Synthesis of antisymmetric spin exchange interaction and chiral spin clusters in superconducting circuits

• Da-Wei Wang, Chao Song, Wei Feng, Han Cai, Da Xu, Hui Deng, Hekang Li, Dongning Zheng, Xiaobo Zhu, H. Wang, Shi-Yao Zhu & Marlan O. Scully 

According to quantum mechanics, chiral states cannot be non-degenerate eingenstates of a parity-conserving Hamiltonian. This is in contradiction to the existence of chiral molecules—a fact known as as the Hund paradox1. The origin of molecular and biological chirality is conjectured to be related to parity-breaking interactions2,3 or environmental decoherence4, but a quantum superposition of two chiral molecular states with distinctive optical activities has never been observed5. To make progress in addressing these questions, it would be helpful to construct an artificial quantum system that breaks the parity symmetry and that can be prepared in a superposition of two chiral states. Here we report the synthesis of the parity-breaking antisymmetric spin exchange interaction in all-to-all connected superconducting circuits, which allows us to show various chiral spin dynamics in up to five-spin clusters. We also demonstrate the entanglement of up to five qubits in Greenberger–Horne–Zeilinger states based on a three-spin chiral logic gate. Our results are a step towards quantum simulation of magnetism with antisymmetric spin exhange interaction and quantum computation with chiral spin states.

Nature Physics 15, 382–386 (2019) 

The published article is available at http://doi.org/10.1038/s41567-018-0400-9