# Entanglement-assisted communication in the absence of shared reference frame

## TL;DR

This paper investigates how entangled states can be used for parameter communication between parties without a shared reference frame, showing entanglement enhances information transfer.

## Contribution

It demonstrates that entangled two-qubit states have three invariant parameters useful for communication without shared reference frames, improving information gain over separable states.

## Key findings

- Entangled states have three invariant parameters for communication.
- Entanglement increases average information gain.
- Entanglement outperforms separable states in this context.

## Abstract

Alice wants to convey the value of a parameter to Bob with whom she does not share a reference frame. What physical object can she use for this task? Shall she encode this value into the angle between two physical vectors such as the angle between two spins? Can she benefit from using entanglement? We approach these questions here and show that an entangled state of two qubits has three parameters that are invariant under changes of the reference frame. We also calculate the average information gain, when each one of these parameters is used for communication. We compare our result with the special case of separable states and find that entanglement enhances the information gain.