Microwave is widely used in present navigation system. It works well, yet it faces precision limit and other challenges. Quantum entanglement has been applied in various fields and resulted in quite remarkable improvement, especially in precision performance, as it can break quantum noise limit. Hence, we attempt to apply quantum entanglement to enhance merits of navigation system performed in microwave regime. This paper introduces principles of quantum microwave entanglement prepared by electro-opto-mechanical converters in detail, which is also adopted by quantum illumination. Meanwhile, a navigation scheme enhanced by quantum microwave entanglement is proposed. The working principles of the scheme, especially those of location, range finding and direction finding, are analyzed in detail. Besides, we compare navigation scheme of quantum microwave entanglement with present navigation scheme. It shows that navigation merits have been enhanced by quantum microwave entanglement, and it may be regarded as a candidate of new navigation method.
State of polarization(SOP) of single photon is the information carrier of polarization encoding BB84 protocol. SOP of quantum must be interrupted when quantum key distribution(QKD) propagates with classical signal in the same fiber. Coexistence schemes of quantum-classical signal based on two-channel and four-channel have been built respectively on Optisystem in this paper. The influence on SOP of quantum signal in BB84 protocol from different classical optical signal channel has been analyzed and compared by Stokes vector method and Poincare sphere method. SOP of 100 photons in QKD have been simulated. The results show that more channels will increase the bit error rate of QKD, and this paper has described the SOP changes well in coexistence scheme of quantum-classical signal based on wavelength division multiplexing.
In order to improve the detection efficiency in QKD system, this paper has put forward a new quantum key distribution scheme based on the single photon frequency up-conversion detection technology and decoy-state BB84 protocol. A long wavelength pump light is adopted in single photon detector (SPD) to avoid the noise caused by spontaneous parametric down conversion (SPDC), thus an overall 28% detection efficiency is achieved which is five times of 4.5% in conventional InGaAs-based detectors. Moreover, the propagating distances has reached 90km and 150km with weak coherent pulse (WCP) and decoy weak coherent pulse (DWCP) respectively, which is 1.3 times and 1.05 times of the conventional InGaAs-based detectors of 70km and 140km.
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