The Grover search as a naturally occurring phenomenon

Abstract

We provide first evidence that under certain conditions, 1/2-spin fermions may naturally behave like a Grover search, looking for topological defects in a material. The theoretical framework is that of discrete-time quantum walks (QW), i.e. local unitary matrices that drive the evolution of a single particle on the lattice. Some QW are well-known to recover the $(2+1)$--dimensional Dirac equation in continuum limit, i.e. the free propagation of the 1/2-spin fermion. We study two such Dirac QW, one on the square grid and the other on a triangular grid reminiscent of graphene-like materials. The numerical simulations show that the walker localises around the defects in $O(\sqrt{N})$ steps with probability $O(1/\log N)$, in line with previous QW search on the grid. The main advantage brought by those of this paper is that they could be implemented as `naturally occurring' freely propagating particles over a surface featuring topological---without the need for a specific oracle step. From a quantum computing perspective, however, this hints at novel applications of QW search : instead of using them to look for `good' solutions within the configuration space of a problem, we could use them to look for topological properties of the entire configuration space.

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Cited by in corpus (9)

• Number Partitioning with Grover's Algorithm in Central Spin Systems
• Quantum-classical distance as a tool to design optimal chiral quantum walk
• Quantum Bandits
• Quantum Amplitude Amplification Operators
• Efficient implementation of discrete-time quantum walks on quantum computers
• Quantum spatial search with electric potential : long-time dynamics and robustness to noise
• Searching via nonlinear quantum walk on the 2D-grid
• Quantum Walks, Feynman Propagators and Graph Topology on an IBM Quantum Computer
• Quantum Perceptron Revisited: Computational-Statistical Tradeoffs