Exploiting Faraday Rotation to Jam Quantum Key Distribution via Polarized Photons

Abstract

Quantum key distribution (QKD) involving polarized photons could be vulnerable to a jamming attack, in which a third party applies an external magnetic field to rotate the plane of polarization of photons headed toward one of the two intended recipients. Sufficiently large Faraday rotation of one of the polarized beams would prevent Alice and Bob from establishing a secure quantum channel. We investigate requirements to induce such rotation both for free-space transmission and for transmission via optical fiber, and find reasonable ranges of parameters in which a jamming attack could be successful against fiber-based QKD, even for systems that implement automated recalibration for polarization-frame alignment.