Qscale Quantum technologies for extending the range of quantum communications

The project

QScale is a European research project, funded by the CHIST-ERA coordination. Bringing together five academic partners from five different countries as well as one industrial partner, it aims at breakthrough research and innovation in the field of quantum information science.

Specifically, QScale is devoted to the development of advanced quantum communication technologies, in particular of quantum repeater architectures, which represent a major and timely challenge for the field of quantum information science and technology.

Quantum repeaters are needed in order to overcome losses and errors in the transmission of quantum data. It allows the distribution of entanglement at arbitrary large distances, which is a universal resource for quantum information applications, including quantum cryptography and quantum teleportation. At present, quantum repeaters constitute a well-identified milestone on the quantum technology roadmaps.

Organization and Workplan

The project is organized along 4 work packages, where all the partners are involved :

Workpackage organization of the project (click to enlarge)


The field of quantum information science and technology has emerged over the last two decades driven by the prospect to exploit capabilities from the quantum realm to accomplish tasks difficult or even impossible with traditional methods of information processing. In this broad context, quantum communication, the art of transferring a quantum state from one place to another, is one of the main streams of research. It led for instance to the demonstration of quantum cryptography, an unconditionally secure way to transmit information, and even to commercially available quantum key distribution systems and a full scale network physically deployed in a metropolitan area. However, the distance on which such protocols can be performed is limited by unavoidable transmission losses. Furthermore, the no-cloning theorem prevents from any amplification of the quantum signal as usually done in traditional communication lines. Reaching long-distance is thus a grand challenge for quantum communication and requires innovative concepts and components.

A quantum repeater node for efficient entanglement distribution : entanglement is distributed along two elementary segments, stored in quantum memories, and then exchanged by entanglement swapping operations.The concept of quantum repeater provides a solution. It consists in dividing the long distance in various shorter segments on which entanglement can be faithfully distributed. Adjacent segments are then connected by entanglement swapping operations. Crucial to this endeavour are quantum memories, which enable the storage of entanglement on each segment before proceeding to the connections. The concept of quantum repeater has become central to quantum communication but it represents a very challenging experimental and conceptual tour de force to design realistic and efficient architectures.

Objectives of the project

A cold atomic cloud, a single ion trap and a rare earth doped crystal : different systems that will be investigated as potential implementations of an efficient and long-lived quantum memory for non-classical lightThe objectives of the QScale project are to experimentally demonstrate photonic and atomic components enabling the development of quantum repeaters and their integration into quantum communication and processing networks.

The project addresses various kinds of photonic carriers and of material systems involved in quantum information : discrete variables based on single photons, continuous-variables which rely on quadrature components of light, ensemble-based memory devices or strings of trapped ions. The project tackles also the promising hybrid approaches where both carriers are mixed, leading to non-Gaussian processing tasks. These three different implementations will be compared.

Start date : September 1st, 2011
Duration  : 36 months