Centre for Development of Telematics

Roshan Lal Sharma

Vivek Kumar

Atul Kumar Gupta

Prashant Kumar Rathore

Prasanta Halder

The present disclosure relates to the field Quantum Key distribution (QKD) and discloses an apparatus () and method () for adjusting the phase modulator's modulating signal time reference in a phase-based QKD system. The QKD system comprises a pulse generator () that generates optical pulses and a phase modulator () that modulates the phase of each of the pulses. The apparatus () comprises abeam splitter/tap (), a 1-bit delay interferometer (), two photodetectors (), and a processing device (). The splitter feeds the phase modulated optical pulses to the interferometer (). Two photo detectors are connected to the constructive and destructive output legs () of the interferometer (). The photo detectors' output are then converted to digital signals and fed to the processing device (). The processing device () measures the average power at both the legs of the interferometer () to detect delay between optical signal and modulating signal and adjusts the delay to accurately align the phase modulator () with the pulse generator ().

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New Delhi, India

Roshan Lal Sharma