Researchers at U of T collaborated with Scientists at Quantum Bridge and Ki3 Photonics to develop a new framework to optimize the deterministic generation of photonic graph states—key resources for quantum sensing, communication, and computing. In principle, these states can be generated on-demand using emitters such as quantum dots, but the required interactions between quantum emitters are both noisy and experimentally challenging to implement. Minimizing the number of such interactions has long been a central challenge in the field.

In this study, the first author Sobhan Ghanbari et. al., introduce a novel optimization approach that reduces the number of quantum gates between emitters that are needed in the generation process. Rather than targeting a single fixed graph state, their algorithm considers all graphs locally equivalent to a target state in terms of non-local quantum correlations, called entanglement. By identifying patterns and correlations between graph properties and generation costs, the best candidate among the locally equivalent graphs can be determined. The method halves the number of interactions needed to produce an essential class of states in quantum communications, called repeater graph states. This advancement could enable the generation of larger and more complicated graph states, paving the way for quantum repeaters, better fault tolerance schemes, and the realization of a Quantum Internet.

More information here: https://arxiv.org/abs/2401.00635

More information here: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.052605