April 16, 2025 -- HRL Laboratories and Boeing have completed construction and technical validation on a quantum communication subassembly for Boeing’s Q4S satellite mission – a first-of-its-kind effort to demonstrate four-photon quantum entanglement swapping in space. This powerful capability is essential to enabling future secure communications and distributed quantum networks.

With this milestone, HRL has successfully completed construction of the fully integrated, space-grade subassembly, a significant step toward flight readiness. The build brings together our optical board, control electronics and final thermo-mechanical packaging into a single, space-ready system. It has already passed initial end-to-end software verification.

“HRL has delivered an optical lab’s worth of capability in a compact, 15kg integrated space-capable assembly,” said Jay Lowell, Chief Scientist of Boeing’s Disruptive Computing, Networks & Sensors organization. “After validating the space qualification of our subassembly in our Boeing El Segundo Space Simulation Laboratory, this payload subassembly will serve as the ground twin to mirror the on-orbit payload which is currently in production.”

In validation tests, the team demonstrated quantum entanglement for each of the two sources in this subassembly.

“Demonstrating entanglement swapping between these two entangled photon pairs, will enable us to entangle previously unconnected nodes, a foundational breakthrough for building secure, scalable quantum computing and sensing networks in space,” said Jennifer Ellis, Principal Investigator at HRL.

1. To ensure reliable performance in orbit, the team rigorously tested the subassemblies of the single photon sources.
2. Each source performed well, showing strong signal quality (fidelity between 0.8 and 0.9) and detecting over 2,500 matching photon pairs per second, enough to meet the project’s requirements for accurate quantum measurements.

“Validation and environmental testing are critical milestones on the path to a successful space mission,” said Rob Vasquez, CEO of HRL. “We’re proud to partner with Boeing on this pioneering demonstration and lay the groundwork for secure communications in space.”