Entanglement swapping establishes the core capability of quantum communication by allowing networks to expand beyond simple point-to-point communication. It relies on quantum teleportation – a method where the quantum state of a particle can be transferred without having to move the particle itself across the distance. In entanglement swapping, teleportation occurs between two entangled photon pairs, resulting in a shared state between particles that have never interacted.
This ethereal concept – which understandably makes sense to very few people – is what Albert Einstein famously referred to as “spooky action at a distance.” It underscores the unique nature of quantum mechanics which is generally not observable in our day-to-day lives.
By demonstrating entanglement swapping, we can create a scalable network where quantum information can be transmitted over vast distances, something currently limited by decoherence (the degradation of quantum information caused by external factors) and loss (where a portion of the transmitted quantum information does not reach the receiver). This advancement is crucial for global quantum networks that could connect any two points on Earth with high security and reliability.
Why space?
Establishing a quantum network requires the efficient routing of quantum information. Local quantum networks at the scale of buildings, campuses, or even cities are effectively implemented using fiber-optic networks. Extending the reach of a quantum network to regional, national, or global scales is limited by the transmission loss across the network. At a threshold of a few hundred kilometers, the losses in fiber-optics are greater than losses in free-space-optical channels—it becomes more efficient to transmit quantum information between telescopes than across fiber-optic cable.
Airborne or orbital quantum networking nodes can extend the range of practical quantum networks. The higher the altitude, the wider the range of the quantum network. For these reasons, satellite-enabled quantum networks are viewed by the quantum networking community as a necessity for establishing a global quantum internet.
Entanglement Swapping in Space
Performing entanglement swapping, especially in space, involves overcoming significant technical hurdles. Quantum states are delicate, and maintaining entanglement through environmental factors like temperature and radiation presents added layers of complexity. The process requires precision engineering and first-of-its-kind technology to stabilize and sustain these states in a way that was previously thought to be impractical, if not impossible.
