Abstract
Space division multiplexing based on multicore fibers (MCFs) is an optimum candidate to further increase the data bandwidth in optical communications, and its interest for spatial high-dimensional quantum cryptography has increased in the last few years. However, the main shortcoming lies in the appearance of phases and polarization acquired independently in each spatial mode after a long propagation, which prevents implementing efficient quantum key distribution (QKD) protocols with spatial optical modes. In this work, we propose a method for achieving phase, polarization, and time delay autocompensating for $ N $-dimensional QKD in MCFs by using strong coherent states coming from the Bob system. These coherent states make $ N $ trips between Alice and Bob and undergo $ N $ suitable optical transformations before Alice attenuates such states for producing 1-qudit states. Likewise, passive random-projective-measurement integrated devices are presented as well, in order to measure 1-qudit states. Finally, we analyze the behavior of the system under a cryptoghraphic attack, such as, e.g., the phase-remapping attack, in order to assess the strength of our system.
© 2019 Optical Society of America
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