Experimental Extraction of Secure Correlations from a Noisy Private State

TL;DR

This paper experimentally demonstrates a noisy four-photon state that separates secure key content from distillable entanglement, validating a key aspect of quantum private state theory and showcasing a proof-of-principle quantum key distribution.

Contribution

It provides the first experimental realization of a private state with a separation between secure key and entanglement, and compares distillation strategies for key extraction.

Findings

Secure key can be extracted without distillable entanglement.

Distillation-based methods are less effective for key extraction.

Experimental validation of quantum private state theory.

Abstract

We report experimental generation of a noisy entangled four-photon state that exhibits a separation between the secure key contents and distillable entanglement, a hallmark feature of the recently established quantum theory of private states. The privacy analysis, based on the full tomographic reconstruction of the prepared state, is utilized in a proof-of-principle key generation. The inferiority of distillation-based strategies to extract the key is exposed by an implementation of an entanglement distillation protocol for the produced state.