Hidden symmetries enable transfer of quantum states

16 February 2026

Photo: AG Schmelcher

A latent symmetric network realized with laser-written optical waveguides. Although the network appears completely asymmetric, an analysis of the spectrum shows that the two points marked in red are latent symmetric. This latent or “hidden” symmetry enables efficient quantum state transfer between the two points.

Researchers at the Universities of Rostock and Hamburg have demonstrated for the first time that hidden symmetries can be used to transmit quantum states. In their experiments with a photonic system, they were able to prove that even in networks without recognizable geometric symmetry, quantum states can be transmitted reliably and precisely. The results pave the way for new secure methods of quantum communication and quantum cryptography. The work was published in the journal eLight in January 2026.

Symmetries are among the most powerful principles of order in nature. They determine not only the appearance of snowflakes and flowers, but also the fundamental interactions of particles and the physical laws that describe them. Well-known symmetries such as translation, rotation, or reflection are immediately apparent in the geometry of a system. However, not all symmetries are visible to the naked eye. Latent symmetry is a form of order that lies deeply hidden in the spectral properties of a system. Remarkably, a system in which latent symmetries occur can still behave symmetrically despite their invisibility. This allows the design of asymmetrical or even purely random systems that exhibit completely unexpected symmetry-driven properties and functionalities.

In their new publication, “State transfer in latent-symmetric networks,” physicists from the Universities of Rostock (Prof. Szameit's research group) and Hamburg (Prof. Schmelcher's research group) report on the first demonstration of quantum state transfer based on hidden symmetries. Using a network of laser-written optical waveguides, the researchers succeeded in constructing photonic circuits that possess this extraordinary property—or rather, cleverly conceal it—and make it usable for the transfer of nonclassical light states. Normally, light fed into a network at a single point spreads evenly across all nodes without symmetry. Jonas Himmel, doctoral student and first author of the study, explains: “Our system behaves in a very similar way – with one crucial exception: photons that are coupled in at a specific, inconspicuous point reappear almost as if by magic at a second such point.” This efficient coupling between two nodes in the network is made possible by the fact that both have the same “spectral fingerprint” – the characteristic feature of a latent symmetry.

By overcoming the dependence on conventional symmetries, the team has significantly expanded the design freedom for quantum circuits and opened up new perspectives for the development of secure quantum communication and quantum cryptography.

This research was funded by the German Research Foundation and the Alfried Krupp von Bohlen und Halbach Foundation.

Publication:

J. Himmel, M. Ehrhardt, M. Heinrich, T.A.W. Wolterink, S. Weidemann, M. Röntgen, P. Schmelcher and A. Szameit
"State transfer in latent-symmetric networks"
eLight Vol. 6, No. 3 (2026)