Quantizing open-vocabulary object detection (OVOD) models reduces their memory and computational costs, but extremely low-bit quantization severely degrades both cross-modal (region-text) and intra-modal (region-region) alignments. This multimodal degradation is a unique challenge that prior quantization methods for closed-vocabulary detectors fail to resolve. To overcome this, we propose Quantization-Aware Training with Multimodal Alignment (QATMA), the first multimodal-aware and architecture-agnostic QAT framework tailored for OVOD. QATMA integrates two key components: (i) Curriculum QAT, which partitions the detector by functional roles and progressively expands the quantization scope to suppress error accumulation and ensure stable optimization; and (ii) Text-anchored Pairwise Similarity Distillation, which transfers both region-text and region-region alignments from a full-precision teacher model via pairwise cosine similarities in the joint embedding space. Experimental results on LVIS and COCO zero-shot benchmarks demonstrate that QATMA significantly outperforms existing QAT baselines under extremely low-bit settings, achieving gains of up to 4.3 and 7.6 AP, respectively.
Figures & tables
Figure 1: Impact of 4-bit quantization on YOLO-World [ 7 ] ( Objects365v2 [ 44 ] ). (a) Confidence scores from the similarity between each region embedding and the “Train” text embedding ( Pˉ : mean over positive regions). (b) Pairwise cosine similarity matrix among positive region embeddings within the same category ( r : Pearson correlation with FP32). (c) Quantitative comparison of embedding distortion relative to FP32; closer to the origin indicates less distortion.
Figure 2: Overview of the proposed QATMA framework. ( Red ) blocks denote quantized and learnable modules, and ( blue ) blocks denote full-precision and frozen modules. (a) Stage 1: the backbone ( M1 ) is quantized with Lfeat supervision from the full-precision teacher, while the neck-head remains frozen for error isolation. (b) Stage 2: the neck-head ( M2 ) is additionally quantized, supervised by both Lfeat and LTPSD . (c) Feature distillation aligns the student’s multi-scale backbone features f1S(x) to those of the teacher f1T(x) . (d) TPSD groups region embeddings by text query tc and constructs a unified pairwise similarity matrix Sc to transfer region-text and region-region alignment.
Model
Bits
Size(MB)
BOPs(T)
Method
AP
AP r
AP c
AP f
YOLO-World-M
FP32
110.88
51.82
-
31.0
23.8
29.2
33.9
4-4-8
15.11
7.10
QAT
13.8
10.7
11.6
16.3
EMA+QC [ 16 ]
13.7
11.8
12.2
15.4
QFD [ 57 ]
13.0
7.1
11.0
15.8
Ours
16.3
11.4
14.5
18.8
YOLO-World-L
FP32
181.4
98.39
-
35.4
27.6
34.1
38.0
Table 1: LVIS minival zero-shot evaluation with 4-4-8 quantization (Ch-T-H granularity). Ch = per-channel, T = per-tensor, H = per-head. Evaluation follows the LVIS fixed AP protocol [ 10 ] .
Figure 4: Qualitative comparison on YOLO-World-L (4-4-8, Ch-T-H). ( Top ) Detection results. ( Bottom ) Region-region similarity heatmap of average pairwise cosine similarity among same-class anchors. QAT distorts both detection and similarity patterns of FP32, whereas QATMA restores them.
Appendix figures & tables6 assets
Supplementary material from the paper’s appendix.
Appendix
Model
Bits
BOPs(T)
Method
AP
AP 50
AP 75
AP s
AP m
AP l
YOLO-World-M
FP32
44.56
-
41.9
57.0
45.5
26.7
46.1
55.0
4-4-8
2.05
QAT
22.0
32.1
23.6
7.8
23.5
32.4
EMA+QC [ 16 ]
21.2
31.1
22.7
8.3
22.7
31.3
QFD [ 57 ]
21.6
31.4
23.3
7.9
23.7
31.8
Ours
26.1
38.1
28.1
11.0
28.1
37.9
YOLO-World-L
FP32
90.60
-
45.1
60.7
48.9
29.8
49.8
57.5
Appendix
Table 7: Full COCO val2017 zero-shot comparison, including the EMA+QC [ 16 ] and QFD [ 57 ] closed-vocabulary detection QAT baselines (4-4-8, Ch-T-H granularity).
Granularity
Bits
Method
LVIS
COCO
Ch-T-H
4-5-8
QAT
23.0
36.2
Ours
23.8
37.6
Ch-Ch-H
3-3-8
QAT
18.5
30.7
Ours
20.0
32.6
Appendix
Table 8: Effect of quantization granularity and bit-width on YOLO-World-L. Ch-Ch-H = per-channel activations. LVIS and COCO zero-shot AP is reported.
Stage 1 (backbone)
Stage 2 (neck-head)
AP
1/3
2/3
16.1
1/2
1/2
15.0
Appendix
Table 9: Effect of the curriculum data split between Stage 1 (backbone) and Stage 2 (neck-head) on YOLO-World-L (4-4-8, Ch-T-H). LVIS zero-shot AP is reported.
λ2
0
3
6
12
18
48
AP
30.4
30.8
31.2
31.2
31.0
30.9
Appendix
Table 10: TPSD loss weight λ2 sensitivity on YOLO-World-L (head-only W4A4). LVIS zero-shot AP is reported.
Method
GFLOPs/iter
GPU-hours
QAT
27.1k
95.2
Ours
35.1k
112.4
Appendix
Table 11: Training cost on YOLO-World-L. QATMA adds no inference cost, and its two-stage training overhead over plain QAT is modest.
Figure 5: Qualitative comparison of LVIS zero-shot detection on YOLO-World-L (4-4-8, Ch-T-H)