Q Factor

The quality factor, also known as the "Q factor", "Q value", or just "Q", is a dimensionless parameter that characterizes the energy loss of a resonating cavity with respect to the energy stored in the cavity. See the Wikipedia entry for a more general and detailed description. There are multiple, incompatible ways to measure this parameter, and there has been considerable debate on the NSF forums as to which is most appropriate for the EM Drive. Regardless, publicized experiments have so far reported the unloaded Q factor, even though the loaded Q factor is generally considered the standard technique outside of the EM Drive research community.Template:Citation needed

There is no standard notation to distinguish between the method used. We use "Q_l" to explicitly denote the loaded Q factor and "Q_u" to denote the unloaded Q factor.