Abstract: A method for down-converting an RF signal is described that optically phase modulates an RF signal onto an optical carrier then applies an RF local oscillator (LO) phase modulation which down-converts the RF signal to an intermediate frequency after appropriate optical signal processing and optical-to-electrical photo-detection. The LO phase modulator is constructed such that a common hot electrode is shared among more than one optical mode, where an optical mode can be separate waveguides or optical wavelengths. The relative phase of the LO frequency applied to each optical mode can be different between the different optical modes. The resulting down-converted photo-detected signals of different LO-phase can be processed to reduce noise. A single LO phase modulator can down-convert multiple RF signals carried by multiple optical wavelengths, and a harmonic generation stage with multi-phase-matching peaks can be used to linearize each RF signal.

Abstract: Apparatus and method for producing quantum entangled signal and idler photon pairs is provided. The apparatus makes use of a nonlinear optical fiber to generate the entangled photons. The use of an external broad band light source for alignment of any downstream measurement apparatuses is disclosed. One or more polarized output signals can be generated at both the signal and idler wavelengths using the alignment source, allowing the downstream measurement apparatuses to be aligned using classical light. Multiple signal and idler wavelengths can be generated and aligned using such a system.

Abstract: Apparatus and method for a secure communication network using AlphaEta quantum encryption is provided. A polarization insensitive optical receiver based on a 90 degrees hybrid coupler is used for the detection and digitization of optically encrypted signals. Once digitized, such signals can be decrypted, stored, or re-transmitted over arbitrary media such as using RF wireless means. Alternatively, the signal can be generated directly for transmission over RF wireless nodes. The system may include nodes for retransmitting the signal without decrypting it, allowing for secure communication among specific users.

Abstract: The present invention provides an apparatus and method for producing entangled photon pairs via four-wave mixing in optical fiber. The source of entangled photons is designed to be stable with no manual alignment. This is accomplished with proper system design using polarization maintaining fibers or polarization controllers with feedback control. The source may contain a method of switching the output from an unpolarized entangled state to a polarized state, where the polarized state can be used to more easily align subsequent photon measurement systems to the proper configuration for measuring the unpolarized entangled state. The invention further provides a means to engineer the apparatus, including the use of a periodic filter common to both entangled pairs, such that the wavelength spacing between the pairs can be optimized such that multiple pairs can be generated with reduced adverse influence from Raman scattering.

Abstract: Techniques to bolster the security of an AlphaEta cryptosystem using spectral phase encoding. In one aspect, a spatial light modulator (SLM) is used to change the spectral code (spectral phase) of each optical bit in response to the output of an extended key generator based on a cryptographic algorithm. In other aspects, additional time and polarization modulations are used to maintain high security levels as well as good performance levels. Such methods are combined with traditional key generation methods such as key-distribution centers or one-way mathematical algorithms to bolster the security of traditional key generation as well.