Can Quantum Technologies Solve the PNT problem?

Bottom Line Up Front:

Quantum technologies themselves will not solve the PNT problem, adopting a system engineering approach to the commercialisation of quantum technologies in the PNT domain is the best way to solve (test and verify) real user problems, to their satisfaction - the PNT problem.

What is the “PNT problem”?

The “Positioning Navigation and Timing (PNT) problem” refers to the challenge of providing accurate, available, trustable, reliable, and resilient positioning, navigation, and timing (including frequency) information for a wide range of applications, including transport, communications, power generation and distribution, finance, and national security (including our infrastructure). It can also be called “the problem of PNT resilience”.

Over the past two decades, more and more, PNT services supporting these critical infrastructure sectors are provided by Global Navigation Satellite Systems (GNSS), such as GPS, which use a constellation of orbiting satellites about 20,000 km above the ground, to broadcast sophisticated, but weak timing and positioning signals to ground-based receivers.

The problem part arises when these weak GNSS signals are disrupted or interfered with, either intentionally or unintentionally. For example, jamming and spoofing attacks can cause GNSS receivers to provide inaccurate or hazardously misleading information, obscuration or system failure can cause system outages. All of which can have serious consequences for transportation safety, financial transactions, power and utility safety, national security and so on. These are not theoretical incidences as examples of these disruptions exist.

Lack of PNT resilience is therefore a critical issue that affects a wide range of industries and applications; there is a growing recognition of the need to develop alternative, or more correctly, complementary sources of PNT (APNT or CPNT) information that are more resilient, trustable, and secure. This has led to increased investment in research and development of non-GNSS based PNT technologies, such as inertial navigation systems, radar and lidar-based positioning, and acoustic positioning systems, as well as quantum-based technologies.

Quantum-based technologies as defined here are those involving the control of individual or small numbers of atoms, resulting in phenomena such as superposition (the ability to be in multiple quantum states at the same moment) or entanglement (when two particles are linked together no matter how far apart they are).

They offer improved capabilities in navigation and time applications by more fidelity and precision in the determination of rotation, angular velocity, earth environment sensing, and time and frequency delivery.

What are the relevant quantum technologies?

There are several quantum technologies that are relevant for PNT, they can be summarised as:

1. Quantum clocks: The quantum properties of atoms can be used to keep time potentially with more accuracy than existing atomic clocks. These clocks can provide timing signals that are accurate to within a few billionths of a second, which could be used to improve the accuracy and the duration so that user PNT systems can continue to operate without GNSS. Of course, atomic clocks are used on GNSS satellites too.
2. Quantum sensors: The properties of quantum particles to detect changes in their environment can be used to measure acceleration and rotation with very high precision which has the potential to improve the operation and reliability of PNT systems, particularly in environments where GNSS signals may be disrupted or unavailable. The types of products are gyros, accelerometers, and gravity sensing systems (gravimeter/gradiometer). Gravity sensing (absolute and gradient) do not suffer from jamming and spoofing in the same way that GNSS does.
3. Quantum cryptography: The properties of quantum particles can ensure the security of communication and information exchange. This technology can be used to protect PNT information exchange from interference and spoofing attacks, which are a major threat to the reliability of GNSS-based systems.
4. Quantum imaging: The properties of entangled photons can be used to create images with very high resolution and sensitivity. This technology is often associated with medical imaging but can be used to improve the accuracy of remote sensing systems, which are used for navigation and mapping, as well as object detection.

Quantum technologies have the potential to improve PNT systems by providing more accurate, secure, and reliable information. While many of these technologies are still in research and development, they hold promise for improving the resilience of PNT systems in the face of growing threats and challenges. It is welcome that PNT is noted as a key area presenting market opportunities for the UK within the UK Quantum Strategy.

The UK’s Quantum Strategy

The UK's Quantum Strategy builds on an existing ten-year, ￡1 billion Quantum innovation and commercialisation programme launched in around 2015 and is a ten-year comprehensive and ambitious plan that aims to develop and deploy quantum technologies in a variety of areas, including PNT, through an investment of ￡2.5 billion over its ten years. The strategy recognises some of the potential risks to the availability and resilience of PNT information and seeks to develop alternative PNT technologies that improve resilience and security over existing techniques.

The strategy, some would say unusually for a government strategy, is a very motivational document to read. It includes excellent initiatives regarding the continuation of a network of quantum technology hubs, further bringing together academia, industry, and government to develop and commercialise quantum technologies; lots of focus and investment on skills, talent development and awareness of the application of quantum with a clear aim to demystify the technology away from a niche part of physics into the mainstream; as well as a written manifesto for tackling some of the associated big international and regulatory challenges. ?

The Quantum Strategy also challenges the Government to launch [funding] missions, including an already available mission in PNT (most welcome), and accelerator programmes to address commercialisation and manufacturing processes.

The success of the strategy will depend on a range of factors including the ability to attract investment, the development of viable commercial products and services, the ability to build a skilled workforce, and overcoming the joint (government and industry) challenge of getting products to customers at the right time, at the right price, with the right performance (the classic program management triple constraint).

