The story begins with a simple but bold idea. What if light could be shaped so precisely in space and time that it begins to carry information in ways nature never intended. Researchers from the School of Physics at Wits University, working with collaborators from the Universitat Autònoma de Barcelona, have now shown that this is no longer a distant dream. Their new review, published in Nature Photonics, reveals how quantum light can be engineered to create high-dimensional and multidimensional quantum states. In other words, photons can be sculpted like clay, and those sculpted forms could transform the future of quantum communication.
Structured photons are at the heart of this transformation. These are photons whose spatial, temporal, or spectral properties have been deliberately shaped. And the researchers argue that controlling these properties unlocks new pathways to carry enormous amounts of information securely and efficiently. But the story they tell is not just about new tricks of light. It is about a field that has grown from nearly empty shelves to a bustling workshop of tools, techniques, and possibilities.
A Toolkit That Went From Empty to Overflowing
Professor Andrew Forbes of Wits University, the corresponding author of the review, describes just how radically the field has shifted. “The tailoring of quantum states, where quantum light is engineered for a particular purpose, has gathered pace of late, finally starting to show its full potential. Twenty years ago, the toolkit for this was virtually empty. Today we have on-chip sources of quantum structured light that are compact and efficient, able to create and control quantum states.”
The article maps the rapid expansion of this toolkit. Techniques once scattered across specialized laboratories have converged into a coordinated ecosystem. On-chip integrated photonics makes it possible to generate quantum structured light in compact, scalable platforms. Nonlinear optics enables the creation of entangled or correlated photons with carefully designed properties. Multiplane light conversion allows light to be shaped across many dimensions at once. Each technique is powerful on its own, but together they form a modern, versatile set of tools for shaping quantum states with unprecedented precision.
This growing toolbox is not just impressive; it is practical. With it, structured quantum states are becoming suitable for real-world applications in imaging, sensing, and communication networks. Every advance pushes them a little closer to everyday technology.
The Promise Hidden Inside High Dimensions
At the center of this progress is the remarkable advantage gained by structuring photons. When photons are shaped, they can carry information using high-dimensional alphabets. Instead of encoding data in a simple yes-or-no, one-or-zero binary system, each photon can represent many states simultaneously. This means more information per photon and greater resilience to noise—two ingredients that make quantum communication far more powerful.
Structured light offers a particularly enticing route for secure communication technologies. By using high-dimensional encoding, quantum messages can be made more robust against interception or interference. With every added dimension, security grows stronger and data capacity expands.
But the story is not without obstacles.
The Trouble With the Journey Through Space
For all its promise, structured light faces the challenge of traveling long distances through real-world environments. The researchers point out that some natural channels simply do not cooperate. Turbulent air, imperfections in fibers, and environmental noise can distort spatially structured photons, limiting how far they can travel compared to more familiar degrees of freedom such as polarization.
Forbes puts it plainly. “Although we have made amazing progress, there are still challenging issues. The distance reach with structured light, both classical and quantum, remains very low … but this is also an opportunity, stimulating the search for more abstract degrees of freedom to exploit.”
This is where the narrative takes an unexpected turn. Instead of fighting against environmental imperfections, researchers are looking for states of light that naturally resist them.
When Quantum States Become Topological
One of the most intriguing future directions described in the review involves giving quantum states topological properties. Topological states are known for their ability to survive disturbances that would normally destroy fragile quantum information. The authors suggest that this could offer a path toward inherently robust quantum technologies.
Forbes explains the potential. “We have recently shown how quantum wave functions naturally have the potential to be topological, and this promises the preservation of quantum information even if the entanglement is fragile.”
This idea could change everything. If quantum states can be encoded in their topology rather than their precise spatial shape, they may remain stable even in messy, noisy environments. It is a strategy borrowed from nature itself, where topology often provides resilience in physical systems.
Racing Into Multidimensional Futures
Beyond topology, the review highlights an entire landscape of accelerating developments. Multidimensional entanglement is now being explored with increasing sophistication. Ultrafast temporal structuring lets researchers carve light into patterns that unfold over trillionths of a second. Nonlinear quantum detection schemes allow scientists to observe quantum states that once seemed impossible to witness directly. And on-chip sources continue to push the boundaries of what can be generated or processed in higher dimensions.
These advances feed directly into applications that feel like previews of future technology. High-resolution quantum imaging promises sharper, more sensitive pictures than classical systems. Precision metrology using structured photons could help measure tiny changes in physical systems with extraordinary accuracy. And quantum networks built on multidimensional light may one day carry far more information than any network in existence today, with channels that intertwine like threads in a vast quantum tapestry.
The review paints a picture of a field on the verge of transformation. Recent progress is not incremental. It is exponential.
Why This Matters
In the final lines of the review, the authors write that the future for quantum optics with structured light “looks very bright indeed”. Yet they are clear-eyed about what must still come next. Increasing dimensionality, boosting photon numbers, and designing states that can survive the imperfections of realistic environments remain crucial steps.
The importance of this research reaches far beyond academic curiosity. Structured quantum light could form the backbone of secure communication networks, transformative imaging systems, and quantum sensors capable of detecting phenomena that classical tools cannot. It represents a shift from understanding light to sculpting it and from observing quantum behavior to designing it.
As the field steps into this new era, it carries the promise of technologies that not only communicate more information but do so with resilience, precision, and elegance. And it all begins with a simple question that the researchers at Wits University and the Universitat Autònoma de Barcelona are helping to answer. What can light become when we learn to shape it in every dimension of space and time?
More information: Andrew Forbes et al, Progress in quantum structured light, Nature Photonics (2025). DOI: 10.1038/s41566-025-01795-x
