QUAIL: Quantization Aware Unlearning for Mitigating Misinformation in LLMs

Fuente: arXiv
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Main Authors: Mishra, Himanshu, Mehreen, Kanwal
Format: Preprint
Published: 2026
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author Mishra, Himanshu
Mehreen, Kanwal
author_facet Mishra, Himanshu
Mehreen, Kanwal
contents Machine unlearning aims to remove specific knowledge (e.g., copyrighted or private data) from a trained model without full retraining. In practice, models are often quantized (e.g., 4-bit) for deployment, but we find that quantization can catastrophically restore forgotten information [1]. In this paper, we (1) analyze why low-bit quantization undermines unlearning, and (2) propose a quantization-aware unlearning method to mitigate this. We first compute weight-change statistics and bucket overlaps in quantization to show that typical unlearning updates are too small to cross quantization thresholds. Building on this insight, we introduce a logits space hinge loss: for each forget example, we force the output logits of the unlearned model to differ from the original model by at least a margin (half the quantization step). This ensures forgotten examples remain distinguishable even after quantization. We evaluate on language and classification tasks (including a Twitter misinformation dataset) and show our method preserves forgetting under 4-bit quantization, whereas existing methods almost entirely recover the forgotten knowledge.
format Preprint
id arxiv_https___arxiv_org_abs_2601_15538
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle QUAIL: Quantization Aware Unlearning for Mitigating Misinformation in LLMs
Mishra, Himanshu
Mehreen, Kanwal
Machine Learning
Artificial Intelligence
Machine unlearning aims to remove specific knowledge (e.g., copyrighted or private data) from a trained model without full retraining. In practice, models are often quantized (e.g., 4-bit) for deployment, but we find that quantization can catastrophically restore forgotten information [1]. In this paper, we (1) analyze why low-bit quantization undermines unlearning, and (2) propose a quantization-aware unlearning method to mitigate this. We first compute weight-change statistics and bucket overlaps in quantization to show that typical unlearning updates are too small to cross quantization thresholds. Building on this insight, we introduce a logits space hinge loss: for each forget example, we force the output logits of the unlearned model to differ from the original model by at least a margin (half the quantization step). This ensures forgotten examples remain distinguishable even after quantization. We evaluate on language and classification tasks (including a Twitter misinformation dataset) and show our method preserves forgetting under 4-bit quantization, whereas existing methods almost entirely recover the forgotten knowledge.
title QUAIL: Quantization Aware Unlearning for Mitigating Misinformation in LLMs
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2601.15538