  In this work we investigate quantum-enhanced target detection in the presence
of large background noise using multidimensional quantum correlations between
photon pairs generated through spontaneous parametric down-conversion. Until
now similar experiments have only utilized one of the photon pairs' many
degrees of freedom such as temporal correlations and photon number
correlations. Here, we utilized both temporal and spectral correlations of the
photon pairs and achieved over an order of magnitude reduction to the
background noise and in turn significant reduction to data acquisition time
when compared to utilizing only temporal modes. We believe this work represents
an important step in realizing a practical, real-time quantum-enhanced target
detection system. The demonstrated technique will also be of importance in many
other quantum sensing applications and quantum communications.
