A doubly exponential upper bound on noisy EPR states for binary games

TL;DR

This paper establishes a doubly exponential upper bound on the number of noisy EPR states needed for players to approximate the value of binary mono-state entangled games, advancing understanding in quantum complexity and nonlocal games.

Contribution

It introduces a doubly exponential bound for noisy EPR states in mono-state binary games and develops new Fourier analysis techniques on matrix spaces.

Findings

Doubly exponential upper bound on noisy EPR states for game approximation

New Fourier analysis methods on matrix spaces

Progress towards the decidability of MIP* complexity class

Abstract

This paper initiates the study of a class of entangled games, mono-state games, denoted by $(G,\psi)$, where $G$ is a two-player one-round game and $\psi$ is a bipartite state independent of the game $G$. In the mono-state game $(G,\psi)$, the players are only allowed to share arbitrary copies of $\psi$. This paper provides a doubly exponential upper bound on the copies of $\psi$ for the players to approximate the value of the game to an arbitrarily small constant precision for any mono-state binary game $(G,\psi)$, if $\psi$ is a noisy EPR state, which is a two-qubit state with completely mixed states as marginals and maximal correlation less than $1$. In particular, it includes $(1-\epsilon)|\Psi\rangle\langle\Psi|+\epsilon\frac{I_2}{2}\otimes\frac{I_2}{2}$, an EPR state with an arbitrary depolarizing noise $\epsilon>0$.The structure of the proofs is built the recent framework about the decidability of the non-interactive simulation of joint distributions, which is completely different from all previous optimization-based approaches or "Tsirelson's problem"-based approaches. This paper develops a series of new techniques about the Fourier analysis on matrix spaces and proves a quantum invariance principle and a hypercontractive inequality of random operators. This novel approach provides a new angle to study the decidability of the complexity class MIP$^*$, a longstanding open problem in quantum complexity theory.