However, many quantum technologies are still in the early stages of development (low-to-mid Technology Readiness Level (TRL)), so it will take some time (commonly quoted as 7-10 years) before they are widely deployed and integrated into existing PNT systems. So, in the meantime, it will be important for the UK and other countries to continue to explore complementary PNT sources, such as non-quantum based inertial navigation systems, radar, R-mode techniques, lidar-based positioning, terrestrial RF, and acoustic positioning systems, to ensure that critical infrastructure and services are not reliant on (or waiting for) a single technology or system.

Actions needed

Having stated that the UK Quantum Strategy is a positively motivational read, no strategy can cover every aspect of intervention and it is important to understand what a strategy does not prescribe. While the UK government approach can continue the collaboration and innovation across different sectors through the hubs, the success of these across the strategy duration will depend on them being innovation factories producing products and services that directly impact real world systems and services. The programme so far has attracted a significant amount of industrial and private investment with some spin outs, but the perception (right or wrong) is that these are academically not industrially focussed.

Additionally, as the strategy also challenges the quantum community to start to develop requirements and analyse the derived benefits, classical arguments however would say these should already have been done within the existing programme. Case studies, benefits and requirements work from within the existing programme could be publicised to crowd in support for the next ten years.

Money and money-related initiatives alone are not sufficient to support the growth of a sector or industry. It is fantastic to see the collaborative approach to outreach taken in the strategy and its plan, but a risk remains that quantum technology and PNT will remain niche, with user groups talking to trade bodies talking to centres of excellence, and insufficient attention to paying customers - unless there is a ruthless focus on the customer, on requirements, solving real problems, and demonstrating the accrued benefits thereof going forward. ?

The fundamentals of systems engineering practice tell us that it all starts with the Customers, understanding their needs, technology gaps, and concerns. At times, systems engineers must “imagine” what the customer’s voice is saying, so detailed understanding of use cases and needs is required.?Only by starting with needs, using them to derive requirements and specifications, and then developing compliant products and services, can satisfying solutions result.

Systems engineering approach.

Adopting a system engineering approach to help focus on specific users and specific use cases and the advantages associated with the adoption of quantum technologies within the PNT domain (and others) could help to accelerate their commercialisation.

While a system engineering approach involves taking a holistic view of a technology system, considering all its components, interactions, and constraints, and optimising the system for its intended purpose, its focus on specific customers and their unique needs can help to identify and enlist the support of communities of users with similar needs and concerns. In the context of quantum technologies for PNT, this would involve designing and optimising the entire PNT information delivery system, including the hardware, software, interfacing, testing, and validation to ensure that it meets the needs of its intended users for quality, availability, and resilience.

Existing techniques for testing and validation may not be suitable for performance/conformance measurement of quantum technologies, presenting new system engineering challenges.

Using customer oriented and initially solution agnostic systems engineering techniques helps to qualify and quantify the requirements that quantum technology developers can use to ensure that they optimise for commercialisation, focus on factors such as usability, scalability, reliability, and cost-effectiveness. This can also help to identify and address potential barriers, such as regulatory or export hurdles, intellectual property issues, or supply chain constraints (risks), but it can also help reveal initially unconsidered opportunities. This approach within the “quantum PNT ecosystem” can help to create a more collaborative and integrated approach to quantum technology development and commercialisation and supports the prevention of technology push or bias towards a particular technology or product.

It is not just about process junkies being satisfied in their work, or the development of “tools to monitor the development of tools” (a common accusation) – in the PNT world it means we can realistically and pragmatically answer the question “can quantum technologies solve the PNT problem?”. The answer I propose is “no, not fully”.

While quantum technologies can be a part of a solution, they are not the solution itself, although quantum technologies may be able to solve problems that we are not aware of yet.

The reason why is set out in several publications, but we can do worse than review Dr Paul Groves’ book “Principles of GNSS, Inertial, and Multi-sensor Integrated Navigation Systems”, which shows the need to consider not just parts of a whole, but the whole as well and the systematic error contribution from all parts of the PNT function – a system engineering approach. Quantum technologies have the potential to have a transformational impact on accuracy, precision, integrity, and the ability to operate for longer in GNSS denied environments – they offer a path to improvements, but they cannot solve the PNT problem overall.

For that, a return to the classical system engineering thinking that has powered invention and innovation is needed within the PNT system-of-systems. This will bring about the desired level of resiliency and more. Including quantum technology products within the PNT jigsaw would be prudent, using them where they add most value is the “sweet spot”. Systems engineering, by helping us to clearly understand the needs, will help us to better understand where the real value to communities of user’s can be found.

Integrating low-cost inertial sensors, high resolution 3D mapping (including gravity maps), hyper localised environmental understanding, the use of AI in decision making, and better clocks, oh and GNSS, will all be contributors to solving the PNT problem; we need to have all government and industrial strategies challenge us in these areas in the same way the Quantum Strategy challenges us to.

In this way we can measure success without changing direction!

Thanks to Bob Cockshott FRIN , Mitch Narins , and Paul Groves for supporting this.