Variational Quantum Circuit (VQC)

The multi-chip ensemble VQC framework addresses key QML challenges on Noisy Intermediate-Scale Quantum (NISQ) devices

It partitions high-dimensional computations across multiple smaller quantum chips, each running a subcircuit, with classical aggregation of outputs

Each chip processes a subvector of the input data using its own quantum circuit and data encoding unitary

Classical aggregation combines the outputs from all chips using a function (e.g., weighted sum or shallow neural network) for final predictions

Training is hybrid quantum-classical, with parameters for all subcircuits optimized collectively via backpropagation and parameter-shift rules

Scalability is achieved horizontally by adding more chips, avoiding the need for larger single chips or deep circuits

The architecture mitigates the barren plateau problem by restricting entanglement within chips, increasing gradient variance and improving trainability

The controlled entanglement structure acts as implicit regularization, reducing overfitting and improving generalization

Noise resilience is enhanced by limiting circuit depth per chip and averaging uncorrelated noise across chips, reducing both error variance and bias

The framework is compatible with current and future modular quantum hardware, addressing limitations like sparse connectivity and limited qubit counts