# Quantum Multi-User Broadcast Protocol for the \"Platform as a Service\" Model
## 5 Conclusions  
We describe a multi-user broadcast protocol in network for the one-to-many multicast communication network including the master and \(N\) slave mode using a sequence of single photons. This protocol might be useful in practice because it guarantees multicast information robustness. In the one-to-many multicast communication mode, \(S_{0}\) creates \((4n+\delta)\) random bits and multicasts information to \(S_{i}(i=1,2,\cdots,N)\). \(S_{0}\) and \(S_{i}\) publicly announce the selection of the random measurement basis. There are at least \(2n\) bits left, and if not, the protocol will be aborted. Meanwhile, the Calderbank-Shor-Steane (\(CSS\)) coding theory can be employed for correcting the errors introduced by the noisy communication channel. Therefore, the \(N+1\) nodes compute the related information, and finally obtains the correct key. The commercial success of quantum key distribution for the generation of a private shared secret key motivates this investigation. The protocol is also proved to be unconditionally secure in theory, which indicates its feasibility in theoretical application. For future study, it may be significant to investigate the performance of our protocol for encoding secret classical messages.  
In our proposed protocol, the photon is the carrier of information. Quantum information is encoded in the flying photon bit, and the transmit power is related to the performance of the transmitter module. In practical quantum communication, the transmission distance is limited due to the imperfection of the transmitter module and the detection module, which is a general problem in all practical quantum communication systems.  
This protocol mainly establishes the quantum multi-user communication model without considering channel noise. In the practical noisy channel, we can use the quantum error-correction code to correct the error generated in the transmission process. Commonly used quantum error-correction codes are Quantum Stabilizer Code (QSC) and Quantum Low-Density Party-Check Code (QLDPC) [28].  
One thing to point out is that we concentrate only on closed systems where the decoherence and dissipations are neglected. It is well-known that in open quantum systems the Hamilton operator is non-Hermitian [29; 30]. The dynamical behavior of open quantum systems plays a key role in many applications of quantum mechanics, such as the environment-induced decay of quantum coherence, relaxation in many-body systems, and applications in condensed matter theory, quantum transport, quantum chemistry, and quantum information. If the decoherence and dissipation of the open systems are considered, the protocol based on quantum error correction coding needs to be studied in the future in more detail.  
Conceptualization, H.M.; methodology, H.M. and P.S.; validation, N.L. and S.W.; investigation, S.W. and Z.L.; writing--original draft preparation, P.S. and H.M.; writing--review and editing, P.S. and N.L.; and visualization, M.R.  
This work was supported by the Project of Shandong Province Higher Educational Science and Technology Program (No. J18 KZ012), the National Natural Science Foundation of China (Nos. 61772295 and 11975132), and the Natural Science Foundation of Shandong Province (No. ZR2016 FB09).  
The authors declare no conflict of interest.