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Curated by RSF Research Staff

Quantum memories for a quantum internet network

Research on quantum communication is very active and a major improvement has been made recently in terms of Earth-to-Satellite Quantum Teleportation and Quantum Communications via Satellites. Another important subject concerns quantum memory, an essential element to build any quantum system and in particular for quantum networks.

Quantum networks built from optical fiber-linked quantum nodes open manifold opportunities like high-speed quantum cryptography networks, large scale quantum computers and quantum simulators. The requirements for a scalable quantum node technology are (i) storing quantum information in a quantum memory, and (ii) on demand conversion of this information into single photons traveling along the network interconnects. Many different physical platforms for quantum memories are currently under investigation, ranging from phonons in solids to atomic Bose-Einstein-condensates.

" The combination of a simple setup, high bandwidth and low noise level is very promising for future application in quantum networks."

Janik Wolters - University of Basel, Swiss

Physicist Janik Wolters and his team based at University of Basel have developed a quantum memory in warm Rb vapor with on-demand storage and retrieval [1].

(a) Energy levels of the Rb line and transitions involved in the memory experiments. (b) Experimental setup for the memory experiment. (c) Shape of the signal pulses used in the storage and retrieval experiments measured.

The researchers were able to store information and read them out again later without altering their quantum mechanical properties too much. This memory is working with single photons emitted by semiconductor quantum dots. Vapor cell memories offer an excellent compromise between storage efficiency, storage time, noise level, and experimental complexity, and atomic collisions have negligible influence on the optical coherences. Operation of the memory is demonstrated using attenuated laser pulses on the single photon level. Straightforward technological improvements can boost the end-to-end-efficiency and increasing the optical depth and exploiting the Zeeman substructure of the atoms will allow such a memory to approach near unity efficiency.

Charge state spectrum of in-trap created argon ions (left) and fine structure level scheme with Zeeman substructure of boron-like argon (right).

In the future, quantum networks could lead to unconditionally secure communication in metropolitan areas and network computing able to solve complex problems such as the simulation of large physical, chemical and biological systems.

Read more at:

[1] Simple Atomic Quantum Memory Suitable for Semiconductor Quantum Dot Single Photons

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