Entanglement of spin waves among four quantum memories

TL;DR

This paper demonstrates the creation, storage, and transfer of high-fidelity four-partite entanglement among atomic memories and photonic channels, advancing quantum network capabilities.

Contribution

It introduces the first realization of multipartite entanglement among four quantum memories and their coherent transfer to photonic channels.

Findings

High-fidelity measurement-induced entanglement among four atomic memories

Coherent transfer of atomic entanglement to four photonic channels

Full characterization of quadripartite entanglement using quantum uncertainty relations

Abstract

Quantum networks are composed of quantum nodes that interact coherently by way of quantum channels and open a broad frontier of scientific opportunities. For example, a quantum network can serve as a `web' for connecting quantum processors for computation and communication, as well as a `simulator' for enabling investigations of quantum critical phenomena arising from interactions among the nodes mediated by the channels. The physical realization of quantum networks generically requires dynamical systems capable of generating and storing entangled states among multiple quantum memories, and of efficiently transferring stored entanglement into quantum channels for distribution across the network. While such capabilities have been demonstrated for diverse bipartite systems (i.e., N=2 quantum systems), entangled states with N > 2 have heretofore not been achieved for quantum interconnects that coherently `clock' multipartite entanglement stored in quantum memories to quantum channels. Here, we demonstrate high-fidelity measurement-induced entanglement stored in four atomic memories; user-controlled, coherent transfer of atomic entanglement to four photonic quantum channels; and the characterization of the full quadripartite entanglement by way of quantum uncertainty relations. Our work thereby provides an important tool for the distribution of multipartite entanglement across quantum networks.