First on-chip multipartite entanglement achieved with optical microcomb

A recent study has realized multipartite entanglement on an optical chip for the first time, constituting a significant advance for scalable quantum information. The paper, titled “Continuous-variable multipartite entanglement in an integrated microcomb,” is published in Nature.

Led by Professor Wang Jianwei and Professor Gong Qihuang from the School of Physics at Peking University, in collaboration with Professor Su Xiaolong’s research team from Shanxi University, the research has implications for quantum computation, networking and metrology.

Continuous-variable integrated quantum photonic chips have been confined to the encoding of and entanglement between two qumodes, a bottleneck withholding the generation or verification of multimode entanglement on chips. Additionally, past research on cluster states failed to go beyond discrete viable, leaving a gap in the generation and detection of continuous-variable entanglement on photonic chips.

This study marks an unprecedented deterministic generation, manipulation and detection of continuous-variable multipartite entanglement on an integrated-optical quantum chip.

Among the key findings is on-chip deterministic generation of continuous-variable multipartite entanglement in an integrated optical microcomb: polychromatic pump and polychromatic homodyne detection technologies (see Fig. 1c) produce multimode squeezed-vacuum optical frequency combs below the threshold of parametric oscillation, demonstrating the chip-scale deterministic generation of continuous-variable multipartite entanglement.

In addition, the team completed the characterization and reconfiguration of multipartite entanglement with different cluster-type structures. Tailoring the local oscillator beams made it possible to generate various cluster-type entanglement structures, including the four-qumode linear-, box- and star- entanglement structures, and the six-qumode linear-type entanglement structure.

The continuous-variable cluster-style entanglement structure was also experimentally verified. Through precisely tailoring the intensity and detuning of polychromatic pumps, combined with linearly operating the polychromatic local oscillators, the off-diagonal nullifier correlations of different entanglement structures were sufficiently lowered. The research demonstrated the chip-scale deterministic generation of continuous-variable multipartite entanglement, as well as the accurate measurement of various entanglement structures.

The continuous-variable integrated quantum photonics (CVIQP) technologies reported in this study provide a solution to the scalability challenges in terms of integrated quantum photonics chips, enabling the generation and manipulation of large-scale entanglement. Meanwhile, the results represent a remarkable leap in chip-scale quantum sensing, networking, and computing.