# Performance Analysis of Quantum Key Distribution Technology for Power Business
## 2 Review of QKD Technology  
The development of QKD technology is based on communication theory and quantum mechanics. Through the generation, modulation and detection of quantum signals, information transmission is realized. According to the principle of indivisibility, uncertainty and no-cloning of single photons, any third-party behavior will affect the state of photon. Based on QKD protocol, the two parties negotiate and generate an absolutely secure quantum key based on the photon physical state as the information carrier. There are several types of QKD protocol, such as weak coherent pulses, true single photon signals, entangled photon signals and continuous variable signals.  
The BB84 protocol proposed by [PERSON] and [PERSON] in 1984 is the earliest quantum confidential communication protocol [25]. With the continuous research, a variety of QKD protocols based on the BB84 protocol have been proposed. The B92 protocol simplifies the BB84 protocol but reduces communication efficiency and practicability [26]. The six-state protocol is extended on the basis of the BB84 protocol, which raises the upper limit of the quantum error rate [27]. Limited to the existing single photon source technology, it is not possible to obtain ideal single photon. The decoy protocol was proposed to improve non-ideal single photon source BB84 protocol, which solves the problem of \"photon number separation attack\" [28]. At present, single photon QKD system mainly include polarization encoding and phase encoding. Taking polarization encoding as an example, the horizontal polarization state and vertical polarization state, \(\pm 45^{\circ}\) polarization state of the photon are used for encoding. Assuming that the state of photon polarization is horizontal or \(-45^{\circ}\) is defined as \"0\", then the description of vertical or \(45^{\circ}\) is \"1\". And there are corresponding measurement bases that are conjugate to each other. The sender sends the polarization state to the receiver. The receiver randomly selects one of the two conjugate groups and uses a photon polarization detector to measure the quantum polarization state. If the measurement base is the same as the transmission base, the accuracy of the polarization direction can be guaranteed. If the measurement base is not the same as the sending base, there is only a 50% probability that the correct polarization direction can be determined, and complete information cannot be accurately measured.  
Figure 1 and Table 1 describe the working principle of the quantum key distribution and the formation process of the quantum key, respectively. The transmitter of QKD system includes components, such as quantum signal source, modulator and random number generator and other components. First, a random number is generated by random number generator and then single-photon transmissions with different polarization states are prepared. After the receiver receives the single photon signal, it randomly selects the basis vector for measurement, and feeds back the measured basis vector to the sender. Finally, the sender tells the receiver the location of the common basis vector, and both parties retain the measurement result of the same basis vector as the quantum key. Meanwhile, the system selects a small number of quantum keys to calculate the bit error rate to determine whether there is third party behavior. In practical applications, the classic common signal in Figure 1 can use  
the same one. In this paper, we conduct research on the application of QKD technology based on polarization encoding in power industry.