Resonating with RoPE: Spectral Quantization for High-Fidelity Key Cache Compression

Xuefei Wang, Haoyu Tang, Tianyuan Liang, Zhibin Wang, Yupeng Hu, Weili Guan


Abstract
The linear growth of KV cache bottlenecks long-context LLMs, yet RoPE-induced oscillations complicate Key cache quantization. To address this issue, we propose SpectrumQuant, a frequency-domain framework that utilizes the Discrete Cosine Transform (DCT) to convert these oscillations into sparse spectral representations. Specifically, our pipeline integrates dominant frequency extraction, hybrid bit-width allocation, and high-frequency pre-emphasis to maximize fidelity while minimizing memory footprint. To eliminate computational overhead, we develop fused Triton kernels featuring deferred inverse transformation and on-chip sparse accumulation. Extensive experiments on several benchmarks confirm SpectrumQuant achieves efficient compression with performance and latency comparable to FP16 baselines.
Anthology ID:
2026.acl-long.1732
Volume:
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
37328–37348
Language:
URL:
https://preview.aclanthology.org/ingest-acl/2026.acl-long.1732/
DOI:
Bibkey:
Cite (ACL):
Xuefei Wang, Haoyu Tang, Tianyuan Liang, Zhibin Wang, Yupeng Hu, and Weili Guan. 2026. Resonating with RoPE: Spectral Quantization for High-Fidelity Key Cache Compression. In Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 37328–37348, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Resonating with RoPE: Spectral Quantization for High-Fidelity Key Cache Compression (Wang et al., ACL 2026)
Copy Citation:
PDF:
https://preview.aclanthology.org/ingest-acl/2026.acl-long.1732.pdf
Checklist:
 2026.acl-long.1732.checklist.pdf