The most obvious, and most often discussed, doom scenario is based on the possibility of a quantum computer breaking existing cryptographic codes, enabling unauthorized access to protected information. If this happens, it may become easy for criminals to get unauthorized access to secure facilities, to implant malware or to disguise malware as software upgrades, etc. The most disruptive situations may occur if criminals or terrorists get access to vital facilities: energy plants, water supplies and water management, air and railroad traffic controls, etc. This can bring entire countries and economies close to a standstill for prolonged periods of time. Equally disruptive – although in a different way – is the situation where criminals or terrorists gain access to protected military or law enforcement information, enabling them to outsmart their opponents.

Money has become a digital asset and most banking transactions are done online. Economists estimate that less than 10% of all the money in the world exists as bank notes and coins. Cyber criminals targeting financial gains may use quantum technologies to hit financial networks and online banking: consider, for instance, primitive online theft at an excessive scale, that would render online banking transactions practically useless and thus seriously damage or completely cripple the modern banking system. In a similar way, unauthorized access can cause massive disruptions in the functioning of major banks and commodities/stock exchanges.

Rogue states or advanced terrorist groups might get access to blind quantum computing. Quantum computers are especially good at designing new materials and molecules – for good and for bad. Blind quantum computing services, accessed through 100% secure communication, can enable users to design new kinds of modern warfare, e.g. chemical or nuclear weapons, without anyone knowing about it, or use available large-scale computational facilities for advanced code breaking efforts. In a similar way, it may give terrorist groups or organizations, or rogue states, access to major military-oriented computational facilities to gain information about such development performed by other groups/countries, or possibly sabotage such computer-aided design and development.

Quantum technologies are being developed by big tech companies, research institutions and universities. Although findings from research done by universities are in the public domain, big tech companies often invest heavily in such research. As a result, big tech companies have early access to findings and can influence the focus of research to fit their own interest. Quantum technologies may provide many new opportunities in the areas of development of new materials and weapons, large-scale analysis of critical sensitive information and surveillance, secure communications, quantum-enabled computer sabotage, etc. Corporations may offer these new opportunities to governments in exchange for more favourable treatment, or for other political advantages, thus gaining too much political leverage. At the same time, the quantum technologies may make these corporations less amenable to conventional means of governmental and societal control.

Note that this may happen even without explicit bad intentions on the side of these corporations, simply in the normal course of legitimately pursuing new business advantages, seeking for better deals with the government, and ensuring a better position in the market. It may be too tempting for weaker governments to use tit-for-tat policies when dealing with such corporations, and surrender too much power to large businesses in exchange for short-term political gains. In the situation of strong international competition, some governments may even actively encourage this approach, hoping to exploit the quantum technologies offered by the corporations in order to advance their national or international political status.