Engineering Quantum Emitters for Integrated Quantum Networks

Georgios M. Nikolopoulos, Thomas Brougham, Antonín Hoskovec +1 more

David J. Starling, Katia Shtyrkova, Ian Christen +13 more

Realizing a quantum network will require long-lived quantum memories with optical interfaces incorporated into a scalable architecture. Color-center quantum emitters in diamond have emerged as a promising memory modality due to their optical properties and compatibility with scalable integration. However, developing a scalable color-center emitter module requires significant advances in the areas of heterogeneous integration and cryogenically compatible packaging. Here we report on a cryogenically stable and network compatible quantum emitter module for memory use. This quantum emitter module is a significant development towards advanced quantum networking applications such as distributed sensing and processing.

Oliver Dudgeon

Nitin Jha, Abhishek Parakh, Mahadevan Subramaniam

Abstract Quantum key distribution (QKD) will most likely be an integral part of any practical quantum network setup in the future. However, not all QKD protocols can be used in today's networks because of the lack of single photon emitters and noisy intermediate quantum hardware. Attenuated photon transmission typically used to simulate single photon emitters severely limits the achievable transmission distances and the integration of QKD into existing classical networks that use tens of thousands of photons per bit of transmission. Furthermore, it has been found that different protocols perform differently in different network topologies. In order to remove the reliance of QKD on single photon emitters and increase transmission distances, it is worthwhile exploring QKD protocols that do not rely on single-photon transmissions for security, such as the 3-stage QKD protocol; the 3-stage protocol can tolerate multiple photons in each burst without leakage of information. This paper compares and contrasts the 3-stage QKD protocol and its efficiency in different network topologies and conditions. Further, we establish a mathematical relationship between achievable key rates for increasing transmission distances in various topologies. Our results provide insight to a network engineer in designing QKD networks of the future.

Yinhui Kan, Shailesh Kumar, Xujing Liu +2 more

Entanglement between solid-state quantum emitters (QEs) is a key resource for photonic quantum technologies. Achieving such entanglement requires strong and controllable long-range interactions between QEs. However, engineering such coupling remains challenging, particularly for on-chip distant solid-state QEs. Here, we introduce a forward-designed platform that enables ultracompact nanophotonic architectures to mediate enhanced long-range QE-QE interactions via engineered surface plasmon polariton interference. Using this strategy, we realize two distinct configurations: a phase-conjugated elliptic design for energy funneling, and a co-radiating hyperbolic design for its suppression. We experimentally demonstrate large enhancement and suppression of energy transfer rates compared to bare substrates. Furthermore, we predict transient entanglement between spatially separated QEs with concurrence peaking at 0.493, approaching the theoretical bound in the transient regime. Extending to the multi-QE case, we observe enhanced energy funneling and predict QE-QE entanglement in three-QE configurations. These results establish a compact and scalable framework for on-chip entanglement engineering in integrated quantum nanophotonic systems.

Andrea Conti, Andrea Giani, Moe Z. Win