Remote state-of-polarization control in polarization-maintaining fibre

Yan‐Ling Li, Mao-Fa Fang, Xing Mao Xiao +1 more

We propose a scheme for implementing a remote three-qubit controlled-Z gate with three atoms separately trapped in three distant cavities coupled by optical fibres. The influences of various decoherence processes, such as spontaneous emission of the atoms and photon leakage of the cavities and the optical fibres, on the fidelity are also investigated. It is found that the gate can be implemented with high fidelity even when these decoherence processes are considered. This scheme can be extended to the implementation of a remote N -qubit controlled-Z gate with N atoms separately trapped in N distant cavities coupled by optical fibres.

Marco Santagiustina, Andrea Galtarossa, Luca Palmieri +3 more

D. Clarke, J. F. Grainger

Muhammad Abdullah Butt, Paul Roth, George K. Wong +7 more

Polarization-preserving fibers maintain the two polarization states of an orthogonal basis. Quantum communication, however, requires sending at least two nonorthogonal states and these cannot both be preserved. We present a new scheme that allows for using polarization encoding in a fiber not only in the discrete, but also in the continuous-variable regime. For the example of a helically twisted photonic-crystal fibre, we experimentally demonstrate that using appropriate nonorthogonal modes, the polarization-preserving fiber does not fully scramble these modes over the full Poincaré sphere, but that the output polarization will stay on a great circle; that is, within a one-dimensional protected subspace, which can be parametrized by a single variable. This will allow for more efficient measurements of quantum excitations in nonorthogonal modes.

R. J. Ballagh, Christian G. Parigger

Jieli Yan, Xiaoyu Zhou, Zhihui Yan +1 more

Quantum teleportation is a building block in quantum computation and quantum communication. The continuous-variable polarization squeezed state is a key resource in quantum networks, offering advantages for long-distance distribution and direct interfacing of quantum nodes. Although polarization squeezed state has been generated and distributed between remote users, it is a long-standing goal to implement controlled quantum teleportation of the polarization squeezed state with multiple remote users. Here, we propose a feasible scheme to teleport a polarization squeezed state among multiple remote users under control. The polarization state is transferred between different remote quantum networks, and the controlled quantum teleportation of the polarization state can be implemented in one quantum network involving multiple remote users. The results show that such a controlled quantum teleportation can be realized with 36 users through about 6-km free-space or fiber quantum channels, where the fidelity of 0.352 is achieved beyond the classical limit of 0.349 with an input squeezing variance of 0.25. This scheme provides a direct reference for the experimental implementation of remote and controlled quantum teleportation of polarization states, thus enabling more teleportation-based quantum network protocols.