A communication linker includes: a classical encoder; an optical transmitter; a receiver; a local oscillator in communication with the receiver and that: receives a feedback signal; and produces a displacement frequency, based on the feedback signal; a single photon detector in communication with the receiver and that: receives an optical signal from the receiver; and produces a single photon detector signal, based on the optical signal; a signal processor in communication with the single photon detector and that: receives the single photon detector signal from the single photon detector; produces the feedback signal, based on the single photon detector signal; and produces a decoded signal, based on the single photon detector signal, the decoded signal comprising a frequency of the feedback signal.
The US has the leading optical communication industry and one of the largest telecommunication markets. Our invention directly improves the underlying technology of the telecommunication infrastructure.
Quantum Coherent Frequency Shift Keying (CFSK) receiver is a device that determines the frequency of the input electromagnetic signal given a pre-determined set of accepted frequencies (the alphabet). This device replaces a traditional receiver in a digital communications channel.
Traditionally, the minimum discrimination error probability is given by the shot noise in a channel and is called "standard quantum limit" (SQL). Our device allows for a much lower discrimination error. It enhances discrimination accuracy via quantum displacement measurements in a frequency-phase space (prior quantum receivers use displacement in amplitude-phase space leading to a much larger error rates for the same transmitted powers).
Benefits include: works with any optical communication channel (fiber, free space); fully compatible with the existing global fiber network; increases the amplification-free range; reduces transmitter power requirements; May be used to reduce frequency band with respect to classical protocols; compatible with currently-used alphabet sizes; and power-per-bit requirements do not increase with the alphabet size.