Quantum Model for Electro-Optical Phase Modulation

TL;DR

This paper develops a quantum model for electro-optical phase modulation, providing a unitary operator framework that aligns with classical results for optical frequencies and extends to multitone RF modulation.

Contribution

It introduces a novel quantum scattering operator for phase modulation that is physically consistent and applicable to complex quantum information systems.

Findings

The model is consistent with classical descriptions at optical frequencies.

A unitary operator for phase modulation over positive-frequency modes is constructed.

The approach effectively characterizes multitone radiofrequency modulation of optical signals.

Abstract

We present a detailed analysis of the quantum description of electro-optical phase modulation. The results define a black-box type model for this device which may be especially useful in the engineering steps leading to the design of complex quantum information systems incorporating one or more of these devices. By constructing an explicit representation of the phase modulation scattering operator, it is shown that an approach based entirely on its classical description leads to unphysical modes associated to non-positive frequencies. After modifying this operator, phase modulation is described, for the first time to the best of our knowledge, in terms of a unitary scattering operator defined over positive-frequency modes. The modifications introduced by in the process of sideband generation by phase modulation are shown to be not significant when the radiation belongs to optical bands, thus being consistent with the classical description. Finally, the model is employed to characterize the important case of multitone radiofrequency modulation of an optical signal.