Quantum computers: an explainer

In the ever-evolving landscape of technology, quantum computers are emerging as the next frontier of computation. Some believe that quantum computers could even redefine the limits of human understanding and tackle problems previously deemed insurmountable.  

So what, exactly, are quantum computers? The answer sounds straightforward enough – they are computers that use the principles of quantum mechanics or quantum physics to perform computations. So instead of standard or supercomputers, which use classical bits (binary units of 0s and 1s) to process information, quantum computers use qubits (quantum bits) as their fundamental units.

But it would be an understatement to say that these are complicated machines – and as of yet, only a handful of prototype models exist.

How does a quantum computer work?

When exploring the field of quantum computers, it’s helpful to understand some of the principles that underpin the technology and help explain how the computers work. These include:

• Superposition. In the quantum world, particles like electrons or photons can exist in multiple states simultaneously. This property is known as superposition. Quantum bits (qubits) can also exist in a superposition of 0 and 1, which enables quantum computers to explore many possible solutions simultaneously, vastly increasing their computational power.
• Quantum entanglement. Entanglement is another phenomenon that quantum computers aim to leverage. When two particles become entangled, the state of one particle instantly influences the state of the other, regardless of the distance separating them. This property allows for highly efficient information transfer and processing.

In essence, quantum computers harness the principles of quantum mechanics – such as superposition and entanglement – to process information and solve problems far faster than a traditional computer ever could. 

Uses for quantum computers

Because quantum computers are able to perform complex calculations or solve problems currently beyond the capabilities of classical computers, it’s predicted that they will be able to aid in everything from cryptography and cyber security to artificial intelligence and machine learning – and beyond.

For example, a recent Harvard Business Review article, Quantum Computing Is Coming. What Can It Do?, states that quantum technology could significantly aid chemical and biological engineering thanks to the emerging feasibility of quantum simulations to help predict the properties of new molecules and molecule configurations:

“This ability means that quantum computers will play an important role in accelerating current efforts in materials discovery and drug development,” the article explains.

The benefits of quantum computers

Quantum computers offer several advantages over conventional computers. One commonly mentioned benefit is the exponential speed-up of computing power – tasks that would take classical supercomputers thousands of years could be completed in mere minutes with quantum computers, and even very large numbers or complex data would be easy for quantum computers to calculate.

But in more meaningful terms, quantum computers could help solve some of the biggest challenges facing the world today. For example, the World Economic Forum (WEF) has suggested that quantum computing could be one of the most innovation solutions to the climate crisis:

“Imagine being able to cheaply and easily ‘suck’ carbon directly out of our atmosphere. Such a capability would be hugely powerful in the fight against climate change and advance us towards the ambitious global climate goals set,” WEF stated in 2019. “Surely that’s science fiction? Well, maybe not. Quantum computing may be just the tool we need to design such a clean, safe and easy-to-deploy innovation.”

With the simulation possibilities that quantum computing could provide, even the most creative and complex solutions could easily be tried and tested – and then deployed in reality to help fight everything from climate change to food scarcity.

How many quantum computers are there in the world?

Tech giants and startups alike have been working to develop and scale quantum computing in recent years, and IBM, Microsoft, Amazon, and Google are among the frontrunners in developing quantum hardware and software.

While the exact number of quantum computers fluctuates, IBM is arguably the leader in quantum computing and has more than 20 quantum systems. 

“Late last year, IBM took the record for the largest quantum computing system with a processor that contained 433 quantum bits, or qubits, the fundamental building blocks of quantum information processing,” MIT Technology Review reported in May 2023. “Now, the company has set its sights on a much bigger target: a 100,000-qubit machine that it aims to build within 10 years.”

Challenges in quantum computing

While the potential of quantum computing is immense, it also faces several critical challenges:

• Decoherence. Quantum states are fragile and easily disrupted by external factors like temperature fluctuations or electromagnetic fields. Maintaining the delicate quantum state – or coherence – remains a significant challenge for quantum physicists and computer scientists.
• Error rates. Quantum computers have significantly higher error rates than classical computers due to the fragile nature of qubits. However, it’s worth noting that error correction techniques are actively being researched to mitigate this issue.
• Scalability. Building large-scale, fault-tolerant quantum processors is an ongoing challenge. Quantum computers need to scale for complex problems or computations, but at this time, the maximum number of possible qubits is less than 500. 

The future of quantum computing

The future of quantum computers is developing right now. Emerging areas and ideas in quantum computing include:

• Quantum algorithms. Researchers are continuously developing quantum algorithms that can harness the computational power of quantum computers. Among the most famous quantum algorithms are Shor’s algorithm and Grover’s algorithm.
• Quantum supremacy. The term quantum supremacy (or quantum advantage) refers to the point at which quantum computers outperform the most advanced classical supercomputers in specific tasks. 
• Quantum computing hardware. The development of quantum computing hardware is progressing rapidly. Different qubit technologies, such as superconducting qubits or trapped ions, are competing to become the leading choice for building scalable and fault-tolerant quantum processors.
• Quantum cryptography. Quantum cryptography is encryption based on the principles of quantum mechanics and is expected to revolutionise secure communication, offering a level of security that is theoretically unbreakable.

Learn the science that underpins quantum computing 

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