Temporal SU(1,1) interferometer with broadband squeezed light injection

Temporal optics has attracted much attention due to its ability for lossless stretching of ultrafast temporal pulses. Concurrently, spatial SU(1,1) interferometers (SUIs) are widely utilized due to their high sensitivity to phase changes. Building on these concepts, we investigate a temporal SUI based on a temporal Fourier transform system, injecting broadband squeezed light for characterization. Our results show that the output spectral characteristics of the interferometer depend on the ratio of the focal group delay dispersion values of the two time lenses (defined as the scaling factor $M$) and the derivative of the applied phase. The scaling factor $M$ strongly influences both the bandwidth and the degree of squeezing in the output spectrum. Meanwhile, the phase derivative induces a frequency shift proportional to its magnitude. Furthermore, the output squeezed-state spectrum exhibits concentrated squeezing at both the center frequency and the shifted frequencies. As the scaling factor $M$ increases, the proportion of squeezing concentrated at the center frequency increases correspondingly. We also theoretically analyze and numerically calculate the phase sensitivity with respect to the phase derivative and the scaling factor $M$, under both lossless and lossy conditions. This temporal SUI architecture opens new avenues for the control of nonclassical fields in the time-frequency domain and quantum information processing applications.