Signal-to-noise ratio in squeezed-light laser radar

Abstract

The formalism for computing the signal-to-noise ratio (SNR) for laser radar is reviewed and applied to the tasks of target detection, direction-finding, and phase change estimation with squeezed light. The SNR for heterodyne detection of coherent light using a squeezed local oscillator is lower than that obtained using a coherent local oscillator. This is true for target detection, for phase estimation, and for direction-finding with a split detector. Squeezing the local oscillator also lowers SNR in balanced homodyne and heterodyne detection of coherent light. Loss places an upper bound on the improvement that squeezing can bring to direct-detection SNR.

A Fundamental Upper Bound for Signal to Noise Ratio of Quantum Detectors

“…In addition, inevitable noises happen due to quantum fluctuations of the observables and may dominate in quantum regime. Especially in quantum optics, exploration of quantum SNR has been performed in earlier study for individual subjects, including squeezed states [1][2] [3], weak measurements [4][5] [6], multimode spatial entanglement detection [7], electron-multiplying CCD camera [8], heralded linear amplifier [9], and correlation plenoptic imaging [10]. In this paper, we provide a universal upper bound of quantum SNR for arbitrary quantum detection with trace-class operators.…”