Super-compact universal quantum logic gates with inverse-designed elements

Integrated quantum photonic circuit is a promising platform for the realization of quantum information processing in the future. To achieve the large-scale quantum photonic circuits, the applied quantum logic gates should be as small as possible for the high-density integration on chips. Here, we report the implementation of supercompact universal quantum logic gates on silicon chips by the method of inverse design. In particular, the fabricated controlled-NOT gate and Hadamard gate are both nearly a vacuum wavelength, being the smallest optical quantum gates reported up to now. We further design the quantum circuit by cascading these fundamental gates to perform arbitrary quantum processing, where the corresponding size is about several orders smaller than that of previous quantum photonic circuits. Our study paves the way for the realization of largescale quantum photonic chips with integrated sources and can have important applications in the field of quantum information processes.

Automated summary

Integrated quantum photonic circuit is a promising platform for future quantum information processing. To achieve large-scale quantum photonic circuits, the quantum logic gates applied should be as small as possible for high-density integration. In this study, supercompact universal quantum logic gates are implemented on silicon chips using the method of inverse design. The fabricated controlled-NOT gate and Hadamard gate are the smallest optical quantum gates reported so far. The designed quantum circuit, by cascading these fundamental gates, performs arbitrary quantum processing and is several orders smaller in size than previous quantum photonic circuits. This research paves the way for realizing large-scale quantum photonic chips with integrated sources, and can have important applications in the field of quantum information processing.