Transfer and teleportation of quantum states encoded in decoherence-free subspace

Abstract

Quantum state transfer and teleportation, with qubits encoded in internal states of the atoms in cavities, among spatially separated nodes of a quantum network in decoherence-free subspace are proposed, based on a cavity-assisted interaction by single-photon pulses. We show in details the implementation of a logic-qubit Hadamard gate and a two-logic-qubit conditional gate, and discuss the experimental feasibility of our scheme.PACS numbers: 03.67. Hk, 42.50.Dv Quantum state transfer and teleportation are significant components in quantum information processing, especially for quantum network. As the confined atoms in cavity QED system are well suited for storing qubits in long-lived internal states, spatially separated cavities could be used to build a quantum network assisted by photons [1,2,3,4,5,6,7,11]. On the other hand, decoherence due to the inevitable interaction with environment destroys quantum coherence. So decoherence-free subspaces (DFSs) of Hilbert space has been introduced to protect against some errors due to environmental coupling with certain symmetry [8,9,10]. For example, Ref.[10] utilized two atoms to encode single-logic-qubit, i.e.,, which are robust to collective dephasing error caused by ambient magnetic fluctuation.In this Brief Report, for the quantum state encoded in DFS mentioned above, we present implementation of single-logic-qubit Hadamard gate and two-logic-qubit conditional gate based on cavity-assisted interaction with single-photon pulses. Based on these gates, we will carry out the quantum state transfer and teleportation between two spatially separated nodes in a quantum network. Compared with previous related works, our proposal does not rely on the synchronous optical lattices [4] in implementation of the single-logic-qubit Hadamard gate. In addition, auxiliary entangled photon pairs, as employed in [5], are unnecessary in our two-logic-qubit conditional gate. Moreover, for quantum state transfer, neither the entangled photon pairs [11] nor the special time-symmetric wave packet of the photons [1] is necessary in our scheme. So our scheme could not only protect quantum information from some decoherence, but also reduce the experimental difficulty compared to the previous schemes [1,4,5,11]. Furthermore, in our scheme, each node of the quantum network in DFS has individual input port for photons to complete necessary operations, and different operational results can be distinguished by * Electronic address: huawei.hw@gmail.com † Electronic address: mangfeng1968@yahoo.com detecting output photons.The main idea using cavity-assisted photon scattering to realize a controlled phase flip (CPF) between two atoms [3,4,5,6,11], is sketched below. Suppose that two identical atoms, each of which has a three-level configuration, are well located in a high-finesse cavity. The levels |0 and |e of the atom are resonantly coupled by the bare cavity mode with h polarization or by the h component of an input photon, while level |1 is decoupled because of the large detuning, as shown in Fi...

Quantum information processing in collective-rotating decoherence-free subspace

“…Moreover, we should point out that, similar to the QIP proposals in CDDFS presented in Refs. [10][11][12][13][14], the state may evolve out of the DFS momentarily during the process to construct the HCPF gate between photon and logic qubit in our proposal. The only way to reduce this negative influence to the least extent is to perform operations as fast as we can during the process to construct this HCPF gate.…”

“…However, the schemes in Refs. [8,[10][11][12][13][14] are immune to σ z -type noise but not immune to σ x -type noise. The schemes in Refs.…”

“…Then, Deng et al [11] proposed schemes to generate W state, Greenberger-Horne-Zeilinger state and cluster state in CDDFS. After that, Wei et al [12,13] proposed schemes to construct a modified many-logicqubit conditional phase gate and realize transfer and teleportation of quantum states in CDDFS . In 2010, Chen and Feng proposed a scheme to realize QIP with low-Q cavities in the same DFS [14].…”

Controlling Sudden Birth and Sudden Death of Entanglement at Finite Temperature

“…Entanglement, is now viewed as a physical resource, which provides a means to perform quantum computation and quantum communication [1][2][3][4][5][6][7][8]. Therefore, great efforts have been made to investigate entanglement characterization, entanglement control, and entanglement production in solid-state systems such as CQED and spin chains [9][10][11][12][13][14][15][16].…”

Cluster State Entanglement of Semiconductor Quantum Dots Based on Faraday Rotation

“…Concretely speaking, we need the microcavity-embedded single-charged QD (i.e., only one excess electron in the conduction band of the QD). The spin state of the single-charged QD can be coherently operated by local the electromagnetic field [29][30][31][32][33][34], but for the distributed QIP, we prefer to use the nonlocal interactions between the photon and single-charged QDs for a quantum network [35][36][37][38]. We will show that the exciton induced Faraday rotation makes the spatially separate QDs into a distributed quantum network, assisted by cavity QED technology.…”