Using quantum computing to design better bridges

Digital Catapult’s first Quantum Technology Access Programme (QTAP) raised awareness, educated end users, and fostered industry partnerships to drive the future adoption and commercialisation of quantum computing. During this first-of-a-kind programme, quantum experts from Digital Catapult and the programme partners ORCA Computing and Riverlane supported participants to explore novel quantum computing use cases.

Quantum computing for the built environment and construction sectors

Dedicated to sustainable development, Arup is a collective of designers, consultants and experts working globally in the built environment. Founded to be humane and excellent, Arup collaborates with its clients and partners using imagination, technology, and rigour to shape a better world. 

Arup has studied the potential applications of quantum computing in the built environment (Full report here) and found several areas in which it could be transformative such as optimisation of transport, logistics, energy and, in the longer-term, materials and decarbonisation challenges.

Quantum computing and bridge deck loading

During the Quantum Technology Access Programme (QTAP), Arup investigated quantum computing bridge design. It is important that a bridge is strong enough to support the expected load, but not so strong that it is over-engineered, wasting resources and money during construction. The aim was to find the maximum likely bridge deflection (movement) caused by vehicles crossing the bridge. At the QTAP showcase the Arup team explained that: “On a classical computer,  if you scale up, the difficulty of this problem increases massively and this equals time and operational cost” In the future quantum computers will solve these types of problems quicker than classical computers.

What was done?

The bridge deck loading problem is a combinatorial optimisation problem where the aim is to find the worst case combination of vehicles in different positions on a grid covering the bridge deck.  The bridge deflection depends on binary variables which encode different configurations of vehicles. The probability and length of each type of vehicle on the bridge were constrained, and a further constraint ensured that each position on the bridge could be occupied by at most one vehicle. The quantum boson sampler produced binary strings that were mapped to the relevant binary variables. The boson beam splitter angles were tuned classically to vary the output until the binary string corresponded to the worst case traffic configuration. Arup simulated a scaled down version of the problem and then ran it on the ORCA PT-1 photonics quantum computer using the ORCA Software Development Kit (SDK).

What was learnt?

Classical calculations verified that the correct solution was produced by both the simulation, and the real quantum computer, which is encouraging for future applications of this, and other algorithms, to the built environment and construction sectors. It is early days for quantum computing, and although classical methods are better at the moment, this is a promising line of research, particularly for problems such as the bridge loading problem, that are difficult, expensive or infeasible to tackle with classical computing technologies.  

The Arup team found it useful to learn about quantum computing by mapping the bridge deflection problem to an algorithm suitable for a quantum computer. Carrying out simulations and real runs on the ORCA SDK gave insight into the range of expertise needed to exploit quantum computing. The Arup team were “super excited to solve this [problem] on a real quantum computer” and benefited from access to ORCA Computing and Digital Catapult quantum experts.  Arup found it beneficial to learn about the strengths and weaknesses of quantum computing in the training and education arranged by Digital Catapult. Other participants’ use cases discussed during sessions organised by Digital Catapult inspired Arup to explore further applications.

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