Entangled-State Time Multiplexing for Multiphoton Entanglement Generation

Large-scale quantum entanglement endows quantum technologies with significant quantum advan- tages over their classical counterparts. Nevertheless, this power is rarely unleashed due to our practical inefficiency in generating multiphoton entanglement. Here, we implement an active entangled-state time-multiplexing method, which can generate 2n-photon entangled states with an exponential efficiency - enhancement factor of Bn-1. We experimentally achieve a multiplexing power of B=6.43 in preparing four-photon Greenberger-Horne-Zeilinger states with fidelities above 0.806(5), which is mainly limited by technical loss in multiplexing. Even with current multiplexing power, our method can readily boost the efficiency of preparing 12-photon entangled sources by a factor of6.435 approximate to 104. Our work demonstrates that entangled-state time multiplexing promises a path toward efficiently preparing and harnessing mul- tiphoton quantum entanglement for unprecedented large-scale quantum computation and high-precision quantum metrology.