independent modes, which is much greater than the $\sim 10^6$ accessible to the Cosmic Microwave Background, in principle unlocking a far greater portion of the available information in our observable Universe [@loeb_and_zaldarriaga2004; @mao_et_al2008; @tegmark_and_zaldarriaga2009; @ma_and_scott2016; @scott_et_al2016].

A large number of intensity mapping experiments are in operation, and more have been proposed. Post-reionization neutral hydrogen $21\,\textrm{cm}$ intensity mapping is being conducted by the Canadian Hydrogen Intensity Mapping Experiment [@bandura_et_al2014], the Green Bank Telescope [@masui_et_al2013], Tianlai telescope [@chen_et_al2012], Baryon Acoustic Oscillations from Integrated Neutral Gas Observations project [@battye_et_al2013], Hydrogen Intensity and Real-time Analysis eXperiment [@newburgh_et_al2016], and BAORadio [@ansari_et_al2012]. These experiments use neutral hydrogen as a tracer of the large scale density field, with a primary scientific goal of constraining dark energy via measurements of the baryon acoustic oscillation feature from $0 < z < 4$ [@wyithe_et_al2008; @chang_et_al2008; @pober_et_al2013a]. At $z \sim 2$ to $3.5$, data from the Sloan Digital Sky Survey have been used for Ly $\alpha$ intensity mapping [@croft_et_al2016]. Other experiments such as the CO Power Spectrum Survey [@keating_et_al2015; @keating_et_al2016] and the CO Mapping Array Pathfinder [@li_et_al2016] use CO as a tracer of molecular gas in the epoch of galaxy formation at roughly $z \sim 2$ to $3$. Using \[CII\] instead 