Fig. 2: Theoretical limits on quantum efficiency.
From: Beyond the standard quantum limit for parametric amplification of broadband signals
Limit ηql of the quantum efficiency η as a function of the signal bandwidth bs for a varying detuning Δ at a fixed measurement bandwidth B/2π = 30 kHz and b for varying measurement bandwidth B at a fixed detuning Δ/2π = 37.5 kHz, according to Eq. (8). For bs ≥ b2, amplification with η = 1 is possible. The case bs ≤ B is only of technical interest and is discussed in the supplement (see Supplemental Material).
