Quantum Walk on Dimensionality Reduced Complete Bipartite Graphs with k Edges Removed

Abstract

Due to scalability issue in current quantum technologies, many quantum algorithms can only be implemented for small size problems. Scalability remains a bottleneck for current quantum technologies. For solving real-life size hard problems in the near-term, we explore classes of search graphs that can be efficiently reduced to a implementable scale for many quantum algorithms. The reduced Hamiltonian preserves the dynamics of the original Hamiltonian. One of the quantum algorithms we choose for the reduced Hamiltonian is continuous time quantum walk (CTQW). We further show how to determine the correct value of the coupling factor of the underlying CTQW. With wrong couple factor values, the optimality (quadratic speedup) from CTQW might be lost. In this work, we extend the class of reducible graphs to complete bipartite graphs with random $k$ edges removed. We further demonstrate through mathematical proof and simulation experiment using IBM Qiskit to show that the quadratic speed-up is preserved for the CTQW.