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Exponential concentration and symmetries in Quantum Reservoir Computing

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arxiv 2505.10062 v2 pith:VBGEQAWT submitted 2025-05-15 quant-ph

Exponential concentration and symmetries in Quantum Reservoir Computing

classification quant-ph
keywords quantumconcentrationexponentiallearningmachinebeyondcomputingperformance
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Quantum reservoir computing (QRC) is an emerging framework for near-term quantum machine learning that offers in-memory processing, platform versatility across analogue and digital systems, and avoids typical trainability challenges such as barren plateaus and local minima. The exponential number of independent features of quantum reservoirs opens the way to a potential performance improvement compared to classical settings. However, this exponential scaling can be hindered by exponential concentration, where finite-ensemble noise in quantum measurements requires exponentially many samples to extract meaningful outputs, a common issue in quantum machine learning. In this work, we go beyond static quantum machine learning tasks and address concentration in QRC for time-series processing using quantum-scrambling reservoirs. Beyond discussing how concentration effects can constrain QRC performance, we demonstrate that leveraging Hamiltonian symmetries significantly suppresses concentration, enabling robust and scalable QRC implementations. We illustrate our approach with concrete examples, including an established QRC design.

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Cited by 8 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Fisher-Orthogonal Memory in Quantum Reservoir Computing

    quant-ph 2026-07 conditional novelty 7.0

    Clifford-routed quantum reservoirs that store each past input along a distinct Pauli direction have diagonal Fisher memory matrices and outperform optimized random Ising reservoirs in simulated finite-shot delay tasks.

  2. Efficient classical training of model-free quantum photonic reservoir

    quant-ph 2026-04 unverdicted novelty 7.0

    Classical light training of photonic quantum reservoirs enables accurate model-free estimation of single-qubit observables and two-qubit entanglement witnesses on unseen quantum states.

  3. Diagnosing quantum reservoirs at scale based on expressivity and coverage

    quant-ph 2026-07 accept novelty 6.0

    Scalable ORS expressivity (top-K output probabilities vs Haar) plus effective feature rank jointly diagnose quantum-reservoir quality independent of Hilbert dimension and under hardware noise.

  4. Exploiting Symmetry in Quantum Reservoir Computing

    quant-ph 2026-07 accept novelty 6.0

    A quantum reservoir model that shares one encoding, circuit, measurement orbit, and readout across sensors is provably shift-equivariant and performs better than mismatched alternatives.

  5. Exploiting Symmetry in Quantum Reservoir Computing

    quant-ph 2026-07 unverdicted novelty 6.0

    Observable-orbit completion enforces symmetry across all interfaces in quantum reservoir computing for cyclic tasks by completing measurement channels to match input rotations.

  6. Measurement-enabled online quantum processing with amplitude encoding

    quant-ph 2026-06 unverdicted novelty 6.0

    A new protocol for online amplitude-encoded quantum reservoir computing is proposed that uses mid-circuit measurement and reset to implement partial-trace dynamics and indirect measurements for observables.

  7. Optimal quantum reservoir learning in proximity to universality

    quant-ph 2025-10 unverdicted novelty 5.0

    A tunable mixing parameter p in random quantum circuits controls the transition from classically simulable to expressive quantum reservoir dynamics via entanglement and nonstabilizer content.

  8. Quantum Reservoir Computing: Recent Advances and Future Directions

    quant-ph 2026-07 accept novelty 4.0

    A comprehensive survey of quantum reservoir computing that proposes a common system model, a memory-architecture taxonomy, and resource-accounting standards, concluding that no broad quantum advantage is currently dem...