A Compact Gray-Code Quantum Read-only Memory for the NISQ Era

Hao Yu Lu1, Yu-Ting Kao2, Yeong-Jar Chang2, Chao-Hung Wang1, Darsen Lu1
1National Cheng Kung University, 2Industrial Technology Research Institute


Abstract

We propose GQROM, a programmable quantum read-only memory based on Gray code, designed to efficiently load classical data into quantum circuits as initial states. We demonstrate that by utilizing Gray code, GQROM minimizes transition complexity and reduces the required gate count to about one-third of conventional implementations. The GQROM design was implemented and validated on the Qiskit platform over a wide range of qubit count, making it potentially a scalable and hardware-friendly solution for state preparation in quantum circuits.