Integrated Eu3+:Y2SiO5 quantum memories in fiber and waveguide microcavities achieve record efficiencies of 80.3% for coherent pulses and 69.8% for heralded single photons while storing 20 temporal modes.
A Metropolitan-scale Multiplexed Quantum Repeater with Bell Nonlocality
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abstract
Quantum repeaters can overcome exponential photon loss in optical fibers, enabling heralded entanglement between distant quantum memories. The definitive benchmark for this entanglement is Bell nonlocality; however, recent metropolitan-scale demonstrations based on single-photon interference (SPI) schemes have been limited to generating low-quality entanglement, falling short of Bell nonlocality certification. Here, we introduce a multiplexed quantum repeater protocol based on time measurements (MQR-TM), successfully combining the high heralding rate of SPI schemes with the phase robustness of two-photon interference (TPI) schemes. This approach achieves heralded entanglement distribution between two solid-state quantum memories over a record 14.5~km separation, generating a Bell state with a fidelity of $78.6 \pm 2.0\%$. We observe a CHSH-Bell inequality violation by 3.7 standard deviations, marking the first certification of Bell nonlocality in metropolitan-scale quantum repeaters. Our architecture supports autonomous quantum node operation without fiber channel phase stabilization, offering a practical framework for scalable quantum-repeater networks.
fields
quant-ph 2years
2025 2verdicts
CONDITIONAL 2representative citing papers
The first measurement of coherence in an excited-state optical transition in a rare-earth doped crystal yields a maximum coherence time of 4.75 μs at telecom wavelength.
citing papers explorer
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Efficient integrated quantum memory for light
Integrated Eu3+:Y2SiO5 quantum memories in fiber and waveguide microcavities achieve record efficiencies of 80.3% for coherent pulses and 69.8% for heralded single photons while storing 20 temporal modes.
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Spectroscopy and Coherence of an Excited-State Transition in Tm$^{3+}$:YAlO$_3$ at Telecommunication Wavelength
The first measurement of coherence in an excited-state optical transition in a rare-earth doped crystal yields a maximum coherence time of 4.75 μs at telecom wavelength.