Quantum random access memory via quantum walk

TL;DR

This paper introduces a quantum random access memory (qRAM) design based on quantum walks, which reduces coherence maintenance costs, is fully parallelized, and simplifies the structure compared to previous models.

Contribution

It presents a novel qRAM scheme utilizing quantum walks and a bucket brigade approach, eliminating the need for quantum devices at tree nodes and enabling efficient, parallel data access.

Findings

Requires only O(n) steps to access 2^n data entries

Reduces coherence maintenance costs by avoiding quantum devices at nodes

Enables fully parallelized quantum data retrieval

Abstract

A novel concept of quantum random access memory (qRAM) employing a quantum walk is provided. Our qRAM relies on a bucket brigade scheme to access the memory cells. Introducing a bucket with chirality left and right as a quantum walker, and considering its quantum motion on a full binary tree, we can efficiently deliver the bucket to the designated memory cells, and fill the bucket with the desired information in the form of quantum superposition states. Our procedure has several advantages. First, we do not need to place any quantum devices at the nodes of the binary tree, and hence in our qRAM architecture, the cost to maintain the coherence can be significantly reduced. Second, our scheme is fully parallelized. Consequently, only O(n) steps are required to access and retrieve O(2n) data in the form of quantum superposition states. Finally, the simplicity of our procedure may allow the design of qRAM with simpler structures.