IEEE - Aerospace and Electronic Systems - May 2022 - Tutorial XV - 68

Tutorial:
DOI. No. 10.1109/MAES.2021.3116323
Detecting a Target With Quantum Entanglement
Giacomo Sorelli , Laboratoire Kastler Brossel, 75252 Paris, France, and
DEMR ONERA, 91123, Palaiseau, France, and also Sorbonne Universite´ ,
75005 Paris, France
Nicolas Treps, Laboratoire Kastler Brossel, 75252 Paris, France
Frederic Grosshans, Sorbonne Universite, 75005 Paris, France
Fabrice Boust, DEMR ONERA, 91123 Palaiseau, France
Over the last decade, research activity has focused on the
use of quantum entanglement as a resource for remote
target detection, i.e., on the design of a quantum radar.
The literature on this subject uses tools of quantum optics
and quantum information theory, and therefore, results
are often obscure to radar engineers. This tutorial has
been written with the purpose of removing this obscurity.
As such, it contains a review of the main advances in
quantum radar literature accompanied by a thorough
introduction of the quantum optics background necessary
for its understanding.
INTRODUCTION
The idea that by interactingwith a quantum system an observer
could obtain information about another system completely
separated from the first one was first presented by Einstein,
Podolsky, and Rosen in their seminal paper in 1935 [1]. Later
that year, Schr€odinger called this phenomenon entanglement,
andsaidthatitisnot " one but rather the characteristic trait of
quantum mechanics " [2], [3]. Nowadays, almost 100 years
Authors' current address: G. Sorelli is with the Laboratoire
Kastler Brossel, Sorbonne Universite, ENS-Universit
e PSL, College de France, CNRSins, Paris F75252,
France, also with the Sorbonne Universite,
CNRS, LIP6, Paris F-75005, France, and also with the
DEMR, ONERA, Universite Paris Saclay, Palaiseau F75005,
France (e-mail: giacomo.sorelli@lkb.upmc.fr);
N. Treps is with the Laboratoire Kastler Brossel, Sorbonne
Universite, ENS-Universite PSL, College de
France, CNRSins, Paris F-75252, France (e-mail: nicolas.treps@upmc.fr);
F. Grosshans is with the Sorbonne
Universite, CNRS, LIP6, Paris F-75005, France (e-mail:
frederic.grosshans@lip6.fr); F. Boust is with the DEMR,
ONERA, Universite Paris Saclay, Palaiseau F-75005,
France (e-mail: fabrice.boust@onera.fr).
Manuscript received January 7, 2021, revised July 21,
2021; accepted July 21, 2021, and ready for publication
September 27, 2021.
Review handled by Dale Blair.
0885-8985/21/$26.00 ß 2021 IEEE
68
later, entanglement is not only considered a fundamental
aspect ofquantum theory, but also a precious resource for several
quantum information protocols such as quantum computing,
quantumcommunication, and quantum metrology.
Recently, many research activities have focused on the
use of entangled radiation in target detection, leading to
the study of quantum lidars and radars. The aim of this
review is to introduce these recent advances in the theory
of target detection using quantum radiation to readers with
no background in quantum optics, with a particular focus
on their applicability in realistic scenarios.
To achieve this goal, we will start from an historical overview
to give the reader an idea about how this subject
appeared and developed during the last decade in the realm of
quantum information. Then, before jumping into a quite
detailed description of the quantum target-detection protocol,
also known as quantum illumination (QI), we will introduce
some preliminary concepts. We will first present some basics
ofquantum optics, then we will discuss howto decide between
two hypotheses (target present/target absent) by distinguishing
different probability distributions (a subject that should be
familiar to radar engineers) and adapt these concepts to the
problem ofdiscriminating different quantum states.
After having set this background, we will discuss the
performances of QI and point out under which conditions
one can obtain a quantum advantage. We will also point
out the main practical limitations of these protocols, most
ofwhich were already reported in [4] and [5]. In particular,
we will see that a quantum advantage is possible only when
extremely low signal powers are employed, and therefore,
QI is ofvery little use for remote target detection.
We will conclude this review by giving a quick overview
ofthe state ofthe art ofquantum radar experiments. In particular,
we will discuss how, in most cases, these experiments are
unable to prove the quantumadvantage predicted by QI theory.
HISTORICAL OVERVIEW
The history of QI started in 2008, following two lines of
research. The works [6], [7] considered the radar problem
IEEE A&E SYSTEMS MAGAZINE
MAY 2022
https://orcid.org/0000-0003-2197-2768
IEEE - Aerospace and Electronic Systems - May 2022 - Tutorial XV

Table of Contents for the Digital Edition of IEEE - Aerospace and Electronic Systems - May 2022 - Tutorial XV
