Experimental Research Of An Interaction-free-measurement-based Quantum Communication Protocol

Secure communications has a very long history,which involves the telegraph,the military,mobile communications,E-mail,and so on.it is also a integrated disciplines which involves information theory,physics,computer,mathematics,communications and other fields.Secret key in the process of traditional encryption keys should be made up of random binary string for private or public key technology,the encoded ciphertext can transfer on public transport channel after the key established fully.The security of the ciphertext is difficult to guarantee In the actual communication,the recipient wouldn't even be aware of the situation that the key distribution has been bugged because of the interference of eavesdroppers through the channel.In the last few years,the combination system of cryptography and quantum mechanics using quantum state as the carrier of information,then transferring the key between the sender and recipient through the quantum channel.The Heisenberg's uncertainty principle guarantee the reliability of quantum cryptography,That is,the quantum states will be changed when it is measured and result in collapse of the wave function,the eavesdropper cannot complete copy the information in the transmission channel.In principle,we won the secret communication system that is unassailable and not wiretapped.This paper analyzes the interlink Mach-Zehnder interferometers?MZIs?and showing that the interaction-free measurement?IFM?can be carried out by the direct counterfactual communication.we perform a experiment of an IFM based quantum communication protocol with weak coherent light.mainly contains following four parts:The first chapter is introduction that describes secret communication process and basic knowledge,which including the classic secret communication,quantum secret communication and quantum key distribution,we also analyzed the physical mechanism of IFM and expounds the development and application.The second part gives the theoretical derivation of the quantum states in the MZIs,and designs a experimental scheme of multiple-series connection of MZIs,and find that the detection of the intensity ratio of the two final outputs tells of the operation of logic gate in the transmission channels by theoretical the calculation.In the third part,in order to obtain the security and stability of quantum direct communication in experimental measurement,we first analyzed the saturated absorption spectroscopy of cesium atom related to D₁ and D₂ line.We locking the output frequency of laser with 895nm wavelength through the polarization spectrum,we also simulate the quantum communication protocol based on IFM and obtained a high efficiency of the IFM.We further improve the research design on this basis,and showing the intensity ratio of the two outputs of the experimental system and the value of the reliability of the IFM,and made an analysis and comparison.In the fouth part,we present a proposal for the basic setup which is embedded in an unbalanced Mach-Zehnder interferometer based on“chained”Zeno effect.Then we take the image as the transmission light source with the frequency difference,and the light intensity distribution in cross section will be captured by CCD.For the case with objects in the path,CCD at the two outputs will capture the separate and different image respectively.this proposal contribute to improve the interaction-free efficiency in a very small number of interferometers under the practical measurement.The innovative works are:I.We research an experiment of the counterfactual communication based on the interaction-free measurement.and analyze the propagation process of the system by using the transfer-matrix method.We showed that the practical scheme of high-efficiency interaction-free measurement with low number of optical devices and instability factors is accessible.II.Perform the quantum counterfactual-like communication with a high efficiency of interaction-free using the weak coherent light.and further optimization of experimental system,which demonstrate the improvement of the reliability using dissipation compensation in interferometers.III.We present a novel approach to achieve the high efficiency interaction-free measurement by using an unbalanced MZI.With this setup based on Zeno effect in“chained”Mach-Zehnder interferometers,we take advantage of the image transmission,which showing in principal that the high efficiency could be carried out with a very small number of imperfect interferometers.