Quantum physicists in Johannesburg found a way to lock in quantum information, protecting it from outside noise

Experiments show that a structure in light keeps information intact even as usual entanglement measures fade.

The work was led by Andrew Forbes, a physicist at the University of the Witwatersrand (Wits). His research focuses on structured light, beams engineered with tailored shapes and polarization, to control quantum states of photons.

Qubits and skyrmions

In most quantum devices, qubits lose their delicate state very quickly. Stray photons, detector imperfections, and tiny vibrations all act as noise that scrambles the fragile quantum correlations that computers and networks depend on.

This work tackles the old problem that quantum entanglement, a tight link between distant particles, collapses as soon as real-world noise creeps in.

In the new study, the team tested six states with skyrmion numbers ranging from negative three to positive three by gradually increasing the noise.

Large quantum networks, systems that share entangled particles across many nodes, are being explored for ultra-secure communication and new kinds of sensing.

A recent review notes that entanglement sits at the heart of quantum communication, repeaters, and future quantum internet proposals.

Most protection schemes try to keep the entanglement itself alive using complex error correction or elaborate control of the channel.

In practice, that strategy struggles once noise becomes strong, especially outside carefully shielded laboratories and inside long-distance links.

Information in skyrmion topologies

The Wits team turned to skyrmions, stable twisting patterns in a field that are labeled by whole number topological charges.

Changing random details of a skyrmion does not easily change that integer label, which makes these patterns natural candidates for noise-resistant encoding.

One work on optical skyrmions shows that they can be generated and tuned with stability in lab devices.

The new results extend that idea to entangled photons, turning skyrmions into a discrete label for the shared quantum state.

Each pattern comes with a skyrmion number, an integer that counts how many times one sphere of states wraps another.

Because that number can only jump between whole values, the team describes their approach as a kind of digitization of quantum information.

Skyrmions and outside noise

To test the idea, the researchers created pairs of entangled photons whose spatial patterns and polarizations together encoded a nonlocal skyrmion.

The shared pattern gave the two-particle system a skyrmion number, so measuring one photon mapped out the space of the other.

They then subjected the photons to isotropic noise, which is a model where kinds of random disturbances are mimicked by mixing in a maximally scrambled state.

As they dialed up the noise, measures of entanglement purity, concurrence, and fidelity dropped toward the values expected for a mixed state.

Remarkably, the skyrmion number stayed fixed across almost all noise levels, changing only when the photons reached a maximally mixed, fully disentangled state.

Because the relevant observable is topological, many noise contributions cancel out when the team subtracts matched measurement outcomes that contain the same background.

Their equations show that noise only rescales the state space while preserving its wrapping, so the skyrmion number remains unchanged until entanglement vanishes.

Digitizing entanglement for real devices

One striking idea in the paper is digitized entanglement, a way of turning continuous quantum correlations into discrete, countable values.

Instead of relying on how strong the entanglement is, the scheme cares only about which integer skyrmion number is present.

“Topology is a powerful resource for information encoding in the presence of noise,” said Forbes.

He points out that the topological alphabet can be large, giving many distinct codes that remain readable as long as some entanglement survives.

An article links this resilience to quantum computers, global networks, imaging systems, and artificial intelligence tools that rely on entanglement.

Next steps for topological qubits

In noisy photonic chips and free-space links, information that rides on a discrete topological label could buy precious robustness without extra hardware overhead.

Future architectures might combine topological coding with conventional error correction, using each approach to cover different kinds of faults that appear in quantum processors.

For communication over distances, topologically encoded light could keep channels usable under daylight background, imperfect pointing, and detectors that would normally destroy quantum correlations.

That capability would be especially helpful in hybrid networks that mix fibers, drones, aircraft, and satellites into a single stitched-together quantum internet.

The conceptual advance is to encode quantity into a topological code built from entanglement, instead of trying to keep details of the state intact.

Once that perspective spreads into device design, the generation of qubits may worry less about being perfect and more about carrying topological addresses.

The study is published in Nature.

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