UNIVERSAL HYBRID QUANTUM PROCESSORS
Alexander Yu. Vlasov · 2003
A quantum processor (the programmable gate array) is a quantum network with a ˇxed structure. A space of states is represented as tensor product of data and program registers. Different unitary operations with the data register correspond to ®loaded ¯ programs without any changing or ®tuning¯ of network itself. Due to such property and undesirability of entanglement between program and data registers, universality of quantum processors is subject of rather strong restrictions. Universal ®stochastic¯ quantum gate arrays were developed by different authors. It was also proved, that ®deterministic¯ quantum processors with ˇnite-dimensional space of states may be universal only in approximate sense. In the present paper it is shown that, using hybrid system with continuous and discrete quantum variables, it is possible to suggest a design of strictly universal quantum processors. It is also shown that ®deterministic ¯ limit of speciˇc programmable ®stochastic ¯ U(1) gates (probability of success becomes unit for inˇnite program register), discussed by other authors, may be essentially the same kind of hybrid quantum systems used here.