An international team of researchers led by the Friedrich Schiller University Jena has proposed a method to generate entangled photon pairs using 2D materials. The advance could open the door to quantum encryption on mobile devices. The work presented a greatly miniaturized source for entangled photon pairs in a stacked transition metal dichalcogenide crystal, measuring 10 × 10 × 10 µm, allowing it to be easily integrated into compact devices. The crystal symmetry enables the generation of polarization-entangled Bell states without additional components. The device presents significant advantages over conventional sources for entangled photons, which can be bulky and complex to handle. The source also provides tunability by simple control of the pump polarization. Generation rate and state tuning are decoupled, leading to equal generation efficiency and no loss of entanglement. According to research led by the Friedrich Schiller University Jena, the combination of transition metal dichalcogenides with monolithic cavities and integrated photonic circuitry or using quasi-phase matching could provide an avenue toward ultrasmall and scalable quantum devices. Courtesy of Fraunhofer IOF/Christian Süß. That flexibility opens a wide range of potential applications, particularly in the field of quantum communication and quantum encryption. Mobile devices could benefit from the technology in the future by providing secure communication channels based on the principles of quantum mechanics. Creation of entangled photon pairs on such a small scale and with tunable properties could have far-reaching implications for the development of quantum computers and quantum communication systems. For mobile communication and portable devices in particular, this opens up a new field that has so far remained untapped because of the size and complexity of the technology required. The results of this research mark a significant step towards practical applications of quantum optics and could form the basis for future developments in secure data transmission. Future work on the project will focus on increasing the generation rate by quasi-phase matching and integration of the source into monolithic cavities with high quality in order to improve the pair generation rate. The integration of these sources into photonic chips will also be explored to develop quantum key distribution devices in miniature. In addition, the team plans to investigate the use of novel materials and metasurfaces to create even brighter and more versatile sources. The work occurred under the auspices of the international research training group 2675 “Meta-Active” and was led by Maximilian Weißflog at the Friedrich Schiller University Jena with participation from the Australian National University in Canberra and contributions from the Technical University of Darmstadt. The research was published in Nature (www.doi.org/10.1038/s41467-024-51843-3).