Engineering topics

Bin, Shao

Publications and source records attributed to Bin, Shao.

7 records

DOE OSTI2011

Duplex quantum communication through a spin chain

Data multiplexing within a quantum computer can allow for the simultaneous transfer of multiple streams of information over a shared medium thereby minimizing the number of channels needed for requisite data transmission. Here, we investigate a two-way quantum communication protocol using a spin chain placed in an external magnetic field. In our scheme, Alice and Bob each play the role of a sender and a receiver as two states, cos(({theta}{sub 1}/2))0+sin(({theta}{sub 1}/2))e{sup i{phi}{sub 1}}1 and cos(({theta}{sub 2}/2))0+sin(({theta}{sub 2}/2))e{sup i{phi}{sub 2}}1, are transferred through one channel simultaneously. We find that the transmission fidelity at each end of a spin chain can usually be enhanced by the presence of a second party. This is an important result for establishing the viability of duplex quantum communication through spin chain networks.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Quantum correlation transfer through two parallel XXZ spin chains with phase shift control

Transmitting quantum states and entanglement through quantum channels is one of the key requirements for the development of quantum computation. Quantum discord has received much attention in quantum computation. We transfer quantum discord through two parallel XXZ spin chains with phase shift. The maximum discord can be enhanced by the phase shift. It will take more time to obtain an enhanced maximum discord in some cases, but for other cases, both the maximum and speed are enhanced by the phase shift. In the thermodynamic limit, the effect of the phase shift disappears and the maximum discord exponentially decays with increasing of the receiving position. Our results on spin chains are generalized to a family of linear Hamiltonians.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Quantum and classical correlations in the one-dimensional XY model with Dzyaloshinskii-Moriya interaction

We study the effect of Dzyaloshinskii-Moriya (DM) interaction on pairwise quantum discord, entanglement, and classical correlation in the anisotropic XY spin-half chain. Analytical expressions for both quantum and classical correlations are obtained from the spin-spin correlation functions. These pairwise quantities exhibit interesting behaviors in relation to the relative strengths of the physical parameters. For the infinite chain, we show that the quantum discord can be useful to highlight the quantum phase transition, especially for the long-distance spins, where entanglement decays rapidly. We observe nonanalyticities of the derivatives of both quantum and classical correlations with respect to the magnetic intensity at the critical point; interestingly, the DM interaction weakens the critical behavior in the derivatives of these correlations. While the DM interaction suppresses the standard behaviors of the XY model, it enhances surprisingly the pairwise entanglement for the third nearest neighbor spins.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Effective method of calculating the non-Markovianity N for single-channel open systems

We propose an effective method which can simplify the optimization of the increase of the trace distance over all pairs of initial states in calculating the non-Markovianity N for single-channel open systems. For the amplitude-damping channel, we can unify the results of Breuer et al. [Phys. Rev. Lett. 103, 210401 (2009)] in the large-detuning case and the results of Xu et al. [Phys. Rev. A 81, 044105 (2010)] in the resonant case; furthermore, for the general off-resonant cases, we can obtain a very tight lower bound of N. As another application of our method, we also discuss Nfor the non-Markovian depolarizing channel.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Quantum discord for a central two-qubit system coupled to an XY-spin-chain environment

We investigate the dynamic behaviors of quantum discord for a central two-qubit system coupled to an XY-spin-chain environment. In the weak-coupling regime, we show that the quantum discord for the two central qubits can become minimized rapidly close to the critical point of a quantum phase transition. By considering the two qubits that are initially prepared in the Werner state, we study the evolution of the quantum discord and that of entanglement under the same conditions. Our results imply that entanglement can disappear completely after a finite time, while the quantum discord decreases and tends to be a stable value according to the initial-state parameter for a very-long-time interval. In this sense, the quantum discord is more robust than entanglement for the quantum system exposed to the environment. The relation between the quantum correlations and the classical correlation is also shown for two particular cases.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Perfect function transfer in two and three dimensions without initialization

We find analytic models that can perfectly transfer, without state initialization or remote collaboration, arbitrary functions in two- and three-dimensional interacting bosonic and fermionic networks. This provides for the possible experimental implementation of state transfer through bosonic or fermionic atoms trapped in optical lattices. A significant finding is that the state of a spin qubit can be perfectly transferred through a fermionic system. Families of Hamiltonians are described that are related to the linear models and that enable the perfect transfer of arbitrary functions. Furthermore, we propose methods for eliminating certain types of errors.

36 MATERIALS SCIENCE↗

DOE OSTI2010

Entanglement evolution of two qubits under noisy environments

The entanglement evolution of two qubits under local, single-, and two-sided noisy channels is investigated. It is found that for all pure initial states, the entanglement under a one-sided noisy channel is completely determined by the maximal trace distance which is the main element to construct the measure of non-Markovianity. For the two-sided noisy channel case, when the qubits are initially prepared in a general class of states, either pure or mixed, the entanglement can be expressed as the product of the initial entanglement and the channels' action on the maximally entangled state.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