Distributed quantum sensing in a continuous-variable entangled network

Experiments demonstrate quantum phase sensing with a four-mode entangled state, reaching a measurement precision that is beyond what can be achieved by separate individual probes. Networking is integral to quantum communications(1) and has significant potential for upscaling quantum computer technologies(2). Recently, it was realized that the sensing performances of multiple spatially distributed parameters may also be enhanced through the use of an entangled quantum network(3-10). Here, we experimentally demonstrate how sensing of an averaged phase shift among four distributed nodes benefits from an entangled quantum network. Using a four-mode entangled continuous-variable state, we demonstrate deterministic quantum phase sensing with a precision beyond what is attainable with separable probes. The techniques behind this result can have direct applications in a number of areas ranging from molecular tracking to quantum networks of atomic clocks.