Figure 2: Conductance of single and paired collimators.

(a) Conductance of collimator measured in a three terminal configuration: S4 is current-biased, F4 is grounded and all remaining terminals are measured with a single current amplifier. The measured conductance (blue) scales as (black dotted line), qualitatively agreeing with ballistic conduction of bulk graphene. Numerical solutions to the 2D Dirac equation (red dots) account well for low-density effects associated with diffraction. (b) Conductance measurements through angularly sensitive collectors. Current is collected at F3+S3 (red), S3 (blue) and S1 (black) with all remaining contacts grounded. F3+S3 has a broad background due to diffuse edge scattering and imperfect ohmic contacts. S3 has a FWHM of 8.5° due to double collimation and has minimal diffuse background. The peak height of S3 indicates nearly perfect ballistic transmission.