**Universal Microwave Photonics Approach to Frequency-Coded Quantum Key Distribution Frequency-Coded Quantum Key Distribution**

**Universal Microwave Photonics Approach to** 

DOI: 10.5772/intechopen.71974

Oleg G. Morozov, Airat J. Sakhabutdinov, Gennady A. Morozov and Il'daris M. Gabdulkhakov Gennady A. Morozov and Il'daris M. Gabdulkhakov Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Oleg G. Morozov, Airat J. Sakhabutdinov,

http://dx.doi.org/10.5772/intechopen.71974

#### **Abstract**

Design principles of universal microwave photonics system (MPS) for quantum key distribution (QKD) with frequency coding are concerned. Its main modulation concept lies in single photon generation on sidebands of optical carrier and determination of photons ground state through its registration and the amplitude value of its carrier frequency as reference channel. So, it is necessary to solve problems of signal-to-carrier ratio of single photon detector (SPD) and aspects of photon number splitting (PNS) attack, nonlinear phase modulation (NPM) between carrier and sidebands in fiber, and finally, spectral selection of carrier in receiver. The technologies, based on the modulation conversion of an optical carrier, are widely used in microwave photonics. Due to the natural symmetry of modulated signals and the highest achievable ratio of the modulation conversions, amplitude-phase modulation with complete or partial suppression of the optical carrier has found a particularly wide application in MPS. The characteristics of advanced MPS for QKD with frequency coding and carrier suppression based on tandem amplitude modulation and phase commutation are presented. New systems can have classical symmetric or non-classical asymmetric structure for QKD based only on spectral selection of carrier and subcarriers without re-modulation.

**Keywords:** quantum key distribution, frequency encoding and decoding, photon-modulated components, amplitude, phase and meshed amplitude/phase modulation, tandem amplitude modulation and phase modulation or commutation, re-modulation, passive spectral selection without re-modulation, microwave photonics decisions

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