The role of photon-number pulses in the operation of a simple light diode

TL;DR

This paper investigates a simple optical diode model using two atoms in a waveguide, clarifying how photon-number pulses influence rectification, especially highlighting rectification effects for single-photon states outside the infinite pulse limit.

Contribution

The study demonstrates that rectification depends solely on Fock state behavior and reveals single-photon rectification when finite pulse lengths are considered.

Findings

Rectification depends only on Fock state properties.

Single-photon rectification occurs with finite pulse lengths.

Coherences across Fock bases are irrelevant for rectification.

Abstract

One of the challenges faced by optical platforms for quantum technologies is the implementation of (ultimately) a transistor. The functionality that is hard to achieve is rectification: having the beam propagating in one direction transmitted, the other reflected. Here we take up a simple model of such a rectifying device, a.k.a.~optical diode, consisting of two atoms with different detuning interacting with light in a one-dimensional waveguide. In previous studies, it was found that high rectifying efficiencies can be achieved with coherent states, while it was claimed that the device cannot rectify single-photon Fock states. In this paper, we clarify the functioning of this diode. Notably, we show that coherences across the Fock bases in the input state do not play any role, and thence the rectifying properties of the device depend only on its behavior on the Fock states. In the process, we show that some single-photon rectification is predicted when the limit of infinitely-long pulses is not taken.