# Distillation of quantum steering

## TL;DR

This paper demonstrates a method to distill quantum steering, transforming weakly steerable states into perfectly steerable ones, with experimental validation showing significant improvements even with few copies, advancing quantum communication protocols.

## Contribution

The paper introduces the first deterministic steering distillation protocol, both theoretically and experimentally, achieving perfect steering in the asymptotic limit and improving steering in practical scenarios.

## Key findings

- Successfully distills quantum steering to a perfect singlet assemblage.
- Experimental demonstration with hyperentangled photon pairs confirms protocol efficacy.
- Protocol enhances steering even with limited copies, useful for noisy quantum networks.

## Abstract

We show -- both theoretically and experimentally -- that Einstein-Podolsky-Rosen steering can be distilled. We present a distillation protocol that outputs a perfectly correlated system -- the singlet assemblage -- in the asymptotic infinite-copy limit, even for inputs that are arbitrarily close to being unsteerable. As figures of merit for the protocol's performance, we introduce the assemblage fidelity and the singlet-assemblage fraction. These are potentially interesting quantities on their own beyond the current scope. Remarkably, the protocol works well also in the non-asymptotic regime of few copies, in the sense of increasing the singlet-assemblage fraction. We demonstrate the efficacy of the protocol using a hyperentangled photon pair encoding two copies of a two-qubit state. This represents to our knowledge the first observation of deterministic steering concentration. Our findings are not only fundamentally important but may also be useful for semi device-independent protocols in noisy quantum networks.