In a groundbreaking advancement that could redefine the future of quantum communications, researchers at the University of Technology Sydney (UTS) have demonstrated through computational modeling that entangled photons, fundamental to quantum information transfer, can be reliably sent from Earth’s surface up to orbiting satellites. This uplink transmission method marks a significant departure from the existing paradigm in quantum satellite communications, which predominantly relies on downlink approaches, wherein quantum signals are generated aboard the satellite and transmitted downward to ground stations. Contrary to previous assumptions that atmospheric interference and signal loss would render uplink methods impractical, the new study reveals that these challenges can be effectively mitigated, opening the path for more powerful and scalable quantum networks leveraging low Earth orbit satellites.
Since the launch of China’s Micius satellite in 2016, quantum satellite communications have predominantly operated on the principle of creating entangled pairs of photons in space and distributing each half to disparate ground stations. This so-called “downlink” strategy has been pivotal in demonstrating the feasibility of ultra-secure quantum cryptographic key exchange over vast distances. More recently, entities like the Jinan-1 microsatellite have extended these quantum links over continental scales, such as a remarkable 12,900 km connection between China and South Africa in 2025. However, the downlink method inherently restricts signal strength and flexibility, given that satellites are constrained by size, power, and maintenance challenges while orbiting hundreds of kilometers above Earth.
The UTS research team, led by Professors Simon Devitt and Alexander Solntsev, has taken an innovative approach by reversing the quantum transmission direction. They considered the possibility that ground-based stations, with the advantage of greater power availability, easier maintenance, and potentially stronger photon sources, could emit entangled photons upward towards distant satellites. This uplink concept was long dismissed due to anticipated complications such as scattered photons, atmospheric turbulence, background solar and lunar reflections, and the high relative velocity of satellites, traveling approximately 20,000 km per hour in low Earth orbit.
Through meticulous computational modeling that accounted for real-world environmental variables—like atmospheric absorption, Rayleigh scattering, sky brightness influenced by sunlight, moonlight reflections, and optical system misalignment—the UTS team found that the uplink transmission of entangled photon pairs remains feasible. Their simulations described scenarios where two separate ground stations simultaneously fire individual entangled photons toward a satellite 500 km above Earth, precisely timed such that these photons coincide and interfere quantum mechanically on board the satellite. This interference is essential to preserve entanglement correlations critical for quantum information processing and cryptographic security protocols.
One of the most transformative revelations from this research is the practical implication for creating high-bandwidth quantum communication channels. Quantum internet applications, particularly those linking quantum computers, demand the transmission of orders of magnitude more photons than conventional cryptographic systems. Satellites equipped with complex photon sources capable of generating massive photon streams are impractical due to power, size, and cost restrictions. Instead, offloading photon generation to ground stations, enabling uplink transmission, means satellites only require lightweight, compact optical detectors and interference units that register incoming signals and relay results back to Earth.
This shift effectively reduces satellite payload complexity and operational expense, making the entire quantum network infrastructure more scalable and maintainable. Ground stations have the flexibility to upgrade photon sources independently of satellite hardware, potentially allowing continuous improvement of quantum network throughput and reliability. The strategy also introduces design versatility for constellations of small, low Earth orbit satellites that can collectively provide global quantum entanglement coverage by interlinking with multiple terrestrial uplink points.
The researchers highlight that while the basic physics of quantum entanglement distribution remains consistent, engineering uplink channels involves managing environmental noise and maintaining alignment precision over vast distances and rapidly moving orbital platforms. Their models incorporated sophisticated error sources, from atmospheric turbulence altering beam propagation to solar background light competing with single-photon detection events. The success of these simulations inspires confidence that physical demonstrations of uplink quantum links can be achieved imminently, possibly through experimental setups on drones or stratospheric balloon receivers before progressing to full satellite trials.
Looking ahead, the team envisions a future quantum internet where entanglement distribution becomes a ubiquitous utility, analogous to how electricity powers everyday devices invisibly. Quantum entanglement could be commoditized, available on demand as an infrastructure service to quantum computers and devices requiring secure, instantaneous correlations. Users would interact seamlessly with quantum networks by “plugging in” their devices to entanglement sources, much as we do with power grids today, enabling revolutionary applications in cryptography, distributed computing, and sensing.
The interdisciplinary nature of this project, blending expertise in quantum photonics, information theory, atmospheric physics, and network engineering from UTS faculties, underscores the complexity and innovation required to overcome quantum satellite communication challenges. This study not only challenges previous assumptions about the limitations of uplink quantum channels but also paves the way for the next generation of quantum communications, integrating space-based platforms with ground infrastructure to accelerate the global rollout of secure quantum networks.
These findings emphasize that the future of quantum communication will likely be hybrid, leveraging both uplink and downlink architectures optimized for specific applications and environmental constraints. Realizing practical uplink quantum satellite channels represents a paradigm shift, enabling higher performance, lower cost, and more adaptable quantum networks that could eventually underpin a worldwide quantum internet, further pushing the boundaries of both science and technology.
As the work transitions from theoretical and computational studies to experimental validation, the anticipation grows for demonstrations that could transform quantum satellite communications. The deployment of test platforms on drones or balloon systems will validate the robust quantum interference signals predicted by simulation, building essential confidence for space missions incorporating uplink communication capabilities. Such practical verification will be a critical milestone towards realizing a quantum internet that spans continents, ensuring secure and resilient communication networks unmatched by classical technologies.
In summary, the UTS study published in Physical Review Research thoroughly reevaluates the feasibility of sending entangled photons from ground-based sources upward to satellites, overcoming longstanding technical hurdles. It offers a vision for a scalable, high-capacity quantum communications infrastructure supported by uplink transmission methods, which until now remained theoretical and largely dismissed. By harnessing computational simulations backed by realistic environmental parameters, this research ushers in transformative possibilities for quantum networking and cryptographic systems, cementing the role of quantum satellites as pivotal enablers of the emergent quantum information era.
Subject of Research: Not applicable
Article Title: Quantum entanglement distribution via uplink satellite channels
News Publication Date: 14-Oct-2025
Web References:
https://journals.aps.org/prresearch/abstract/10.1103/v3p1-kz4h
http://dx.doi.org/10.1103/v3p1-kz4h
References:
Devitt, S., Solntsev, A., et al. (2025). Quantum entanglement distribution via uplink satellite channels. Physical Review Research.
Keywords:
Quantum satellite communications, uplink entanglement distribution, quantum interference, entangled photons, quantum internet, low Earth orbit satellites, quantum cryptography, quantum networking, photon transmission, atmospheric modeling, computational simulations, quantum photonics.
