FPGA-based Digital Quantum Coprocessor

: pp. 67-83
Lviv Polytechnic National University, Department of Electronic Computing Machines
Lviv Polytechnic National University, Computer Engineering Department

Classical quantum computer is an analog probabilistic computer. The digital quantum computer that can be implemented in FPGA has been described in the article. Digital quantum coprocessor is designed to implement algorithms for execution on the analog quantum computers. A digital quantum coprocessor operates under the control of a classical computer and together they are digital quantum computer. The digital quantum coprocessor is a set of digital units called digital qubits that have multi-bit data input and single-bit data output each. The digital qubit is a wave function calculator. Thereis a pseudo random number generator (PRNG) in the described digital qubit to generate the probabilistic output bit. Singlebit qubit output qb has been formed by the probable reduction of its multi-bit result x to single-bit (0 or 1) according to result value x and pseudo random code k (x is an angle which determines the position of normalized vector with length 1 in polar grid, it is a result of multi-bit input data calculation). The decision about output state has been made after the functional conversion of the qubit multi-bit result x to result probability p = sin2x and subsequent comparison p with the pseudo random code k. Qb=1 when k < p. In the article, the inverse variant of decision option with p = arcsin (sqrt (k)) and Qb = 1 when x > p has been described. This variant allows to use one PRNG for all digital qubits. Possible schemes for digital qubit and digital quantum coprocessors based on them have been discussed in the paper. The presentation of data in digital qubits and the basic operations they perform have been also considered. The results of the simulation of a four-qubit digital quantum coprocessor and the results of the qubitimplementation in FPGA have been presented.

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