Experimental single-copy distillation of quantumness from higher-dimensional entanglement

TL;DR

This paper demonstrates how single-copy local filtering can recover and enhance the quantumness of higher-dimensional entangled states, enabling their certification and utility in quantum information tasks.

Contribution

It provides the first experimental proof that single-copy operations can activate and certify the nonlocal and useful properties of higher-dimensional entangled states.

Findings

Successfully certified Bell-nonlocality of two-qutrit Werner states.

Activated usefulness for quantum teleportation and dense coding.

Enhanced quantum steerability and discrimination capabilities.

Abstract

Entanglement is at the heart of quantum theory and is responsible for various quantum-enabling technologies. In practice, during its preparation, storage, and distribution to the intended recipients, this valuable quantum resource may suffer from noisy interactions that reduce its usefulness for the desired information-processing tasks. Conventional schemes of entanglement distillation aim to alleviate this problem by performing collective operations on multiple copies of these decohered states and sacrificing some of them to recover Bell pairs. However, for this scheme to work, the states to be distilled should already contain a large enough fraction of maximally entangled states before these collective operations. Not all entangled quantum states meet this premise. Here, by using the paradigmatic family of two-qutrit Werner states as an exemplifying example, we experimentally demonstrate how one may use single-copy local filtering operations to meet this requirement and to recover the quantumness hidden in these higher-dimensional states. Among others, our results provide the first proof-of-principle experimental certification of the Bell-nonlocal properties of these intriguing entangled states, the activation of their usefulness for quantum teleportation, dense coding, and an enhancement of their quantum steerability, and hence usefulness for certain discrimination tasks. Our theoretically established lower bounds on the steering robustness of these states, when they admit a symmetric quasiextension or a bosonic symmetric extension, and when they show hidden dense-codability may also be of independent interest.