Quantum modulation of a coherent state with a single electron spin

Abstract

The interaction of quantum objects lies at the heart of fundamental quantum physics and is key to a wide range of quantum information technologies. Photon-quantum-emitter interactions are among the most widely studied. Two-qubit interactions are generally simplified into two quantum objects in static well-defined states. In this work we explore a fundamentally new dynamic type of spin-photon interaction. We demonstrate the modulation of a coherent narrowband laser by a coherently evolving spin in the ground state of a quantum dot. What results is a quantum modulation of the output phase (either 0 or π but no values in between), and a new quantum state of light that cannot be described lassically.