Quantum Circuit Design for Solving Linear Systems of Equations

Abstract

Recently, it is shown that quantum computers can be used for obtaining certain information about the solution of a linear system Ax=b exponentially faster than what is possible with classical computation. Here we first review some key aspects of the algorithm from the standpoint of finding its efficient quantum circuit implementation using only elementary quantum operations, which is important for determining the potential usefulness of the algorithm in practical settings. Then we present a small-scale quantum circuit that solves a 2x2 linear system. The quantum circuit uses only 4 qubits, implying a tempting possibility for experimental realization. Furthermore, the circuit is numerically simulated and its performance under different circuit parameter settings is demonstrated.

7 pages, 3 figures. The errors are corrected. For the general case, discussions are added to account for recent results. The 4x4 example is replaced by a 2x2 one due to recent experimental efforts. The 2x2 example was devised at the time of writing v1 but not included in v1 for brevity

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• Quantum algorithm for solving linear systems of equations
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• Synthesis of Quantum Logic Circuits
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