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Figure 6 | EPJ Quantum Technology

Figure 6

From: Transmission estimation at the quantum Cramér-Rao bound with macroscopic quantum light

Figure 6

Schematic of a basic spectrum analyzer. For a given input I, the spectrum analyzer splits the signal into two channels and mixes each of the resulting signals with an electronic local oscillator (LO). The LOs used for the two channels are 90° out of phase to obtain the in phase and out of phase components. After mixing with the LO, the resulting signal in each channel is passed through a low pass filter, which represents the RBW filter of the spectrum analyzer, and then squared. Finally, the signals from both channels are summed to obtain the output. An additional filter, the video bandwidth filter, can be used on the output to reduce the fluctuations on the noise measurements. This filter, however, does not affect the mean value of the measured noise, and as a result it is not considered given that it does not play a role in our results.

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