TECHNICAL
and precision. Local-scale networking (or transfer of state) is an enabler for scaling-up of quantum computers, to help realise the economic potential they offer. In the longer-term, we may expect to see quantum computers sharing information at longer distances to enable distribution of some tasks. For each of these applications, building the networking technology that enables the secure distribution of quantum state is a substantial challenge; a quantum- specific approach (combined with cyber security expertise) appears to be a natural fit. It is possible that the technologies underpinning QKD could play some part in future quantum networks. However, these technologies will be just one of a number that are needed to address broader network security challenges. The skills used to develop existing quantum communications technologies, as well as recent progress on assurance of quantum technologies, are likely to be relevant in meeting these challenges. This includes foundational research to develop and instantiate quantum network protocols, and engineering expertise to design and build the various components (such as quantum memories and repeaters) that will enable such functionality.
these cases, unpredictability is important, as is assurance in the behaviour of the random number generator. Classical RNGs have met these needs for many years, and continue to do so. Although they do not provide ‘perfect’ randomness, we know how to characterise their performance and condition the output to give the security guarantees we need. However, QRNGs have the potential to offer other properties that could be of value, in addition to ‘perfect randomness’. One important feature is the rate of generation. Quantum sources can – in theory – generate entropy at a significantly higher rate than classical sources. This could be useful in, for example, modern simulation algorithms. A second property is the ability to rapidly detect degradation of the source through precise modelling of the quantum components, something that classical sources do not routinely offer. In short, we are keen that research on QRNGs continues to progress. The NCSC would like to see a focus on the assurance of the raw sources, their integration into fully-engineered devices, and their role in larger, mostly classical systems.
Local-scale networking (or transfer of state) is an enabler for scaling-up of quantum computers, to help realise the economic potential they offer.
Closing thoughts
Quantum networking
The implementation of the National Quantum Strategy includes five missions. One of these includes the target that by 2035, the UK will have deployed the world’s most advanced quantum network at scale. A number of the planned outcomes of that mission focus on use cases described in this paper. We believe there is an ideal opportunity for industry and academic groups in the quantum communications and cyber security sectors to work in partnership to the benefit of the UK, with a focus on envisioning secure network architectures, defining the components that may be needed, and thinking about the assurance of these components and the wider system.
We have seen the term ‘quantum networking’ used to cover a range of possible future deployments of quantum communications technologies. Broadly, these fall into three classes.
1. Replacing classical security functionality with quantum
technologies. We can view QKD as an instance of this, replacing classical key generation and agreement with a quantum approach. 2. Extending classical networks to include new functionality that can only be provided by quantum components (for example, integrating quantum sensors into larger networks). 3. Inherently quantum networks, distributing entangled quantum states between quantum devices. The latter two of these have the most interesting applications. Entanglement between distant nodes of quantum sensor networks can provide greater sensitivity
www.ncsc.gov.uk
Volume 48 No.1 MARCH 2026
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