Researchers Cut Complexity of Quantum State Estimation

A new method accurately describes quantum states using substantially fewer computational resources than previously possible. The framework represents the ‘density matrix’, which defines a quantum state, as a compressed form utilising block tensor train factorization; this compresses optimisation variables from an exponential scale to one that grows linearly with qubit count. This advance enables accurate reconstruction of complex quantum systems even when limited measurements are available. The technique characterises quantum systems, the fundamental building blocks of future computers, using fewer computational resources than before. It compresses how information about a…