Quantum information processing has a host of applications, including quantum key distribution and quantum computing as some of the most prominent. In all of these applications, sensing and control are needed in order to maintain the fidelity of quantum information. In quantum sensors, information stored in quantum mechanical systems is extracted and put to use, either in subsequent control signals, or in general information processing applications. Some famous examples of quantum sensors include atomic clocks, cold atom interferometers, or Bose-Einstein condensates used in gravitometers, accelerometers, etc. Some of the original proposals for quantum sensors involved optical fields. In particular, sensors that exploit continuously variable degrees of freedom have been of interest since the discovery of quantum noise reduction. One of the first examples proposed by Caves is the use quantum noise reduction to achieve interferometric sensitivity in the quantum regime. Advanced LIGO is an example of an upcoming application. In addition to LIGO, in recent years continuous variables have seen renewed interest. In this talk we will discuss quantum sensors and their applications with a focus on the sensors developed at ORNL. We use quantum noise reduction to produce sub-shot-noise limited sensing devices, particularly in quantum plasmonic sensors and displacement sensors using MEMS cantilevers. Some applications for these devices include trace detection or quantum information applications, such as removing bias from QRNGs through adaptive control. We will also discuss other sensing types that use both discrete and continuous variables, such as quantum compressive imaging, and single photon detection applications.