Fault tolerant resource estimation of quantum random-access memories

TL;DR

This paper analyzes the resource costs of fault-tolerant quantum random-access memory (qRAM), proposing circuit families, exploring tradeoffs, and estimating requirements within surface code error correction.

Contribution

It introduces generic circuit families for fault-tolerant qRAM, discusses qubit-time tradeoffs, and estimates resource costs in surface code implementations.

Findings

Circuit families for fault-tolerant qRAM are constructed.

Tradeoffs between qubit count and operation time are identified.

Resource estimates for surface code implementations are provided.

Abstract

Quantum random-access look-up of a string of classical bits is a necessary ingredient in several important quantum algorithms. In some cases, the cost of such quantum random-access memory (qRAM) is the limiting factor in the implementation of the algorithm. In this paper we study the cost of fault-tolerantly implementing a qRAM. We construct and analyze generic families of circuits that function as a qRAM, discuss opportunities for qubit-time tradeoffs, and estimate their resource costs when embedded in a surface code.