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Twelve things you need to know about quantum computing

Posted 4 Apr 2022

Quantum computing — understanding the basics

This blog answers some common questions on quantum computing, including the likely future impact, how a quantum computer works, how long we need to wait to see benefits, how the UK is positioned to take advantage of the new technology and mitigations needed for potential negative consequences.

1. Why do we need quantum computing?

Despite the massive increase in computing power which defines our modern world, there are still some tasks classical computers can’t handle well. For example, developing a room temperature superconductor would help solve the world’s energy problems yet research is blocked, in part, because classical computers can’t simulate quantum systems with many entangled particles. Medical research also suffers because classical computers can’t simulate large molecules and protein folding accurately. Optimisation and machine learning algorithms are sometimes limited by computing resource constraints. Quantum computers will — it’s believed — solve some of these difficult problems in the future, due to their fundamentally different computing paradigm.

2. How will quantum computing affect my industry?

Today’s Noisy Intermediate Scale Quantum (NISQ) devices have tens of qubits, and these qubits are very error prone. In the current NISQ era, Variational Quantum Algorithms (VQA), where a quantum computer is “trained” by a classical computer, are likely to be used for a wide range of things including quantum chemistry, fluid dynamics, machine learning and optimisation.

The “holy grail” of modern research is to build a large, universal, error corrected quantum computer, which could in principle run any quantum algorithm; with many positive societal impacts including revolutionising the challenge of climate change by discovering new materials for solar cells, batteries and even room temperature superconductors.

3. Which industries will benefit the most in the short term?

Multiple industries with complex supply chains will benefit from the ability to carry out better optimisations than are possible classically, and these are likely to be the first commercial use cases, with quick and significant paybacks.

Soon after, the pharmaceutical, chemical and material discovery industries will benefit from quantum chemistry. For example, quantum computers are being used to develop next-generation batteries. The aerospace and life science industries will also benefit from digital twins enabled by quantum fluid dynamics simulations.

4. How does quantum translate into economic opportunity?

Many businesses will benefit from improved quantum chemistry, fluid dynamics, machine learning and optimisation. These businesses will need to purchase not just a quantum computer, or cloud access to a quantum computer, but “the complete product”. They may need to purchase consultancy, to understand which problems are amenable to quantum computing, quantum software and the rights to use quantum algorithms. The quantum computer manufacturer will themselves need to source essential supply chain components such as dilution refrigerators, lasers, semiconductor nanostructure design and manufacture and microwave generators. All of these transactions provide an economic opportunity and begin to build a marketplace for a quantum industry.

5. What is a quantum computer?

Quantum computers depend on quantum effects that are only relevant at small scales, and we don’t see in our day to day lives. For example, a normal egg-timer starts off full, and then gradually empties as the sand drains out. The quantum equivalent, at the atomic scale, is completely different. A radiation pulse will cause an atom to transition between excited and ground quantum states, like the egg timer. Because in quantum mechanics energy comes in lumps, or “quanta”, after a pulse of appropriate length the atom is found with equal probability in the excited state or in the ground state. The pulse has placed the atom in a “quantum superposition” where it is in both the excited and ground states at the same time. The atom can be considered to be a “qubit”: the quantum equivalent of the classical computing bit.

6. How is quantum computing different from normal computing?

A bit used on normal, or “classical” computing, is only ever in one of two binary states, 0 or 1. Because of superposition, a qubit holds much more information. In a quantum computer, parallel processing over many qubits in superposition can give huge benefits over classical computers for some computations problems.

7. What is quantum supremacy and why does it matter?

Google claimed quantum supremacy when a superconducting quantum device with 53 qubits carried out a computation that could not be performed on a classical computer. The use of the word supremacy is now generally considered inappropriate because of its political connotations. The computation had no business value and the error rates were high: nonetheless, this important demonstration hinted at future quantum business advantage, where it will be cheaper or more convenient to use quantum computations for some applications.

8. How far aware are we from quantum computers being commercially viable — or actually being able to make an impact?

Most experts believe that quantum computers are three to eight years away from being commercially viable for some applications. Some would say that quantum computers are already making an impact. We are aware of one large company that has not fully operationalised a quantum optimisation programme, yet finds it helpful to run the algorithm daily to gain valuable insights into the best way to configure equipment routings through the maintenance organisation.

9. Who will quantum computing capabilities be available to in the near future?

Anyone can access a quantum computer at present. For example, using Qiskit it is possible to program a quantum circuit with a few lines of python code and submit this on a small IBM device. Large cloud computing vendors, such as Amazon Braket and Microsoft Azure enable cloud access to quantum hardware vendors, and manufacturers like D-Wave, and others, sell access to their devices.

10. How is the UK positioned to compete in the quantum computer industry?

The UK made an early start in funding UK quantum research, with total investment through the UK National Quantum Technologies Programme exceeding £1 billion since its inception in 2014. The National Quantum Computing Center (NQCC) annual report reports that the UK is joint fourth in quantum programme delivery and second in quantum technology commercialisation.

Although the global quantum computing industry is dominated by large, extremely well funded, American companies, there are several significant UK quantum computing companies. To name a few, Orca, based in West London, have built a photonic computer, and Oxford Quantum Circuits have built an eight qubit superconducting computer which is available on Amazon Braket. Phasecraft, Riverlane, Kuano and Feynman Solutions specialise in quantum software and quantum algorithms. Oxford Ionics, SeeQC, Universal Quantum, Quantum Motion and Duality carry out important fundamental research. Quantinuum is a recent merger of Cambridge Quantum’s advanced software development with Honeywell’s hardware.

The UK government has committed to build a large, universal, error correcting computer by 2040. This is likely to be sited at a well protected site in Harwell, Oxfordshire. Meanwhile the UK’s Centre for Doctoral Training (CDT) schemes are producing high-quality doctorates with the skills to design, build and develop quantum software and algorithms for future quantum computers.

11. Are there potential negative consequences of quantum like those we see with AI?

Shor’s 1994 quantum factorization algorithm shocked the research community by suggesting an impressive “quantum speed-up” that could undermine RSA encryption. Although the large, universal, fault tolerant devices needed to run the full algorithm are probably decades away, there are hints that a variation on this algorithm might break RSA encryption much sooner. The combined development and lifespan of Internet of Things devices (IoT) devices like modern cars can be very long and if an RSA encryption algorithm is hardwired in the chip there is risk that devices could still be in the field when quantum computers arrive that can break the encryption.

12. How do we prevent/ mitigate the possible negative consequences?

Any industry that depends on RSA or similar schemes to protect business secrets should be aware of the risk of “store now, break later” attacks. There is a strong case for implementing so-called “unconditional” or “everlasting” quantum-proof encryption algorithms, and reviewing encryption schemes for IoT devices.


Like any new technology it will take decades for the full impact of quantum computing to be seen. In the long term quantum computing will profoundly shape our future with impacts as dramatic as the invention of flight, or the silicon chip. It is very likely that in the next decade we will start to see quantum computers carry out computations simply not feasible on classical computers. The UK is well positioned to take advantage of this new technology because of its early strategic investment.


Daniel Goldsmith

Quantum Computing Technologist