Andreas Neuzner

An elementary quantum network of single atoms in optical cavities

Quantum networks are distributed quantum many-body systems with tailored topology and controlled information exchange. They are the backbone of distributed quantum computing architectures and quantum communication. Here we present a prototype of such a quantum network based on single atoms embedded in optical cavities. We show that atom–cavity systems form universal nodes capable of sending, receiving, storing and releasing photonic quantum information. Quantum connectivity between nodes is achieved in the conceptually most fundamental way—by the coherent exchange of a single photon. We demonstrate the faithful transfer of an atomic quantum state and the creation of entanglement between two identical nodes in separate laboratories. The non-local state that is created is manipulated by local quantum bit (qubit) rotation. This efficient cavity-based approach to quantum networking is particularly promising because it offers a clear perspective for scalability, thus paving the way towards large-scale quantum networks and their applications.

Efficient teleportation between remote single-atom quantum memories.

We demonstrate teleportation of quantum bits between two single atoms in distant laboratories. Using a time-resolved photonic Bell-state measurement, we achieve a teleportation fidelity of (88.0 ± 1.5)%, largely determined by our entanglement fidelity. The low photon collection efficiency in free space is overcome by trapping each atom in an optical cavity. The resulting success probability of 0.1% is almost 5 orders of magnitude larger than in previous experiments with remote material qubits. It is mainly limited by photon propagation and detection losses and can be enhanced with a cavity-based deterministic Bell-state measurement.

Interference and dynamics of light from a distance-controlled atom pair in an optical cavity

Unconventional interference and statistics of photon fields are studied using two-state 87Rb atoms interacting with photons in an optical cavity. The observations are well described by the Tavis-Cummings model in the strong-coupling regime.

Generation of single photons from an atom-cavity system

A single rubidium atom trapped within a high-finesse optical cavity is an efficient source of single photons. We theoretically and experimentally study single-photon generation using a vacuum stimulated Raman adiabatic passage. We experimentally achieve photon generation efficiencies of up to 34

Decoherence-protected memory for a single-photon qubit

%

Breakdown of atomic hyperfine coupling in a deep optical-dipole trap

and 56

Long-coherence-time qubit memory: Combining an efficient light-atom interface and low-decoherence atomic states

%

Quantum networks based on single atoms in optical cavities

on the

Can Quantum Memories operate at Room Temperature

{D}_{1}

Coherent shaping of photons using electromagnetically induced transparency

and