Principle of Quantum Key Distribution on an Optical Fiber Based on Time Shifts of TB Qubits

Abstract

The possibility of the physical realization of a quantum key distribution scheme in an optical-fiber communication channel based on time coding of two- and three-level single-photon quantum states is demonstrated. It is proposed to employ shifts of TB qubits (time-bin qubits) as protected code combinations, transmitted over a quantum channel, and for registering individual photons – the corresponding qutrits prepared in unbalanced Mach–Zehnder interferometers. The possibility of enhancing the level of protection of the code combinations as a result of taking into account information about qubit basis states and their statistics is indicated. A computer model of the time coding of TB qubits based on the BB84 protocol is developed, and results of calculations confirming the realizability of the indicated principle are presented.