Database Processing In Quantum Computers

Quantum database processing is the basic process of information transmissionand information processing in quantum computers. It is an important topic in researchareas and has attracted attention of scientists. In this thesis, we focus on four areasin quantum database processing, i.e., analytic construction of quantum gates, quan-tum database processing, database processing based on duality properties and quantumcomputation with nonlinear optics.In the field of quantum circuit, we propose two theoretical protocols. Firstly,we present two analytic expressions that most generally simulate n-qubit controlled-Ugates using universal one-qubit gates and CNOT gates with exponential and polynomialcomplexity respectively. Based on analytic results of quantum gates, we present afull Bell, GHZ and W basis-states analyzer. It provides a new method and view forexperimental design of state initialization and quantum measurement.In the field of quantum database processing algorithm, we propose five new al-gorithms, i.e., quantum deletion algorithm which deletes a marked basis-state from aneven superposition of all basis-states with a single query, generalized quantum dele-tion algorithm which deletes M marked basis-states from arbitrary initial superposedstate, approximate quantum deletion algorithm which uses a fixed phase rotationπ/3to approximately delete a marked basis-state from a large database, quantum insertionalgorithm which inserts a marked basis-state into a superposed state with a single queryand generalized quantum search algorithm which searches M marked basis-states fromarbitrary initial distribution with certainty. The former four algorithms can achieve anexponential speedup compared to classical computing, the latter one algorithm is thegeneralization of the Long quantum search algorithm.In the field of database processing based on duality properties, to realize dualitycapability in quantum computers, we present duality mode and recycling mode of quan-tum computers to simulate a 2-slit symmetric duality computer. We present general- ized duality mode and generalized duality gates to simulate arbitrary duality computerin quantum computers. In addition, a fixed-point search algorithm and two fixed-pointdeletion algorithms in quantum computers using duality mode are presented.In the field of quantum computation with nonlinear optics, we propose a schemeof nonlinear optics quantum computation implemented by Mach-Zehnder interferom-eter, magnetic-induced Faraday rotation device, positive and negative uniaxial crystalwith second susceptibility and polarization-plastic device. Under ideal conditions, thesuccess probability of our scheme is deterministic or near-deterministic.