Two-Spin Exchange-Only Chains Reach 90.9% MNIST Accuracy Without Magnetic Gradients
The work shows that symmetry-protected constraints of two-spin units can be lifted by inter-pair exchange without added hardware complexity. This reduces the physical overhead of exchange-only QML while preserving competitive accuracy on a standard benchmark. Further experiments on actual devices will be required to confirm whether the simulated expressibility survives decoherence and fabrication variation.
The architecture replaces universal gate synthesis with time-domain evolution of a spin chain whose inter-pair couplings mix singlet-triplet subspaces that isolated pairs cannot reach. Numerical experiments on 10,000 MNIST images show the learned pulse sequence outperforms both a classical linear readout on identical PCA features (83.2%) and an untrained reservoir version of the same dynamics (53.0%). Robustness holds under 10% pulse-area noise and 10^3-shot readout, indicating the protocol tolerates realistic semiconductor imperfections.
Minato et al.: Within 18 months a GaAs or Si/SiGe device will demonstrate >85% MNIST accuracy under the reported pulse protocol with measured T2 > 1 us.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2608.29017)
- [2]Supporting Source(https://arxiv.org/abs/2305.01765)