What is Q clearance?

Q clearance is a type of security clearance offered by the United States Department of Energy. It is functionally similar to the Top Secret clearance granted in other areas—and can generally be used as such—but also provides access authorization to restricted data and special nuclear material. The federal government primarily offers this clearance to outside contractors who need access to specific sites, though it may also be necessary for some positions within the Department of Energy and the military. Q clearance is the highest type of clearance given to contractors and often involves things like armed security escorts—or providing said escorts—when accessing certain types of information.