Ability of unbounded pairs of observers to achieve quantum advantage in random access codes with a single pair of qubits

TL;DR

This paper demonstrates that multiple independent pairs of observers can sequentially achieve quantum advantage in random access codes using a single pair of qubits, even with projective measurements and separable states.

Contribution

It shows that unbounded pairs of observers can sequentially demonstrate quantum advantage in random access codes with a single qubit pair, a novel extension of quantum advantage scenarios.

Findings

Multiple observer pairs can achieve quantum advantage sequentially.

Quantum advantage persists with projective measurements and separable states.

Unbounded pairs of observers can demonstrate quantum advantage.

Abstract

Complications in preparing and preserving quantum correlations stimulate recycling of a single quantum resource in information processing and communication tasks multiple times. Here, we consider a scenario involving multiple independent pairs of observers acting with unbiased inputs on a single pair of spatially separated qubits sequentially. In this scenario, we address whether more than one pair of observers can demonstrate quantum advantage in some specific $2 \rightarrow 1$ and $3 \rightarrow 1$ random access codes. Interestingly, we not only address these in the affirmative, but also illustrate that unbounded pairs can exhibit quantum advantage. Furthermore, these results remain valid even when all observers perform suitable projective measurements and an appropriate separable state is initially shared.