Why Build Quantum Computers?

‘Quantum Computers are to classical computers what classical computers are to an abacus’.

Quantum logic represents an exponential increase in computational power compared to classical computers, for certain kinds of problems.

Quantum computers leverage the principles of quantum mechanics, such as superposition and entanglement. While a classical computer bit is either a 0 or 1, a quantum bit (qubit) can be both at once due to superposition, hence the exponential advantage. Entanglement, on the other hand, links qubits together, enabling complex computations.

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‘<…> four sectors—chemicals, life sciences, finance, and mobility—are likely to see the earliest impact from quantum computing and could gain up to $2 trillion by 2035’ — McKinsey

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‘<…> as it has done in the past with technologies such as semiconductors, the internet, and GPS, the public sector is providing substantial support through orders and grants.’

To date, government investors have committed a total of $57 billion to investments in quantum computing.

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Biology, health, and medicine

One of the most promising applications of quantum computers is in accurately simulating and understanding nature at the atomic scale. This has significant implications for understanding and designing new molecules, catalysts, enzymes, viruses, drugs. In drug discovery, the critical step is determining a molecule's electronic structure. Modelling the structure of a common drug like penicillin, which has 41 atoms at ground state, would require a classical computer with around 10^{86} bits—more transistors than there are atoms in the observable universe, making it physically impossible. However, a quantum computer with only 286 qubits could handle this task. Quantum computing also has applications in problems such as protein folding and drug design, which has led to initiatives such as pharmaceutical company Novo Nodirsk's Quantum Computing Programme and the collaboration between Accenture Labs and 1QBit with biotechnology company Biogen. Novo Nodirsk's holding company, Novo Holdings has committed €188M to supporting quantum technologies, including investing in quantum-focused VC Quantonation's latest venture fund and direct investment in the Series A round of Sparrow, a Danish photonic quantum computing company.

New materials and sustainability

Quantum computing is also expected to have significant implications in the design and development of new high-performance materials (ie IBM/Boeing collaboration on corrosion-resistant materials), hydrogen fuel cells (ie Azure Quantum and Johnson Matthey), battery materials (Microsoft/BASF) and catalysts (PhaseCraft; Quantinuum).

Several reports by groups such as McKinsey, PwC, andOxford Economics have discussed quantum computing's potential impact on and alignment with ESG initiatives and sustainability. These applications are reflected in the participation of sustainable investors in recent quantum startup fundraising rounds, such as Planet First Partners and ETF Partners investment in quantum error-correction scaleup Riverlane.

Large-scale optimisation problems of energy grids and financial models

Another impactful use case for quantum computers is solving large-scale optimisation problems, which every industry and company encounters in some form. These problems involve finding the best way to minimize or maximize a specific metric, often with billions of variables at play—too complex for classical algorithms to handle efficiently within a human lifetime. Quantum computers excel at addressing these challenges, managing the vast number of variables and complex interactions simultaneously. This makes them ideal for optimising global supply chains, energy grids, and much more.

This use-case of power grids has been the subject of collaborations between quantum computing companies and corporations such as Pasqal and EDF, Atom Computing and the US National Renewable Energy Laboratory and IonQ, Oak Ridge National Laboratory, and the US Department of Energy. Analyst firms such as Global Quantum Intelligence have released reports overviewing the applications of quantum computing in the energy sector for both near-term NISQ and future fault-tolerant quantum computing paradigms.

Factorisation and security

Probably the most famous application of all - a large quantum computer could be used to run Shor’s algorithm and factorise large numbers. The whole of our modern cybersecurity is based on the fact that factorising large numbers is a very hard problem for classical computers, and so the ability to suddenly do this in hours or days could jeopardise the world’s cybersecurity systems.

To counter this, NIST has recently published a set of standards for Post-Quantum Cryptography. These are Cryptographic codes that (as far as we know) do not yield to quantum computers. Nu Quantum notes that, because we now have a ‘buildable’ blueprint to build a Shor-capable machine, we have in our possession critical knowledge about timeline to ‘Q-day’.

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