Interstellar communication. V. Introduction to photon information efficiency (in bits per photon)

TL;DR

This paper explores the theoretical limits of how much information a single photon can carry, considering various encoding modes, noise, and losses, to optimize interstellar communication.

Contribution

It introduces a framework for calculating the maximum bits per photon based on encoding modes, noise, and losses, advancing understanding of photon information efficiency.

Findings

Multiple bits per photon can be encoded using time, energy, and polarization modes.

Maximum information per photon depends on noise levels and system losses.

Provides a method to estimate photon information capacity in practical scenarios.

Abstract

How many bits of information can a single photon carry? Intuition says "one", but this is incorrect. With an alphabet based on the photon's time of arrival, energy, and polarization, several bits can be encoded. In this introduction to photon information efficiency, we explain how to calculate the maximum number of bits per photon depending on the number of encoding modes, noise, and losses.