A quantum logic gate between a solid-state quantum bit and a photon

Abstract

Integrated nanophotonic devices create strong light–matter interactions that are important for the development of solid-state quantum networks1, distributed quantum computers2 and ultralow-power optoelectronics3,4. A key component for many of these applications is the photonic quantum logic gate, where the quantum state of a solid-state quantum bit (qubit) conditionally controls the state of a photonic qubit. These gates are crucial for the development of robust quantum networks5,6,7, non-destructive quantum measurements8,9 and strong photon–photon interactions10. Here, we experimentally realize a quantum logic gate between an optical photon and a solid-state qubit. The qubit is composed of a quantum dot strongly coupled to a nanocavity, which acts as a coherently controllable qubit system that conditionally flips the polarization of a photon on picosecond timescales, implementing a controlled-NOT gate. Our results represent an important step towards solid-state quantum networks and provide a versatile approach for probing quantum dot–photon interactions on ultrafast timescales. Researchers realize a quantum logic gate by performing all-optical coherent control of the exciton states of an InAs quantum dot in a photonic crystal cavity in the strong-coupling regime. Their demonstrations represent an important step towards realizing robust and scalable quantum networks and generating strong photon-photon interactions.