Free space delay-line based optical buffer for quantum network

Optical quantum memories are essential components in numerous quantum information protocols, serving not only as storage devices but also facilitating a range of applications within quantum networks. However, the majority of current photonic quantum memories are matter-based and, while they offer impressive storage times, they suffer from key limitations such as narrow operational bandwidths, low input-output efficiency, and sensitivity to specific wavelengths and temperature.

In this work, we present a delay-line based, room-temperature, low-dispersion optical memory designed to address many of these challenges. The memory utilizes a pair of high-quality nested concave mirrors, offering a promising alternative for quantum memories. Our setup achieves a storage time of approximately 660 ns, with the ability to be reconfigured and extended through memory multiplexing, providing enhanced adaptability and control, while successfully preserving the polarization entanglement. Our approach represents a possibility toward practical, high-performance quantum memory solution, with wide-ranging implications for quantum networks and emerging quantum technologies.