Fig. 4: Measured polarization visibility fringes by varying Bob’s phase.

The green area represents a visibility of greater than 81%, representing the limit for QKD protocols. a Core pair 1-1′ HV Basis, b Core pair 1-1′ DA Basis, (c) Core pair 2-2’s HV Basis, (d) Core pair 2-2′ DA Basis. At multiples of 2π the polarization visibility drops. This stems from the fact that destructive interference for the coincidences occurs, thus fewer coincidences are measured. For each data point the integration time was 30 s. We assumed Poissonian statistics, note that the errors are smaller than the data points.