[Resource Topic] 2025/626: Tree-based Quantum Carry-Save Adder

Welcome to the resource topic for 2025/626

Title:
Tree-based Quantum Carry-Save Adder

Authors: Hyunjun Kim, Sejin Lim, Kyungbae Jang, Siyi Wang, Anubhab Baksi, Anupam Chattopadhyay, Hwajeong Seo

Abstract:

Quantum computing is regarded as one of the most significant upcoming advancements in computer science.
Although fully operational quantum computers have yet to be realized, they are expected to solve specific problems that are difficult to solve using classical computers.
Given the limitations of quantum computing resources, it is crucial to design compact quantum circuits for core operations, such as quantum arithmetic.

In this paper, we focus on optimizing the circuit depth of quantum multi-operand addition, which is a fundamental component in quantum implementations (as an example, SHA-2).
Building on the foundational quantum carry-save approach by Phil Gossett, we introduce a tree-based quantum carry-save adder.
Our design integrates the Wallace and Dadda trees to optimize carry handling during multi-operand additions.
To further reduce circuit depth, we utilize additional ancilla qubits for parallel operations and introduce an efficient technique for reusing these ancilla qubits.

Our tree-based carry-save adder achieves the lowest circuit depth (T-depth) and provides an improvement of over 82% (up to 99%) in the qubit count–circuit depth product for multi-operand addition.
Furthermore, we apply our method to multiplication, achieving the lowest circuit depth and an improvement of up to 87% in the qubit count–circuit depth product.

ePrint: https://eprint.iacr.org/2025/626

See all topics related to this paper.

Feel free to post resources that are related to this paper below.

Example resources include: implementations, explanation materials, talks, slides, links to previous discussions on other websites.

For more information, see the rules for Resource Topics .