Quantum internet will enable a number of revolutionary applications, such as distributed quantum computing, large scale quantum communication and cooperative operation of atomic clocks. Cold atomic ensembles are a very promising approach for quantum internet, featuring long coherence time and collectively enhanced interaction with single photons. The current central theme in this direction is to improve the performance of fundamental building blocks and to construct small-scale networks which go beyond state of the art. In this talk, I will present our experimental works in this direction, such as the improvement of single-node performance with cavity enhancement, optical lattice, and Rydberg nonlinearity. I will also talk about the extension of atom-atom entanglement distance via quantum frequency conversion, and the establishment of entanglement among three quantum nodes via three-photon interference etc.
Realizing large-scale quantum networks requires the generation of high-fidelity quantum entanglement states between remote quantum nodes, a key resource for quantum communication, distributed computation and sensing applications. However, entanglement distribution between quantum network nodes is hindered by optical transmission loss and local operation errors. Here, we propose a novel quantum repeater architecture that synergistically integrates Rydberg atom quantum processors with optical cavities to overcome these challenges. Our scheme leverages cavity-mediated interactions for efficient remote entanglement generation, followed by Rydberg interaction-based entanglement purification and swapping. Numerical simulations, incorporating realistic experimental parameters, demonstrate the generation of Bell states with 99\% fidelity at rates of 1.1\,kHz between two nodes in local-area network (distance
0.1km), and can be extend to metropolitan-area (
25km) or intercity (
250km, with the assitance of frequency converters) network with a rate of 0.1\,kHz. This scalable approach opens up near-term opportunities for exploring quantum network applications and investigating the advantages of distributed quantum information processing.
Realizing large-scale quantum networks requires the generation of high-fidelity quantum entanglement states between remote quantum nodes, a key resource for quantum communication, distributed computation, and sensing applications. However, entanglement distribution between quantum network nodes is hindered by optical transmission loss and local operation errors. Here, we propose a quantum repeater architecture that synergistically integrates Rydberg-atom quantum processors with optical cavities to overcome these challenges. Our scheme leverages cavity-mediated interactions for efficient remote entanglement generation followed by Rydberg-interaction-based entanglement purification and swapping. Numerical simulations, incorporating realistic experimental parameters, demonstrate the generation of Bell states with 99% fidelity at rates of 1.1 kHz between two nodes in a local-area network (distance
0.1km), and can be extended to metropolitan-area (
25km) or intercity (
250km, with the assistance of frequency converters) networks with a rate of 0.1 kHz. This scalable approach opens up near-term opportunities for exploring quantum network applications and investigating the advantages of distributed quantum information processing.
Quantum repeaters are vital ingredients for realization of long-distance quantum networks [1]. They can be realized by preparing nodes that can generate an entangled light-matter state, namely, a single photon entangled to a quantum memory. This allows for entangling two distant quantum memories, by propagating the single photons from each node to an intermediate place for Bell state measurements. A common approach for generating such entangled light-matter states is generating an entangled photon pair in a nonlinear source, and coupling one of the photons in the pair to a quantum memory for storage [2]. However, such an approach faces two main challenges: Photon-pair generation in nonlinear sources is a probabilistic process. Moreover, due to modal and spectral mismatches, coupling single photons from a nonlinear source to a quantum memory is generally not an efficient process. These make the successful generation of an entangled light-matter state highly probabilistic.
We present a complete protocol for cavity-free quantum networking based on collective enhancement in Rydberg atom ensembles. The scheme combines Rydberg blockade, collectively enhanced light--matter coupling, and phase-matched directional emission to remove the need for optical cavities while retaining efficiencies comparable to cavity-assisted interfaces. The protocol proceeds in three steps: (i)~local control--ensemble entanglement generated by Rydberg blockade with gate fidelity
Fgate≈99.93%; (ii)~atom--photon conversion through Raman emission from an oblate spheroidal ensemble, yielding directional emission efficiency
ηdir≈73% and single-node efficiency
ηnode≈40%; and (iii)~remote atom--atom entanglement via Hong--Ou--Mandel interference, producing Bell states with fidelity
F>97.5%. Incorporating quantum memories allows up to
M≈100 retry attempts within a coherence time
T2>100μs, enabling entanglement generation rates of approximately
4kHz over a 20~km separation. Collectively enhanced Rydberg ensembles thus provide a practical, cavity-free interface for scalable distributed quantum computing and secure quantum communication.