Multivalued quantum encoding maps a classical alphabet of $M>2$ symbols onto multiple prescribed states. Here, we experimentally demonstrate multivalued quantum encoding in an effective two-level subspace of the electron spin of a nitrogen-vacancy center in diamond at room temperature. Classical symbols are mapped onto either the qubit population (polar angle $\theta$) or the coherence (azimuthal angle $\varphi$) via microwave pulses with controlled durations or phases. By coherently preparing four distinct states within the electron-spin qubit, we demonstrate image reconstruction symbol by symbol. No decoding errors are observed for the tested finite datasets under the reported repetition settings. To enhance robustness to channel noise, we further integrate an error-adaptive joint source-channel coding (EAJSCC) neural codec, which achieves a 2% compression ratio with a structural similarity index (SSIM) of 0.78, compared with SSIM approximately equal to $0.24$ for a conventional baseline. These results establish a viable route toward higher information density in room-temperature solid-state spin platforms.

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• Coherent control
• Quantum algorithms
• Quantum information processing
• Nitrogen vacancy centers in diamond