10142737QWRTY2 (Quantum-enhanced White Rabbit Time transfer sYstem step 2)ActiveCollaborative R&DInnovate UKWhite Rabbit (WR) is a GNSS-independent, Ethernet-based technology for time distribution over optical fibre. Originally developed by CERN (European Organisation for Nuclear Research) for particle physics experiments, WR is gradually being used by other applications such as comparison of distant atomic clocks, synchronisation of antenna arrays in radio-telescopes, and accurate time-stamping of transactions in the stock exchange, to mention just a few. WR provides sub-nanosecond accuracy and picosecond precision, making it ideal for synchronising large distributed systems. The latest official version in production of the WR Switch is v3.4, sold by vendors in Spain, The Netherlands, Poland, and China. GMV-UK is currently developing the new version of the WR Switch (v4), which includes significant improvements, notably an expansion board to provide enhanced functionalities. Our expansion board integrates a Rubidium chip-scale atomic clock (CSAC) utilising quantum Coherent Population Trap (CPT) to achieve a highly stable frequency and excellent holdover capabilities. Holdover is the capacity of a clock to maintain accurate time when its synchronisation source is disrupted or temporarily unavailable. Therefore, with GMV-UK's WR Switch, we aim to boost the resilience of the UK Critical National Infrastructures (CNI) by maintaining a bounded time error in holdover during distressed conditions until the link is restored. A widely adopted requirement (e.g., telecom) is not to exceed 1.5 microseconds after 24 hours. The objective of this project is to accelerate the commercialisation of GMV-UK's WR Switch with holdover capabilities, demonstrating GMV-UK's potential to provide resilient time and frequency solutions for a number of markets and applications where precision time and frequency synchronisation is critical. The project is led by GMV-UK, in collaboration with IQD and the National Physical Laboratory (NPL). GMV-UK specialises in advanced systems for space, position, navigation, timing (PNT), and robotics. IQD is a market leader in frequency products, offering solutions ranging from low-cost commercial-grade to high-reliability industrial and automotive applications. NPL operates the national time scale UTC(NPL) and leads the National Timing Centre (NTC) programme, focused on providing resilient time across the UK. This collaboration ensures that a UK system integrator, clock provider, and end user work together to deliver a fully functional PNT product with advanced quantum-enabled features that meets UK market needs.