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.
Highlights
Securing current network infrastructure has never been a more pressing issue
We demonstrate a 200 Gigabit per second (Gbps) encrypted link operating over the same fibre as quantum key distribution (QKD), which simultaneously consumes QKD keys for high-speed Advanced Encryption Standard (AES) encryption
The quantum channels of all systems operate on the International Telecommunication Union Dense Wavelength Division Multiplexing (DWDM) 100 GHz C-band grid[43] at wavelengths around 1550 nm and are multiplexed with the classical QKD reconciliation channels using standard wavelength spacing
Summary
Securing current network infrastructure has never been a more pressing issue. Accounts of breaches in personal and corporate data are frequently reported and the fall-out can be extremely damaging and costly to the parties involved.[1,2] Strengthening the security of networks that transport sensitive data is of paramount importance to mitigating the threat of data theft. Securing network data channels through the use of quantum cryptography[3,4] is a robust method of safeguarding data communications—the security of which derives from the laws of quantum mechanics. This security comes at a price: quantum states must in general be used to transport information and these carriers are extremely fragile. Previous approaches at building quantum networks have allocated additional dark fibres for quantum communication, distinct from the fibres carrying conventional data traffic.[5,6,7,8,9]
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