Nature Scientific Reports
Multi-Qubit Correction for Quantum Annealers
July 8, 2021
We present multi-qubit correction (MQC) as a novel postprocessing method for quantum annealers that views the evolution in an open-system as a Gibbs sampler and reduces a set of excited states to a new synthetic state with lower energy value. After sampling from the ground state of a given (Ising) Hamiltonian, MQC compares pairs of excited states to recognize virtual tunnels — i.e., a group of qubits that changing their states simultaneously can result in a new state with lower energy value — and successively converges to the ground state. Experimental results using D-Wave 2000Q quantum annealers demonstrate that MQC finds samples with notably lower energy values and improves the reproducibility of results when compared to recent hardware/software advances in the realm of quantum annealing, such as spin-reversal transforms, classical post-processing techniques, and increased inter-sample delay between successive measurements.
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