Quantum Optical state comparison Amplifier enhanced by the feedforward mechanism

Amplifying signals is an essential task in many applications such as long distance communications. Because propagation of optical signals in a lossy medium such as optical fibers degrades the signal properties. Although any deterministic amplifying quantum optical systems introduce quantum additive noises which influence the quality of signal to noise ratio, non-deterministic noiseless linear amplifiers (NLA) can overcome this flaw. Weak coherent signals can be amplified by state comparison amplifiers which stand in the category of NLA. These linear amplifiers, which require no quantum resources, are based on some post selections of the output which depend on some specific conditioning detection outcomes. We enhance the performance of the state comparison amplifiers utilizing a feed forward scheme. The output fidelity and success probability of the amplified signal are boosted. Realization of the feedforward assisted state comparison amplifiers are discussed and analyzed.