Quantum information: Sharing quantum secrets

A cost-effective architecture for quantum cryptography has been demonstrated in which a single receiver positioned at a network-hub node is shared by many end users to exchange secret encryption keys. See Letter p.69 Quantum key distribution (QKD) is a process allowing secure information exchange between a transmitter and receiver with access to both classical and quantum resources. Its use has been limited to niche applications in dedicated high-security networks, not least because it becomes extremely resource-intensive when multiple users require access to the system. Here, Bernd Frohlich et al. outline the principles of a new QKD system, termed a 'quantum access network', based on simple and cost-effective optical telecommunication technologies. They then demonstrate the concept experimentally in a 64-user network in which, for simplicity and economy, all users share a single photon detector placed at a key node in the network. The authors suggest that this advance could lead to the adoption of quantum technologies as routine in the secure transmission of data.