Research On Quantum Circuits Synthesis And Fault-tolerant Methods

Theoretically reversible logic dissipates zero power since the input vector of reversible circuitcan be uniquely recovered from the output vector. Reversible computation has applications in digitalsignal processing, low power design and quantum compution. The quantum circuit is a typicalreversible circuit, Therefore, research the synthesis and fault-tolerant method fou quantum circuits hasthe important theory signicicance and the project practical value. Quantum circuits can be constructedby cascading and combining the basic quantum gates. In order to automatically design the optimalquantum, the new synthesis method must be more efficeiency and versatility. And in order to increasethe reliability for quantum circuits, the new fault-tolerant method should be studied. The mainresearch works of this paper are listed as follows.(1) Research on the evolutionary design theory for the synthesis of quantum circuits. Throughadd the new performance indicators such as time delay and logic complexity and so on; make themathmatic model have more objective function, so the obtained circuits are better than before. Wetransform synthesis of quantum circuits to gain the objective function of mathematical model, so wecan get the optimal circuits automatically by the intelligence algorithm. Besides, a newmulti-objective evolutionary design for quantum based on two-dimensional variable-lengthchromosome was proposed in this paper. Aiming to sybthesis the large scale quantum circuits, firstlythe circuit was divided to several sub-circuits, and then used the evolutionary method to design thecircuit. The new encoding mode and the new evolutionary mentod can reduce the difficulty ofsynthesis for the large sacle quantum circuits. The experimental results show that the proposedsynthesis algorithm can achieve better comprehensive performances.（2）Research on the fault-tolerant method for quantum circuit. Based on the input and outputparity-preserving characteristic of quantum logic gate, a specific online failure detection method forthe quantum circuits which completely composed of parity-preserving gate is proposed. Throughdetecting the parity-preserving characteristic of the gate to be tested using newly constructed signaldectecting circuit and failure detecting gate, the failure can be located. In the meantime, the signaldetecting circuit can be tested increasing the reliability of the detecting system and providing amethod for the fault-tolerant design of quantum circuit based on hardware redundancy. Then, asecondary parity-encapsulation method is proposed for the general quantum logic gates withoutparity-preserving characteristic. By adding input and ouput to no parity-preserving gate, the previous gate gains the same characteristic as the parity-preserving gate. In addition, the circuit is divided intoseveral sub-circuits. Through self-repairing design for the several sub-circuits, hardware cost and thenumber of garbage outputs are reduced which greatly increases the fault-tolerance capability and thereliability of the quantum circuits.