Application Of Quantum Process Tomography And Quantum Detector Tomography

With the great development of quantum information technology, human beings have learnt the world much more deeply from the new aspect. It has been over a decade since Einstein proposed the principle of stimulated emission in 1916. During this time, quantum optics has got considerable development, especially in recent years, with our deeper understanding of what light really is. Meanwhile, quantum information technology based on the research of photons is becoming researched and applied. As is known, if a single quantum system is undetectable, we can barely obtain its complete information. However, a laser source is considered as one of the most basic quantum state-a coherent state, which means the quantum states of the laser are totally same regardless of time varying. By measurements on different copies, we can then estimate the quantum state of an unknown system, which is named as the quantum tomography technology. Quantum state tomography (QST), quantum process tomography (QPT) and quantum detector tomography (QDT) are three basic components of the quantum tomography, which have intimate connections. Since a complete mathematical model can be formed to formulate the information we get, this technology can be promoted into application. This paper starts from quantum state tomography to the application of quantum process tomography and quantum detector tomography. As is known to us, there is an attractive prospect of the surface plasma due to its novel propagation property in nano-photonics, catching a lot of eyes recent years. Nevertheless, people’s understanding about the process of the surface plasma is confined to the classical optics. Apparently, the quantum process tomography is a powerful tool to explore the deeper nature of the surface plasma from the aspect of quantum level. In my work, a measuring experiment platform was established with a few photons and we got a completely characterization for the surface plasma in quantum perspective for the first time. Over and done with the research, it seems that QPT can declare more information of the involving process of the system and also open a way to apply this technology to other relative region. Quantum detector is the bridge which is linking the quantum and classic, so it is important to demarcate its quantum characteristic, and the additional evidences of the application shown by the complete representation of the quantum detector’s characters. According to the QDT theory, we improved the experimental scheme of the QDT which using two-mode squeezing vacuum state. In order to enhance the fidelity of the quantum detector, we put a high spilt ratio beam-splitter into one arm of the experiment design. This modification can bring in a more accuracy measurements without increasing the number of measurements, in other words, it can reduce the number of measurements to get the same accuracy compared with the original experiment. The results of measurements are always accompanied by errors, but the errors can be condensed by multiple metering, however, it won’t be decrease to zero because of the finite measurements. So using finite measurements to increase the accuracy is a chief target. In this paper, a method is introduced to improve the sensitivity and resolution of the phase estimation using the Mach-Zehnder interferometer by the photon annihilation or photon addition. The resolution of the interferometer achieves the Heisenberg limit after calculation, moreover, the effect of the photon addition to the two-mode squeezed state is better than the annihilation.