All-optical storage of phase-sensitive quantum states of light

TL;DR

This paper demonstrates the first all-optical storage and retrieval of phase-sensitive quantum states of light, enabling advanced quantum information processing with nonclassical states.

Contribution

Introduces a phase-probing mechanism for storing phase-sensitive quantum states in concatenated optical cavities, extending previous phase-insensitive storage methods.

Findings

Successfully stored and released phase-sensitive superposition states

Observed negativity in Wigner function after storage, confirming nonclassicality

Demonstrated potential for storing more complex quantum states

Abstract

We experimentally demonstrate storage and on-demand release of phase-sensitive, photon-number superposition states of the form $\alpha |0\rangle + \beta e^{i\theta} |1\rangle$ for an optical quantized oscillator mode. For this purpose, we introduce a phase-probing mechanism to a storage system composed of two concatenated optical cavities, which was previously employed for storage of phase-insensitive single-photon states [Phys. Rev. X 3, 041028 (2013)]. This is the first demonstration of all-optically storing highly nonclassical and phase-sensitive quantum states of light. The strong nonclassicality of the states after storage becomes manifest as a negative region in the corresponding Wigner function shifted away from the origin in phase space. This negativity is otherwise, without the phase information of the memory system, unobtainable. While our scheme includes the possibility of optical storage, on-demand release and synchronization of arbitrary single-rail qubit states, it is not limited to such states. In fact, our technique is extendible to more general phase-sensitive states such as multiphoton superposition or entangled states, and thus it represents a significant step toward advanced optical quantum information processing, where highly non-classical states are utilized as resources.