Quantum-Limited Symbol-Blind Channel Estimation for Coherent State Discrimination

Residual dispersion breaks temporal-mode matching in photon-starved coherent links. For equiprobable $M$-ary PSK coherent states in a known spectral mode, with unknown symbols and carrier phase, we establish the quantum limit for blind joint estimation of group delay and second-order dispersion: after eliminating the common phase, it is $4N_s\mathbf{C}$, set by the covariance of the centered generators alone. A multi-output quantum pulse gate with photon-number-resolving detection locally attains it and supports reception below the standard quantum limit under turbulent fading.

Panoramic single-pixel imaging with megapixel resolution based on rotational subdivision

Single-pixel imaging (SPI) using a single-pixel detector is an unconventional imaging method, which has great application prospects in many fields to realize high-performance imaging. In especial, the recent proposed catadioptric panoramic ghost imaging (CPGI) extends the application potential of SPI to high-performance imaging at a wide field of view (FOV) with recent growing demands. However, the resolution of CPGI is limited by hardware parameters of the digital micromirror device (DMD), which may not meet ultrahigh-resolution panoramic imaging needs that require detailed information. Therefore, to overcome the resolution limitation of CPGI, we propose a panoramic SPI based on rotational subdivision (RSPSI). The key of the proposed RSPSI is to obtain the entire panoramic scene by the rotation-scanning with a rotating mirror tilted 45{\deg}, so that one single pattern that only covers one sub-Fov with a small FOV can complete a uninterrupted modulation on the entire panoramic FOV during a once-through pattern projection. Then, based on temporal resolution subdivision, images sequence of sub-Fovs subdivided from the entire panoramic FOV can be reconstructed with pixels-level or even subpixels-level horizontal shifting adjacently. Experimental results using a proof-of-concept setup show that the panoramic image can be obtained with 10428*543 of 5,662,404 pixels, which is more than 9.6 times higher than the resolution limit of the CPGI using the same DMD. To our best knowledge, the RSPSI is the first to achieve a megapixel resolution via SPI, which can provide potential applications in fields requiring the imaging with ultrahigh-resolution and wide FOV.