ACM Turing Celebration Conference - China (ACM TURC)
QuantaBit: Quantum-Assisted Mixed-Precision LLM Quantization and Inference
Yuchen Li, Gongwei Li, Zihang Fang, Juncheng Jia, Jian Tang, Zhiguo Huang, J. Z. Han, Ruochen Liu
Abstract
QuantaBit integrates a quantum-enhanced quantization solver with a mixed-precision inference engine. Starting from a pretrained FP16 Large Language Model (LLM), it analyzes layer-wise sensitivity, constructs a Hamiltonian that combines quantization-induced accuracy loss with compression loss, maps candidate bitwidths to compact binary variables, and finally solves the resulting QUBO on a Coherent Ising Machine (CIM). The decoded mixed-precision bitwidth allocation is then used to perform mixed quantization. QuantaBit invokes the inference engine for bitwidth-aware packing, heterogeneous kernel dispatch, and PagedAttention-based KV-cache management. Experiments on four LLMs show that QuantaBit decreases perplexity over uniform W4 and Cplex under the same average-bitwidth target, while deployed models reduce weight memory by over 3.4x, improve throughput by 15%, and extend context length by 53%.