Quantum information and atomic networks

Harry J. Kimble

Quantum networks for the processing and distribution of quantum information could consist of quantum “nodes” for the manipulation and storage of quantum information, with these nodes linked by quantum “channels” for the transmission of quantum states. The leading proposal for the realization of such networks utilizes atoms within optical cavities as the “nodes.” Conversion of internal atomic state information into optical photons that propagate from one cavity to another forms the basis for the “channels.” Unfortunately, even in terms of laboratory “proof-of-principle” demonstrations, technical capabilities are far short of those required to implement such quantum networks. However, along the road to these ends, there lies a rich set of scientific problems that are the subject of this paper, including nonlinear optics with single atoms and photons, trapping of individual atoms within high finesse optical cavities, and teleportation of quantum states.

A. Kuzmich, T. Chanelière, Dzmitry Matsukevich

Dirk Bouwmeester, ARTUR K. EKERT, Anton Zeilinger

Mikhail I. Shalaev, Sagnik Saha, George Toh +6 more

Quantum networking enables the exchange of quantum information between physically separated quantum systems, which has applications ranging from quantum computing to unconditionally secure communication. These quantum information is generally represented by two-level quantum systems or qubits. Here, we demonstrate a quantum network of high-dimensional (HD) quantum memories or "qudits" stored in individual atoms. The interference and detection of HD time-bin-encoded single photons emitted from atomic qudit memories herald maximally entangled Bell states across pairs of atomic qudit levels. This approach expands the quantum information capacity of a quantum network while improving the entanglement success fraction beyond the standard 50% limit of qubit-based measurement protocols.

Bi Qiao, Fang Jin-Qing, Liu Gui-ping

Xihua Yang, Bolin Xue, Junxiang Zhang +1 more

Entanglement provides an essential resource for quantum computation, quantum communication, and quantum networks. How to conveniently and efficiently realize the generation, distribution, storage, retrieval, and control of multipartite entanglement is the basic requirement for realistic quantum information processing. Here, we present a theoretical proposal to efficiently and conveniently achieve a universal quantum information processor (QIP) via atomic coherence in an atomic ensemble. The atomic coherence, produced through electromagnetically induced transparency (EIT) in the Λ-type configuration, acts as the QIP and has full functions of quantum beam splitter, quantum frequency converter, quantum entangler, and quantum repeater. By employing EIT-based nondegenerate four-wave mixing processes, the generation, exchange, distribution, and manipulation of light-light, atom-light, and atom-atom multipartite entanglement can be efficiently and flexibly achieved in a deterministic way with only coherent light fields. This method greatly facilitates the operations in quantum information processing, and holds promising applications in realistic scalable quantum communication and quantum networks.