Theoretic Research On Quantum Process Tomography

When characterizing a quantum system's dynamic characteristics, it is necessary to determine its mathematic description. Quantum operation is a good description of an open quantum system. And quantum process tomography is a procedure by which an unknown quantum operation can be fully experimentally characterized. It plays an important part in many scopes, such as quantum communication and quantum calculation. In this paper, OSR (operator-sum representation) is used as the description of quantum operation, and a research is done on quantum process tomography. To be more specific,1,Summarize fundaments and normal steps of quantum process tomography, and make a qualitative contrast between quantum process tomography and system identification. Quantum process tomography is a procedure by which an unknown quantum operation can be fully experimentally characterized. And system identification can estimate an unknown system's mathematical description. A contrast between two methods of system estimation, gives out that the differences are based on which quantum measurement can only get partial information of the quantum state.2,Summarize how to design quantum state tomography, and analyze how to optimize the times of different measurements. Quantum measurement can't get all information of the quantum state, so it needs quantum state tomography to reconstruct the output quantum state. And in quantum state tomography, different measurements on the same quantum state have interactions. So it is necessary to do optimality analysis.3,Analyze the evolvement of quantum system when doing continuous measurement on it, and give a general mathematical description of the evolvement. At the present time, when using quantum process tomography, suppose all operators of OSR are constants. But they are timevarying in most of quantum systems. For estimating the timevaring OSR, it is necessary to carry out a sequence of measurement.