Configurable Entangled Photon Source for Quantum Networks

Quantum entanglement, a physical phenomenon in which two or more quantum systems share correlations even when separated by large distances, is an important resource for quantum information applications such as quantum computing and is critical for overcoming loss constraints that limit the transfer of quantum states across large distances. Despite their relative maturity in the field, entangled photon sources are still built primarily by graduate students, and there is significant variability among sources. Moreover, entangled photon sources lack flexibility, typically designed to output a single type of entangled state. We propose to develop a compact entangled photon source that can be programmed, or re-configured, to emit user-defined two- photon quantum entangled states (including both Bell states and non-maximally entangled states). The source design will be based on demonstrated entangled photon technologies and will incorporate feedback and optimization techniques that will enable the source to adapt to changing network conditions. The project will leverage Qubitekk’s expertise in developing and commercializing entangled photon sources for Quantum Key Distribution systems. The Phase I project demonstrated the feasibility of a configurable polarization entangled photon source by building an entangled photon source that can accommodate the control elements needed for full quantum state control and by identifying a set of control elements sufficient for accessing any two-photon polarization state. The functionality of those elements was tested experimentally and a simple optimization loop that adjusts the source in response to feedback from a reduced set of measurements was demonstrated. In Phase II, Qubitekk plans to advance the technology by incorporating the control elements into source designs that are more stable and reliable. In addition, Qubitekk will develop efficient feedback and optimization strategies that more closely target end-user device performance and that can adapt to changing quantum channel conditions. The goal of this project is to advance entangled photon source technology to provide connectivity between devices across a quantum network. This is likely to enable advances in a variety of quantum information applications, including quantum security and quantum sensing. In addition, the quantum information research community will benefit in the near term from the development of a versatile, configurable entangled photon source, as well as quantum state characterization technology.