Quantum computing

*Updated version of the 2023 article.

Definition

There are problems that can be described mathematically but cannot be solved, despite the approaches to solving them being known in principle and proven to work. Some of these problems are unsolvable due to the sheer number of parameters. Other problems cannot be solved because solving them requires too many steps or generates memory-intensive intermediate results. Such problems can be found in a wide variety of disciplines: chemistry, pharmaceuticals or financial and actuarial mathematics. Quantum computing research exists because it has been repeatedly demonstrated that these systems are capable of solving some of these problems that cannot be solved today – by computing in a fundamentally different way to digital computers.  

Quantum computers harness quantum systems and their properties, which are described by quantum mechanics (the branch of physics concerning the behaviour of the smallest components of matter). The quantum realm operates under different laws than traditional mechanics, and much of it seems counterintuitive. Superposition is one of the properties that, when cleverly exploited, can make quantum computers more powerful than conventional computers. This is because, through state superposition, qubits can represent significantly more information than traditional bits.  

Quantum computers are now coupling many of these qubits in a controlled manner and in programmable sequences, generating complex quantum states that can then be used for computation. The fact that different solution paths can be calculated simultaneously is yet another important reason why quantum computers are far more efficient for certain mathematical problems than conventional computers.  

Current applications and opportunities

Quantum computers are still limited in terms of their practical usefulness. However, the current progress being made is significant, and the field is developing so rapidly that leading experts predict that the first bug-fixed quantum computers will be on the market by 2030.  

Developing bug fix methods is one of the biggest hurdles we face at present. Successfully building functional, fault-tolerant or bug-fixed quantum computers will lead to disruptive advances across a number of research fields and industries.  

Challenges

Quantum systems can lose their states – this is known as ‘decoherence’ in technical jargon. After certain periods of time, determining whether the quantum system states have changed becomes impossible, leaving measurements that might merely be the result of random noise, i.e. incorrect. Neither quantum systems nor their information outputs indicate whether quantum systems are, to put it bluntly, telling the truth or lying.  

Bugs creep in because, in physics, everything strives towards energy equilibrium. Quantum systems too strive for minimal energy differences from their environments. Perfectly isolated quantum systems that could maintain their states indefinitely would be impossible to control, because controllability and susceptibility to interference go hand-in-hand. The search for fault-tolerant quantum computers is attempting to find a way to deal with this difficulty – with one approach being to extend quantum systems’ state maintenance periods, and another to speed up operations to outpace decay.  

At the same time, researchers are seeking methods to distinguish between meaningful results and random noise, with the aim of measuring state decay and enabling continuous correction. Since quantum computers’ usefulness depends on their fault tolerance, the search for bug fix methods is one of the key fields of research in the further development of quantum computers.  

Focus on industry

Quantum computers are fundamentally different from conventional computers with respect to operation, and sometimes even work less well in certain areas. Since quantum computers are only suitable for specific problems and even then are likely to be particularly powerful only for very specific sub-problems, these problems must first of all be identified. Quantum computers will complement rather than replace traditional supercomputers. Even if quantum computers become established on the market, supercomputers will still handle many of today’s problems. Supercomputers will do the groundwork and follow-up work for quantum computers, in addition to handling all the problem components where quantum computers offer no advantages.  

This is why there has been substantial R&D investment in recent years, dedicated to quantum computer/supercomputer interaction. Current practical experience has already shown that connecting both worlds leads to results that neither quantum computers nor supercomputers could achieve on their own. The integration of quantum computers and supercomputers also promises to make quantum computers useful earlier.  

At the same time, bridging the two worlds poses its own challenges, in terms of both hardware and software.  

The software challenges involve ensuring efficient execution of programs containing both traditional and quantum algorithmic components. This requires appropriate development environments, not to mention programs that assign the respective tasks to either conventional or quantum computers.  

There are currently various paradigms for building quantum computer hardware, while corresponding software engineering is lagging behind hardware development in many respects. The skills required to program quantum algorithms are not yet widespread at present. ETH Zurich has responded to this skills shortage by introducing a corresponding Master’s degree programme.  

Today, most industrial projects in quantum computing are driven by scientific interests and are demonstrative or exploratory in nature. Researchers are presently putting quantum computers into operation with the aim of enabling potential users to gain initial experience with this new form of computing.  

While the buzz surrounding quantum computing has died down somewhat in recent years, intensive research into its further development is still ongoing – at universities, in industry and often in public-private partnerships.  

International perspective

Activities in quantum computing very much thrive on networking between universities and industry, between different companies, and also on exchange between different countries.  

Numerous countries have declared their quantum computing activities to be key strategic priorities, intensifying international competition. Switzerland is largely excluded from European quantum technology research projects. Swiss research funding acknowledges the strategic importance of quantum computing and has created a new tool to promote academic and industrial research: the Swiss Quantum Initiative (SQI). The aim of this endeavour is to compensate for some of the disadvantages arising from the impediments to cooperation with Europe, although it remains to be seen whether this initiative will be able to achieve is goal. 

Future applications

Global efforts to further develop quantum computing have led to major advances in recent years. Although it is still unclear when commercially available quantum computers will be operational, it is already becoming apparent that research and development efforts in this field are gaining momentum.  

It is expected that significant advances will be made in quantum computer/supercomputer interactions in the coming years, and that the first applications will be accessible through cloud platforms and will transcend purely scientific interests.  

Many companies are making significant progress in building quantum computers that will be made available to their customers and users alike. Some manufacturers are anticipating that fault-tolerant quantum computers will be available by 2030.