Quantum Random Access Codes for Boolean Functions

TL;DR

This paper introduces a generalized framework for random access codes that recover Boolean functions on subsets of bits, analyzing quantum and classical protocols and their success probabilities based on the function's noise stability.

Contribution

It extends the concept of RACs to Boolean functions, providing protocols and bounds for quantum and classical versions with various resources.

Findings

Quantum protocols have limited advantage over classical ones.

Success probability linked to Boolean function's noise stability.

Upper bounds match achievable success probabilities up to a constant.

Abstract

An $n\overset{p}{\mapsto}m$ random access code (RAC) is an encoding of $n$ bits into $m$ bits such that any initial bit can be recovered with probability at least $p$, while in a quantum RAC (QRAC), the $n$ bits are encoded into $m$ qubits. Since its proposal, the idea of RACs was generalized in many different ways, e.g. allowing the use of shared entanglement (called entanglement-assisted random access code, or simply EARAC) or recovering multiple bits instead of one. In this paper we generalize the idea of RACs to recovering the value of a given Boolean function $f$ on any subset of fixed size of the initial bits, which we call $f$-random access codes. We study and give protocols for $f$-random access codes with classical ($f$-RAC) and quantum ($f$-QRAC) encoding, together with many different resources, e.g. private or shared randomness, shared entanglement ($f$-EARAC) and Popescu-Rohrlich boxes ($f$-PRRAC). The success probability of our protocols is characterized by the \emph{noise stability} of the Boolean function $f$. Moreover, we give an \emph{upper bound} on the success probability of any $f$-QRAC with shared randomness that matches its success probability up to a multiplicative constant (and $f$-RACs by extension), meaning that quantum protocols can only achieve a limited advantage over their classical counterparts.