Precision Tests of Parity Violation Over Cosmological Distances
  Recent measurements of the Cosmic Microwave Background $B$-mode polarization
power spectrum by the BICEP2 and POLARBEAR experiments have demonstrated new
precision tools for probing fundamental physics. Regardless of origin, the fact
that we can detect sub-$\mu$K CMB polarization represents a tremendous
technological breakthrough. Yet more information may be latent in the CMB's
polarization pattern. Because of its tensorial nature, CMB polarization may
also reveal parity-violating physics via a detection of cosmic polarization
rotation. Although current CMB polarimeters are sensitive enough to measure one
degree-level polarization rotation with $>5\sigma$ statistical significance,
they lack the ability to differentiate this effect from a systematic
instrumental polarization rotation. Here, we motivate the search for cosmic
polarization rotation from current CMB data as well as independent radio galaxy
and quasar polarization measurements. We argue that an improvement in
calibration accuracy would allow the precise measurement of parity- and
Lorentz-violating effects. We describe the CalSat space-based polarization
calibrator that will provide stringent control of systematic polarization angle
calibration uncertainties to $0.05^\circ$ -- an order of magnitude improvement
over current CMB polarization calibrators. CalSat-based calibration could be
used with current CMB polarimeters searching for $B$-mode polarization,
effectively turning them into probes of cosmic parity violation, i.e. without
the need to build dedicated instruments.
