probe light, environmental noise is not correlated or entangled with the reference light.

One of the most prominent approaches to utilize such quantum advantages is *quantum illumination*, which utilizes the entanglement between the reference and probe light to significantly boost the target detection sensitivity beyond the classical limit [@lloyd2008enhanced]. Recent work suggests that such benefits of entanglement could even survive through an extremely lossy and noisy target detection channel [@Zhang:2015]. However, in order to profit from such entanglement benefit, a significant level of complexity in the instrumentation, including phase-sensitive joint detection[^2], is essential. For example, the implementation in [@Zhang:2015] requires sub-wavelength-level stabilization of optical phases between the probe and reference light, which is far from practical if the target distance is unknown or fluctuating. As such, formidable challenges lie ahead on the route to harvesting the entanglement advantages. An alternative strategy to enhance the target detection performance while mitigating the complexity of quantum illumination is to only use classical correlations that exist in the non-classical twin beams. Unlike entanglement, the measurement of correlation only entails independent measurements of the probe and reference light and is therefore much more feasible for practical implementation. The key aspect of correlation enhanced target detection 