> The Gemini embedding model, gemini-embedding-001, is trained using the Matryoshka Representation Learning (MRL) technique which teaches a model to learn high-dimensional embeddings that have initial segments (or prefixes) which are also useful, simpler versions of the same data. Use the output_dimensionality parameter to control the size of the output embedding vector. Selecting a smaller output dimensionality can save storage space and increase computational efficiency for downstream applications, while sacrificing little in terms of quality. By default, it outputs a 3072-dimensional embedding, but you can truncate it to a smaller size without losing quality to save storage space. We recommend using 768, 1536, or 3072 output dimensions. [0]
looks like even the 256-dim embeddings perform really well.
[0]: https://ai.google.dev/gemini-api/docs/embeddings#quality-for...