Any quantum device that amplifies coherent states of a field while preserving their phase generates noise. A nonlinear, phase-invariant amplifier may generate less noise, over a range of input field strengths, than any linear amplifier with the same amplification. We present explicit examples of such nonlinear amplifiers and derive lower bounds on the noise generated by a nonlinear, phase-invariant quantum amplifier.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics