Analysis and design of secure quantum communication systems utilizing electromagnetic Schrodinger coherent states

Abstract

We develop a general mathematical formalism and computational method suitable for analyzing the performance of quantum communication systems utilizing coherent radiation states (Schrodinger states). The key motivation is to demonstrate how the analysis and design of quantum communication systems may benefit from the integration of the physical structure (here, the optical quantum coherent state) with the quantum signal processing aspects (here, quantum estimation and prediction theory). As an application, we show how the quantum-electromagnetic signature of optical radiation emitted by quantum antennas, the Schrodinger's coherent state structure, may be exploited to jointly design the transmitter and receiver of a K-ary digital communication link. We present a concrete example comprised of a quantum quadrature-amplitude modulation (QAM) system (with K = 64), including a complete description of the required general design principles developed from quantum mechanics and the quantum antenna's radiated coherent state structure. The simulation results illustrate improvement in spectral efficiency due to the use of K = 64 over smaller values of K. We also compare the quantum antenna-based link performance with classical QAM utilizing classical antenna-based communication systems and report superiority of the quantum link over the classical version. To provide for security protection, our system is equipped with a quantum encryption protocol for quantum key distribution, and a demonstration of the complete quantum QAM system with encryption is presented. The main message of the article is the fruitfulness of incorporating a multidisciplinary approach to our thinking about electromagnetic wireless systems through the joint deployment of electromagnetic, quantum, and communication theories in the design and development process of current and future advanced technologies.

Fundamental Spacetime Representations of Quantum Antenna Systems

“…We also further note that the field modal expansion (A26) is intrinsically Lorentz invariant, even though the spectral integration performed there is carried with respect to the non-Lorentz invariant volume measure d 3 x because the standard method of normalizing factor has been already employed in our formulation. 14 In other words, the spacetime q-antenna theory developed here is fully relativistic. A breakdown of relativistic invariance, as exemplified by choices of spatiotemporal decomposition (slicing) of the source or receiver regions D s,r , e.g., as in (3), can be introduced later as an external restriction enforced by hand to simplify the calculations and the presentation.…”

“…Example 1 (Classical current source). In order to appreciate why the presence of joint source functions signifies interactions, let us consider the well-known case of a classical current source (i.e., the backreaction of the quantum field on the source is ignored) when such source function J(x) is inserted into the Lagrangian of quantum field theory [14,62].…”

“…13 For additional information on the physical processes modeled by a Klein-Gordon quantum field, see [74,75]. 14 For a more detailed discussion of relativistic QFT, see [38,76]. 15 The generation of φ(x) itself is not treated here for simplicity.…”

“…Quantum antenna technology is a recent emerging subfield within the larger and more fluid research area often referred to as quantum engineering, quantum technologies, or just quantum information processing. In particular, and within this subfield, we find that the main intention behind the desire for developing a new "quantum antenna technology" is to serve the needs of current and future quantum communication systems [1][2][3][4], where information is transmitted using quantum states [5,6], regardless of whether digital data are encoded as classical bits or qbits [1,[7][8][9][10], with obvious applications to physical-layer security [11][12][13][14]. However, the peculiar system known as "the quantum antenna" may Foundations 2022, 2 252 also perform functions other than mere information transmission in wireless quantum links, for example, quantum tomography, quantum state estimation, biophotonics, sensing, molecular communications, space exploration, and other applications [13,[15][16][17][18][19][20][21][22][23][24][25][26].…”

Markovian Quantum Antenna Theory

“…The subject of quantum antennas enjoys a considerable range of existing and potential applications in various fields. In particular, these antenna types are not only capable of supporting functions pertinent to information transmission, processing, and reception in quantum telecommunication links [30], [31], but, moreover, a quantum antenna system may be used for a wide range of fundamentally different applications such as bio-sensing, photonic energy devices, quantum imaging and tomography, quantum control, and high-speed computing chip design, and others [9]- [17]. Such increase in the number of possible applications as seen in the quantum case is due to the enhanced universality and intrinsic richness of quantum structures when compared with the classical electromagnetic structure.…”