Cambridge quantum network

Abstract

Future-proofing current fibre networks with quantum key distribution (QKD) is an attractive approach to combat the ever growing breaches of data theft. To succeed, this approach must offer broadband transport of quantum keys, efficient quantum key delivery and seamless user interaction, all within the existing fibre network. However, quantum networks to date either require dark fibres and/or offer bit rates inadequate for serving a large number of users. Here we report a city wide high-speed metropolitan QKD network-the Cambridge quantum network-operating on fibres already populated with high-bandwidth data traffic. We implement a robust key delivery layer to demonstrate essential network operation, as well as enabling encryption of 100 Gigabit per second (Gbps) simultaneous data traffic with rapidly refreshed quantum keys. Network resilience against link disruption is supported by high-QKD link rates and network link redundancy. We reveal that such a metropolitan network can support tens of thousands of users with key rates in excess of 1 kilobit per second (kbps) per user. Our result hence demonstrates a clear path for implementing quantum security in metropolitan fibre networks.npj Quantum Information (2019) 5:101 ; https://doi.

Trusted Node QKD at an Electrical Utility

“…All switching and routing tasks are handled classically on the digitized measurement results. Trusted relay QKD, also known as trusted node QKD, has been realized in several demonstrations, starting with the DARPA Quantum Network [55], along with the SECOQC program [56], the Swissquantum network [57], the Tokyo quantum network [58], several quantum networks recently demonstrated in China [59]- [61], and the Cambridge quantum network [62]. In 2019, we completed the first steps to establish the feasibility of trusted relay QKD on a utility network using a single trusted location with a fiber loop-back [63].…”

40Gbits−1 Data Transmission in an Installed Optical Link Encrypted Using Physical Layer Security Seeded by Quantum Key Distribution

“…The implementation of privacy amplification used a number theoretic transform method. The security parameter for privacy amplification was 10 -10 which suggests that the key failure probability was 1 key failure every 30,000 years when the secure key rate is 1 Mbps with a block size of 100 Mbits [18]. The synchronisation and reconciliation channels were wavelength multiplexed onto the same fiber as the quantum channel.…”

“…A proof-of-principle experiment was demonstrated physical layer security in a 40G-Gbps coherent QPSK transmission system using a CW laser. The quantum key distribution element of this integrated system was demonstrated using a deployed link in the Cambridge Quantum Network [18]. The TDSPE system used the seed keys generated by the QKD system.…”

Experimental quantum conference key agreement

“…This key allows group-wide encryption for authenticated users to communicate securely, wherein, exclusively, members of the group can decrypt messages broadcast by any other member. Traditional two-party quantum key distribution (2QKD) primitives (2)(3)(4)(5) can be used to share N-1 individual key pairs between N users followed by classical computational steps to distill a conference key. However, this is inefficient for producing conference keys when users have access to a fully connected quantum network, as envisioned in the "quantum internet" (6,7).…”