as memory),
N transmission line resonators (TLRs) (as data bus), and
N current-biased Josephson-junction (CBJJ) superconducting phase qubits (as heads of read and write). By virtually exciting the vibrational modes of the TLRs, this can produce an effective coupling between the N-
V centers and the CBJJs in the system. Because the operation time ($\ensuremath{\sim}{10}^{\ensuremath{-}8}$ s) is much shorter than the decoherence time of the CBJJ ($\ensuremath{\sim}{10}^{\ensuremath{-}5}$ s), the quantum information can be transferred between the N-
V centers and the CBJJs easily. Owing to the strong-coupling condition $[\ensuremath{\lambda}/2\ensuremath{\pi}\ensuremath{\gg}({\ensuremath{\gamma}}_{eg},\ensuremath{\Gamma},{\ensuremath{\gamma}}_{\ensuremath{\phi}})]$ and the long coherence time ($\ensuremath{\sim}{10}^{\ensuremath{-}3}$ s) of the N-
V centers, the quantum information can be stored in the memory steadily, and it can be retrieved with a high fidelity (
>96). This scheme provides a scalable way of exchanging quantum information between different quantum interfaces, and has the experimental feasibility with currently available experimental technology.
We study a hybrid quantum computing system using a nitrogen-vacancy center ensemble (NVE) as quantum memory, a current-biased Josephson junction (CBJJ) superconducting qubit fabricated in a transmission line resonator (TLR) as the quantum computing processor, and the microwave photons in TLR as the quantum data bus. The storage process is seriously treated by considering all kinds of decoherence mechanisms. Such a hybrid quantum device can also be used to create multiqubit
W states of NVEs through a common CBJJ. The experimental feasibility is achieved using currently available technology.
We proposed an efficient scheme for implementing the large-scale one-way Quantum computing (QC) with a novel hybrid solid-state quantum system. This system consists of N Nitrogen-vacancy (N-V) centers coupled to N separate Transmission line resonators (TLRs), which are interconnected by a Current-biased Josephson junction (CBJJ) superconducting phase qubit. We showed the way of preparation of N-qubit linear cluster state with N N-V centers, then we demonstrated the way of extending cluster state by connecting two pieces of linear cluster states into two-dimensional cluster state, last, with our designed new structures, we demonstrated the QC basic operations. It means that our scheme may open up promising possibilities for implementing the practical and scalable one-way quantum computers with the hybrid solid-state quantum system. We discussed the experimental feasibility of our system.
We propose a novel scheme for generating N-qubit GHZ entangled state with a hybrid quantum system, which consists of N nitrogen-vacancy centers, N transmission line resonators, a current-biased Josephson junction superconducting qubit, and three kinds of interaction Hamiltonians. The proposal requires no adjustment of the qubit level spacings during the entire operation. Moreover, it is shown that the operation time is independent of the number of qubits. The present proposal is quite useful, and is a promising step to realize the large-sized quantum networks for quantum information processing and quantum computation.
Schemes for implementing quantum cloning are proposed with nitrogen-vacancy (N-V) centers in diamond confined in separated microtoroidal resonators via a single-photon input–output process and linear optics. By properly arranging and adjusting the linear optical elements to control the interaction between photons and N-V centers, we realize quantum cloning transformations, including the optimal symmetric 1→2 universal, phase-covariant, and 1→M economical phase-covariant ones. In these schemes, photons are used as data buses and information is copied from one N-V center to the other. We also discuss the cloning fidelities and dissipative effects. The results show that the present schemes are robust under the current experimental conditions.
An efficient scheme is proposed to implement a quantum cloning machine in separate cavities based on a hybrid interaction between electron-spin systems placed in the cavities and an optical coherent pulse. The coefficient of the output state for the present cloning machine is just the direct product of two trigonometric functions, which ensures that different types of quantum cloning machine can be achieved readily in the same framework by appropriately adjusting the rotated angles. The present scheme can implement optimal one-to-two symmetric (asymmetric) universal quantum cloning, optimal symmetric (asymmetric) phase-covariant cloning, optimal symmetric (asymmetric) real-state cloning, optimal one-to-three symmetric economical real-state cloning, and optimal symmetric cloning of qubits given by an arbitrary axisymmetric distribution. In addition, photon loss of the qubus beams during the transmission and decoherence effects caused by such a photon loss are investigated.