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 $F_{\mathrm{gate}}\approx 99.93\%$ ; (ii)~atom--photon conversion through Raman emission from an oblate spheroidal ensemble, yielding directional emission efficiency $η_{\mathrm{dir}}\approx 73\%$ and single-node efficiency $η_{\mathrm{node}}\approx 40\%$ ; 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 $M\approx 100$ retry attempts within a coherence time $T_2>100\,μ\mathrm{s}$ , enabling entanglement generation rates of approximately $4\,\mathrm{kHz}$ 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.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 $F_{\mathrm{gate}}\approx 99.93\%$; (ii)~atom--photon conversion through Raman emission from an oblate spheroidal ensemble, yielding directional emission efficiency $η_{\mathrm{dir}}\approx 73\%$ and single-node efficiency $η_{\mathrm{node}}\approx 40\%$; 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 $M\approx 100$ retry attempts within a coherence time $T_2>100\,μ\mathrm{s}$, enabling entanglement generation rates of approximately $4\,\mathrm{kHz}$ 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.

quant-pharXiv:2603.14854Mar 17, 20260 citations

Unconventional quantum gate based on Rydberg blockade mechanism

RongHui Sun, Ming-Yong Ye, Xiu‐Min Lin

Science China Physics Mechanics and AstronomyJul 12, 20134 citations

Quantum computing with cold atoms and Rydberg blockade

Mark E. Saffman

Bulletin of the American Physical SocietyJun 11, 20150 citations

Measurement-Device-Independent Verification of a Quantum Memory

Yong Hui Yu, Peng-Fei Sun, Yuzhe Zhang +9 more

In this Letter we report an experiment that verifies an atomic-ensemble quantum memory via a measurement-device-independent scheme. A single photon generated via Rydberg blockade in one atomic ensemble is stored in another atomic ensemble via electromagnetically induced transparency. After storage for a long duration, this photon is retrieved and interfered with a second photon to perform a joint Bell-state measurement (BSM). The quantum state for each photon is chosen based on a quantum random number generator, respectively, in each run. By evaluating correlations between the random states and BSM results, we certify that our memory is genuinely entanglement preserving.In this Letter we report an experiment that verifies an atomic-ensemble quantum memory via a measurement-device-independent scheme. A single photon generated via Rydberg blockade in one atomic ensemble is stored in another atomic ensemble via electromagnetically induced transparency. After storage for a long duration, this photon is retrieved and interfered with a second photon to perform a joint Bell-state measurement (BSM). The quantum state for each photon is chosen based on a quantum random number generator, respectively, in each run. By evaluating correlations between the random states and BSM results, we certify that our memory is genuinely entanglement preserving.

arXiv:2104.14723Physical Review LettersOct 14, 202122 citations

F_{\mathrm{gate}}\approx 99.93\%

; (ii)~atom--photon conversion through Raman emission from an oblate spheroidal ensemble, yielding directional emission efficiency

η_{\mathrm{dir}}\approx 73\%

and single-node efficiency

η_{\mathrm{node}}\approx 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\approx 100

retry attempts within a coherence time

T_2>100\,μ\mathrm{s}

, enabling entanglement generation rates of approximately

4\,\mathrm{kHz}

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.