A tiny microchip has huge potential for the future of secure quantum communications. A new client-server quantum key distribution method developed at the University of Bristol allows quantum cryptography technology to be integrated onto an optical chip and installed in a mobile phone. This enables exchange of quantum information through an unstable environment, without the need for large, expensive technology limited to a fixed location, for example, a server room in a bank. In the study, large resources such as lasers and detectors were situated at the server site, which is accessible via telecom fiber to a client. This requires an on-chip polarization rotator, which may be integrated into a handheld device. “With much attention currently focused on privacy and information security, people are looking to quantum cryptography as a solution since its security is guaranteed by the laws of physics,” said Dr. Anthony Laing, a research fellow at the Centre for Quantum Photonics at the University of Bristol. The new technique uses photons as the information carrier and relies on integrated quantum circuits developed at Bristol. These tiny microchips are crucial for the widespread adoption of secure quantum communications technologies. This could pave the way for more secure mobile banking, online commerce and information exchange, according to the researchers. “Our work shows that quantum cryptography need not be limited to large corporations, but could be made available to members of the general public,” Laing said. “The next step is to take our scheme out of the lab and deploy it in a real communications network." The work was funded by the Engineering and Physical Sciences Research Council, the European Research Council, QuanTip, Phorbitec, and the Centre for Nanoscience and Quantum Information. The research is published in Physical Review Letters (doi: 10.1103/PhysRevLett.112.130501). For more information, visit: www.bristol.ac.uk