Figure 4: Effect of losses on the enhancement of signal-to-noise ratio.
From: Quantum metrology with parametric amplifier-based photon correlation interferometers
(a) Extra external loss; (b) extra internal loss on the both arms. The blue diamond points are the output noise level above the vacuum level; the black square points are the signal enhancement factor; the red triangle points are the signal-to-noise ratio enhancement factor. Solid curves in (a) are from equation (7) with BS0=7.5 dB and N0=3.2 dB. The solid lines in (b) are for visual guidance. At small losses, the SNR enhancement factor (red triangle) is less sensitive to the external losses than to internal losses. The size of the error bars is one s.d., derived from the data of the traces similar to the light blue and red traces in Fig. 2.
