Photocount statistics of broadband squeezed states
Аннотация
Consider a photodetector characterized by two bandwidths: (i) an optical bandwidth over which it has nearly unity quantum efficiency and (ii) a much smaller electronic bandwidth, the bandwidth over which it produces beats between different frequencies. Direct onto the photodetector a light beam which is the superposition of two parts: (i) an intense, nearly monochromatic carrier wave at some carrier frequency and (ii) a squeezed state with zero mean field, which is squeezed in the broadband (multimode) sense (correlation between frequencies located symmetrically above and below the carrier frequency) within some bandwidth about the carrier. The standard statements are that, if the squeezed quadrature is in phase with the carrier (amplitude-modulation squeezing), one will see sub-Poissonian photocount statistics, and if the squeezed quadrature is out of phase with the carrier (phase-modulation squeezing), one will see super-Poissonian statistics. Bandwidth considerations impact these statements in the following way: the only part of the squeezing that is relevant for decreasing or increasing the counting noise is that part that lies within an electronic bandwidth of the carrier frequency; to see the maximum decrease or increase, one must squeeze over the entire electronic bandwidth. These conclusions require modification if the carrier wave is not sufficiently intense.