Imperfect unambiguous state discrimination: practical case study for future networks

We thoroughly investigate the amplitude and phase fluctuations affect the performance of USD. We provide a comprehensive analysis insights into the limitations of USD in practical scenarios, making the findings relevant for real-world applications. By introducing a set of positive operator value measurements, we suggest a USD measurement for discriminating between to coherent states with the same amplitude and different phases. The model develops by setting orthogonal states, i.e., a superposition of the potential outputs, to discriminate two phases. However, as during the preparation of this signal from the laser beam, unavoidable errors occur which transform the output coherent signals into imperfect input signals. This imperfection can be modeled as fluctuation errors i.e., amplitude and phase fluctuations. We apply this model by considering the noise and study the impact of both the states on the USD measurement. This results in an error in the measurement making "perfect" USD to "imperfect" USD. We further stimulate and analyse the impact of both the errors and found out that the proposed method works for a certain window of intensity of light. It doesn’t provide us with desired results for lower amplitudes of light while for higher amplitudes the error in the measurement becomes too large making the measurement meaningless. This have implications on low-energy transmitters and practical implementations of USD, thereby, we address a significant gap in the literature regarding the applicability of quantum state discrimination methods in future quantum communication systems.