Cavity QED with atomic mirrors (1201.0643v3)

Abstract: A promising approach to merge atomic systems with scalable photonics has emerged recently, which consists of trapping cold atoms near tapered nanofibers. Here, we describe a novel technique to achieve strong, coherent coupling between a single atom and photon in such a system. Our approach makes use of collective enhancement effects, which allow a lattice of atoms to form a high-finesse cavity within the fiber. We show that a specially designated "impurity" atom within the cavity can experience strongly enhanced interactions with single photons in the fiber. Under realistic conditions, a "strong coupling" regime can be reached, wherein it becomes feasible to observe vacuum Rabi oscillations between the excited impurity atom and a single cavity quantum. This technique can form the basis for a scalable quantum information network using atom-nanofiber systems.

• The paper introduces a novel cavity QED approach where periodic atomic lattices act as mirrors to enable strong collective atom-photon coupling.
• It leverages cold atoms in nanofiber traps to achieve an effective cavity finesse of about 10^2, markedly reducing traditional finesse requirements.
• The method offers a scalable framework for quantum networks by facilitating efficient quantum state storage, retrieval, and nonlinear photon interactions.

Cavity QED with Atomic Mirrors: A Pathway to Scalable Quantum Networks

The paper "Cavity QED with atomic mirrors" by Chang et al. delineates a novel method for achieving strong coherent interactions between single atoms and photons by leveraging collective enhancement effects in atomic lattices. This method posits a new avenue for integrating atomic systems with scalable photonics, laying the groundwork for robust quantum information networks.

Core Concepts and Methodology

The paper emphasizes a hybrid approach that amalgamates the beneficial attributes of three predominant methods in quantum information science: cavity quantum electrodynamics (QED), coherent atomic ensemble interactions, and tight focusing of optical fields. Specifically, the approach envisions trapping cold atoms near tapered nanofibers to form high-finesse cavities through collective atomic enhancements. This arrangement allows an impurity atom to experience enhanced interactions with single photons.

The system under consideration consists of atoms positioned in a lattice structure with periodic spacing that acts as a Bragg mirror for incident photons. Notably, this lattice facilitates a strong coupling regime whereby the coupled system can manifest the haLLMark of cavity QED—vacuum Rabi oscillations. The paper establishes a comparison between this proposed system and the conventional cavity QED, wherein atomic mirrors exhibit long relaxation times and are highly dispersive, in contrast to the traditional high-finesse mirrors required for strong coupling.

Key Numerical Findings

Chang et al. identify several numerical benchmarks demonstrating the efficacy of their model:

• A lattice comprising $N_M$ atoms can reflect incident photons with high efficiency, even if single atoms predominantly exhibit absorption.
• The collective mode of atomic mirrors shows an effective cavity finesse $F \sim 10^2$ that remains sufficient to reach the strong coupling regime, a stark reduction compared to $F \gtrsim 10^5$ needed in conventional setups.
• The paper details the normal mode splitting in the cavity spectral response, which scales with $\sqrt{N_A}$ where $N_A$ is the atom number in the mirror, illustrating the scalability of this configuration.

Implications and Future Directions

This research offers substantial theoretical and practical implications for quantum information processing:

1. Quantum Networks: The architecture introduced facilitates the creation of scalable quantum networks, with photonic quantum information effectively interfaced with atomic nodes.
2. Quantum Memory: The framework supports the storage and retrieval of quantum states in atoms, a critical component for quantum repeaters and long-distance quantum communication.
3. Nonlinear Photon Dynamics: The potential to explore many-body dynamics and non-linear photon interactions opens possibilities for novel quantum phases and applications in quantum simulations.

Looking forward, this work paves the way for experimental realizations using engineered photonic structures such as photonic crystals, offering tailored phase shifts and enhanced atom-photon coupling. This move toward practical applications underscores the role of this research in advancing quantum technology paradigms and meeting the demands of future quantum networks.