Theory and Applications of Observability of Classical And Quantized Radiation Fields

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9900246ZiolkowskiIn the classical theory of electromagnetic radiation, there are certain localized charge-current distributions which do not radiate. Such sources, commonly referred to as nonradiating sources, generate fields which are themselves confined within the region of localization of the source [1]. Investigations on nonradiating sources have addressed both scalar [2, 3, 4, 5] and electromagnetic sources [1, 6, 7, 8] as well as both deterministic and random sources [9, 10, 11]. The question arises whether nonradiating sources have (or not) a counterpart in the quantum theory. Surprisingly, this fundamental question does not appear to have been addressed before. The main goal of the proposed program of research is to develop a new theory of nonradiating sources for both classical and quantized fields and to address potential and concrete applications of the developed theory. Specific theoretical and applicational aims of the projected research are described below.We propose to deal (classically and quantum-electrodynamically) with both monochromatic and transient (e.g., pulsed) sources and fields. The classical component of the proposed research will focus on developing new tools for analysis and synthesis of nonradiating sources in the time and frequency domains. The objectives of this portion of the project include: 1.) developing a new inverse source and nonradiating source theory in the time domain, 2.) developing complete sets of vector functions to represent monochromatic as well as transient nonradiating sources of compact support, and 3.) exploring fundamental (and potentially practical) connections between nonradiating sources and other wave objects, such as the scalar and vector potentials and minimum energy solutions to the inverse source problem of electromagnetics. The proposed work along those lines is expected to parallel (and generalize) previous work by the proposers for scalar sources and fields. That work includes new formulations of the inverse source problem [12] as well as new descriptions of nonradiating sources [13] and of their connection with minimum energy sources and perfect radiators [14]. The theoretical component of the outlined effort is expected to give light, also, into the nature of nonradiating sources in the quantum theory, thereby contributing to a more fundamental understanding of the observability of sources and scatterers and their fields. The purpose is to answer conclusively the question of existence of nonradiating sources in the quantum theory. Furthermore, the developed theory could have impact in fundamental aspects of quantum theory and, in particular, in a controversial, not fully-understood, quantum-mechanical phenomenon, namely, the Aharonov-Bohm effect, wherein charged particles can be influenced by classical, localized sources and their fields in regions where the fields (and therefore the forces on the particles) vanish [15, 16]. Thus, we propose also to examine the connection between the Aharonov-Bohm effect and the observability of quantised radiation fields.The developed theory could, potentially, set the stage for novel communication schemes (based on nonra-diating sources), as well as new techniques for interrogation of sources and scatterers (in both hardware and algorithms). The latter aspects constitute the focus of the second part of the proposed research, aimed at ap-plications. The applications of interest rely on the possibility of sensing via quantum-mechanical experiments (i.e., new field-sensing devices) certain features of a source (e.g., information) which would be otherwise (i.e., via classical sensors (antennas)) inherently unobservable. Thus, system-level designs for new field-sensing devices based, e.g., on the Aharonov-Bohm effect and/or other unconventional, quantum-mechanical field-particle interaction effects, are also potential outcomes of the proposed effort. Of particular relevance to communication technologies is the possibility of generating fields that are confined (localized), classically, within the source's region of support (antenna's structure), but that are not such quantum-mechanically. The latter possibility opens, potentially, a window for efficient, secured transmission of field-observables (sig-halS), generated by conventional sources (antennas) but sensed via unconventional, quantum-electrodynamic field-sensors. In this way, one would obtain, e.g., added flexibility (not available in antenna-to-antenna communication) for transmitting either all or part of the to-be-transmitted information via a "channel" that opens only to quantum-electrodynamic field-sensors while being unavailable to traditional field-sensors (receiving antennas). In summary, the main areas of technological impact - to be explored as part of the proposed effort - are 1.) novel field-sensing devices, 2.) new communications technology and 3.) new algorithms and hardware for interrogation of sources and scatterers.***