Quantized Markov Chain Couplings that Prepare Qsamples

Quantum 9, 1951 (2025).

https://doi.org/10.22331/q-2025-12-18-1951

We present a novel approach to quantizing Markov chains. The approach is based on the Markov chain coupling method, which is frequently used to prove fast mixing. Given a particular coupling, e.g., a grand coupling, we construct a completely positive and trace preserving map. This quantum map has a unique fixed point, which corresponds to the quantum sample (qsample) of the classical Markov chain’s stationary distribution. We show that the convergence time of the quantum map is directly related to the coupling time of the Markov chain coupling.