Rendering of a Q4S Satellite Containing Entanglement Swapping Device. Credit:Boeing

One of the key components that will be needed in a future quantum internet is a device that performs a process known as entanglement swapping. This is a device can start with two pairs of entangled photons and swaps the entanglement such that a photon from the first pair becomes entangled with a photon from the second pair. As an example, in the diagram below, the process starts with Photon 1 entangled with Photon 2 and also Photon 3 entangled with Photon 4. By performing a Bell State Measurement between Photons 2 and 3, the entanglements will be swapped and Photons 1 and 4 will be entangled with each other.

Entanglement swapping is a critical technology for extending the span of a quantum network. Due to the fundamental laws of quantum physics, a classical optical repeater can’t be used to regenerate a qubit as it travels through a network. Using a quantum repeater will provide an alternate way of solving the problem without violating the laws of quantum physics.

Boeing along with partner HRL Laboratories have been working on developing such a device and plan to launch it in a sun-synchronous orbit in a satellite called Q4S, approximately 550 kilometers above Earth. The purpose is to demonstrate the technology and show how such a device can be built such that it is space hardened and can survive the extreme environment including the shock, vibration, radiation, temperatures involved with a device launched into space. A schematic diagram of the device is pictured below and its size is approximately 40 x 30 x 30 centimeters. The companies will be operating and testing the device remotely to see how it performs.

Schematic Diagram of the Boeing/HRL Entanglement Swapping Device. Credit Boeing

Boeing has a future vision of a quantum internet base upon satellites that use these types of devices. Such a network has a great many possible use cases in the future as discussed in GQI’s Quantum Safe report. However, a great many more components need to be developed to withstand the harsh environment of space including photon sources, photon detectors, quantum, memories, etc.

Boeing Vision of a Future Quantum Internet Using Satellites. Credit: Boeing

For additional information about this effort, you can access a press release posted by Boeing here and a web page for the Q4S project here.

September 10, 2024