When it became known that quantum computers could break the RSA (named for its creators - Rivest, Shamir, and Adleman) encryption algorithm within a polynomial-time, quantum cryptography began to be actively studied. Other classical cryptographic algorithms are only secure when malicious users do not have computational power enough to break security within a practical amount of time. Recently, many quantum authentication protocols sharing quantum entangled particles between communicators have been proposed, providing unconditional security. An issue caused by sharing quantum entangled particles is that it may not be simple to apply these protocols to authenticate a specific user in a group of many users. We propose an authentication protocol using quantum superposition states instead of quantum entangled particles. Our protocol can be implemented with the current technologies we introduce in this paper.

This article addresses the development of and recent advances in the rapidly growing field of optical pattern recognition. In optical pattern recognition there are two basic approaches; namely, matched filtering and associative memories. The first employs optical correlator architectures and the latter uses optical neural networks (NNs). This paper reviews various types of optical correlators and NNs applied to real-time pattern recognition and autonomous tracking. Techniques of scale and rotational invariant filtering are also given. Recent approaches using wavelet transform filtering, phase only filtering, high capacity composite filters and phase representation for improvement in pattern discrimination are also provided.

A demonstration of the capabilities and limitations of an optical correlator in a realistic environment has been undertaken. The testing is divided into several phases from laboratory-type data gathering to a fully functional helicopter-delivered demonstration missile. The basic research performed has led to three fully fieldable test units which have proved to be rugged and dependable under normal test range conditions. The units were transportable and required no realignment of the optics. Two of the test systems were modular in construction while the third was a 'solid optic' design having optical paths and components contained within a solid glass construction.>