Quantum cloning in coupled states of optical field and atomic ensemble by quasi-condensation of polaritons

A scheme for the optimal Gaussian cloning of coherent light states at the light-atoms interface is proposed. The distinct feature of this proposal is that the clones are stored in an atomic quantum memory, which is important for applications in quantum communication. The atomic quantum cloning machine requires only a single passage of the light pulse through the atomic ensembles followed by the measurement of a light quadrature and an appropriate feedback, which renders the p...

I analyze an all-optical switching scheme in a cavity QED system consisting of multiple three-level atoms confined in a cavity mode. A control laser coupled to the atoms from free space induces quantum interference in the coupled cavity-atom system and performs all optical switching of the cavity-atom polaritons. When the cavity is tuned far away from the atomic resonance, the cavity-atom polariton consists of nearly pure photonic excitation and then the scheme can be used fo...

We study the problem of high temperature Bose-Einstein condensation (BEC) of atom-light polaritons in a waveguide cavity appearing due to interaction of two-level atoms with (non-resonant) quantized optical radiation, in the strong coupling regime, in the presence of optical collisions (OCs) with buffer gas particles. Specifically, we propose a special biconical waveguide cavity (BWC), permitting localization and trapping of low branch (LB) polaritons imposed by the variation...

We present a feasible scheme to implement the $1 \to 2$ optimal cloning of arbitrary single particle atomic state into two photonic states, which is important for applications in long distance quantum communication. Our scheme also realizes the tele-NOT gate of one atom to the other distant atom trapped in another cavity. The scheme is based on the adiabatic passage and the polarization measurement. It is robust against a number of practical noises such as the violation of th...

We propose an interesting scheme for distributed orbital state quantum cloning with atomic ensembles based on the quantum Zeno dynamics. These atomic ensembles which consist of identical three-level atoms are trapped in distant cavities connected by a single-mode integrated optical star coupler. These qubits can be manipulated through appropriate modulation of the coupling constants between atomic ensemble and classical field, and the cavity decay can be largely suppressed as...

Here we present an experimentally feasible scheme to entangle flying qubit (individual photon with polarization modes) and stationary qubit (atomic ensembles with long-lived collective excitations). This entanglement integrate two different species can act as a critical element for the coherent transform of quantum information between flying and stationary qubits. The entanglement degree can be also adjusted expediently with linear optics. Furthermore, the present scheme can ...

We propose a scheme to generate cluster states of atomic qubits by using cavity quantum electrodynamics (QED) and linear optics, in which each atom is confined in a resonant optical cavity with two orthogonally polarized modes. Our scheme is robust to imperfect factors such as dissipation, photon loss, and detector inefficiency. Discussions are made for experimental feasibility of our scheme.

A telecom photon is a suitable information carrier in a fiber-based quantum network due to its lower transmission loss in fiber. Because of the paucity of suitable atomic system, usually the photon connecting different memories is in near infrared band, therefore the frequency conversion of the photon in and out of telecomband has to be required to realize the interface between the atomic-based memory and the photon-based carrier. In order for that, two atomic or other system...

We investigate a scheme of atomic quantum memory to store photonic qubits of polarization in cavity QED. It is observed that the quantum-state swapping between a single-photon pulse and a $ \Lambda $-type atom can be made via scattering in an optical cavity [T. W. Chen, C. K. Law, P. T. Leung, Phys. Rev. A {\bf 69} (2004) 063810]. This swapping operates limitedly in the strong coupling regime for $ \Lambda $-type atoms with equal dipole couplings. We extend this scheme in cav...

An efficient quantum storage is highly desired for quantum information processing. As indicated by certain applications, a universal quantum storage is required to have a storage efficiency above 50% to beat the no-cloning limit. Although significant progress has been achieved in improving various quantum storage, the best storage efficiency of single photons is still below this criteria. By integrating a highly controllable single photon source with an optimized quantum stor...