Hong–Ou–Mandel interference linking independent room-temperature quantum memories

To realize a large-scale quantum network,both quantum memory and the interference of retrieved indistinguishable photons are essentially required to perform multi-photon synchronization and quantum-interference-mediated entanglement swapping.Significant progress has been achieved in low-temperature and well-isolated systems.However,linking independent quantum memories at room temperature remain challenging.Here,we present an experimental demonstration of Hong–Ou–Mandel interference between single photons from two independent room-temperature quantum memories.We manage to simultaneously operate two such quantum memories and individually obtain a memory-built-in quantum correlation of Stokes and anti-Stokes photons by a far-off-resonance Duan–Lukin–Cirac–Zoller protocol.We also successfully enhance the Hong–Ou–Mandel interference rate up to about 15 times by increasing each photon rate,which is achieved by coordinating two quantum memories with a repeat-until-success fashion.We observe the visibility of quantum interference up to 75.0%without reduction of any background noise,well exceeding the classical limit of 50%.Our results,together with its straightforward,broadband,and room-temperature features,open up a promising way towards realizing large-scale quantum networks at ambient conditions.

Quantum advantage with membosonsampling

Quantum computer,harnessing quantum superposition to boost a parallel computational power,promises to outperform its classical counterparts and offer an exponentially increased scaling.The term“quantum advantage”was proposed to mark the key point when peo-ple can solve a classically intractable problem by artificially control-ling a quantum system in an unprecedented scale,even without er-ror correction or known practical applications.Boson sampling,a problem about quantum evolutions of multi-photons on multimode photonic networks,as well as its variants,has been considered as a promising candidate to reach this milestone.However,the current photonic platforms suffer from the scaling problems,both in pho-ton numbers and circuit modes.Here,we propose a new variant of the problem,membosonsampling,exploiting the scaling of the prob-lem can be in principle extended to a large scale.We experimentally verify the scheme on a self-looped photonic chip inspired by mem-ristor,and obtain multi-photon registrations up to 56-fold in 750,000 modes with a Hilbert space up to 10254.The results exhibit an inte-grated and cost-efficient shortcut stepping into the“quantum advan-tage”regimeina photonic systemfarbeyondpreviousscenarios,and provide a scalable and controllable platform for quantum information processing.