Unless you have been living under a rock, you must have come across the news about “Willow”, Google’s latest breakthrough in quantum technology. What’s so shocking about Willow is the fact that it can solve a problem in just five minutes that would have taken a classical supercomputer ten septillion (10 followed by 25 zeroes!) years to solve. This mind-blowing fact caused me to go down a rabbit-hole of quantum computing and let me just state that quantum computing is every bit (or qubit) as cool as it sounds. This article will give you a beginner-friendly, yet thorough, introduction to quantum computing and all its applications and implications.

"Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical."
— Richard Feynman, Theoretical Physicist

What is Quantum?

Before delving into the concepts of quantum computing, let's actually explore the notion of “quantum” itself. If you, like me, are a Marvel fan, you probably associate quantum with cool stuff like parallel universes, multiverse and atom-related phenomena. Well, you’re not too far off, although unfortunately reality is not as magical as fiction. Nevertheless, quantum concepts are still very interesting and promising.

"Anyone who can contemplate quantum mechanics without getting dizzy hasn't understood it."
— Niels Bohr, Physicist.

The Origin of the “Quantum” Concept

The concept of “quantum” traces back to the early 1900s when scientists realized that classical physics couldn’t explain certain mysteries of the microscopic world. Max Planck proposed that energy isn’t continuous but comes in tiny packets called “quanta.” Einstein later expanded this idea, showing that light can behave as both a particle and a wave—a discovery that laid the foundation for quantum mechanics.

Classical physics works perfectly for things like planets and cars but fails at atomic scales. For instance, electrons don’t orbit the nucleus like tiny planets; instead, they exist as probabilistic clouds. Groundbreaking work by scientists like Niels Bohr, Werner Heisenberg, and Schrödinger introduced ideas like superposition and uncertainty, forever changing our understanding of reality.

Fig 1. Schrödinger's cat is both alive and dead until observed, illustrating quantum superposition

Quantum Mechanics: The Physics of the Very Small

Quantum mechanics is the physics of the incredibly small, where particles like electrons and photons defy our everyday logic. Unlike objects we’re familiar with, these particles can behave as both waves and particles (wave-particle duality) and exist only in discrete energy levels (quantization). Even stranger, their behavior is probabilistic, meaning we can only predict the likelihood of where or how they’ll behave, but not know for sure.

Experiments like the Double-Slit Experiment (a high-school physics concept that still gives me trauma) showed that particles can interfere with themselves, acting like waves until observed. Schrödinger’s famous “cat” thought experiment illustrated superposition - the idea that something can exist in multiple states simultaneously (find more about this intriguing concept here: What Is Schrödinger’s Cat?). These odd phenomena aren’t just mind-bending and cool theories; they form the backbone of quantum computing, giving rise to powerful techniques like superposition and entanglement, which we will explore later.

Fig 2. The double-slit experiment shows particles act as waves when unobserved

What is Quantum Computing?

Quantum computing uses the principles of quantum mechanics to process information in ways that classical computers cannot. Instead of relying on classical binary bits (0 or 1), it uses qubits, which can represent both 0 and 1 simultaneously through a property called superposition. Quantum phenomena like entanglement and interference enable quantum computers to solve certain problems exponentially faster than classical computers.

Fig 3. Google’s Willow chip

A Brief History

The history of quantum computing can be traced back to the 1980s when Richard Feynman and Yuri Manin independently proposed the concept. Feynman suggested that simulating quantum systems on classical computers would be incredibly difficult, and proposed that quantum systems themselves could be used for computation. This laid the foundation for the field of quantum computing, which aims to utilise the principles of quantum mechanics to perform calculations that are difficult for classical computers.

Qubits - the Foundation of Quantum Computing

Qubits are the essential components - basically the building blocks - of quantum computing. They enable parallelism which is the ability that quantum computers stand out for.

Bits vs. Qubits

Classical computers use bits to represent 0 or 1. In contrast, qubits can exist in a superposition of both 0 and 1 simultaneously, enabling parallel computations. This unique property allows quantum computers to explore multiple solutions at once, vastly improving efficiency for certain tasks.

Fig 4. Qubits can exist in a superposition of both 0 and 1 simultaneously

Types of Qubits

Qubits can be implemented in various ways, depending on the underlying technology:

Superconducting Qubits: Use superconducting materials cooled to near absolute zero for stability and speed. These are the most commonly used qubits in present-day quantum systems. Example: Google’s Willow and Sycamore chips.
Trapped Ions: Utilize ions suspended in magnetic fields; known for precision and long coherence times.
Photons: Make use of light particles for quantum communication and cryptography.
Quantum Dots: Capture single electrons in semiconductors for scalable quantum systems.
Neutral Atoms: Use lasers to manipulate neutral atoms. This technique allows for scalability and versatility.

Properties of Qubits

Qubits have four main properties which make quantum computing possible. And the only word to describe these properties is “cool” - each of these just shows how incredibly intricate and unique qubits are, and the limitless possibilities they embody.

Superposition: Unlocking Parallelism

Qubits in superposition can represent multiple states simultaneously. For instance, with 3 qubits, a quantum system can represent 8 states (2³) at once. Now imagine how many states 100 qubits can represent. And with like a million qubits - well the possibilities are (literally!) endless. This means that quantum computers can process information exponentially faster for complex problems.

Fig 5. A quantum system with 3 qubits can represent 8 states (2³) at once

Entanglement: Spooky Action at a Distance

When qubits are entangled, the state of one directly influences the other, even if separated by large distances. You can think of this as the qubits having very strong, unbreakable bonds that persist spanning large distances, and are affected by each other. This phenomenon, described by Einstein as “spooky action at a distance,” (yes, Einstein came up with this line, not me) enables quantum computers to perform computations with incredible efficiency and coordination. Coordination being the key point here, again supplementing the idea of parallelism.

Fig 6. Entanglement in qubits

Decoherence: The Achilles’ Heel of Quantum Systems

Despite their incredible, almost magic-like properties, quantum systems aren’t, unfortunately, completely impenetrable. They have their limitations; quantum systems are highly sensitive to their environment. Factors like heat, vibrations, or stray particles can cause decoherence, a condition where qubits lose their quantum state. This is why quantum computers operate at near-absolute-zero temperatures and require error correction - all to prevent decoherence which renders qubits useless for the current computation.

Fig 7. Decoherence is a condition where qubits lose their quantum state

Interference: Fine-Tuning Probabilities

To understand this concept, I’d like you to rewind back a bit back to high-school physics, particularly the topic of waves. You may be able to recall that when the periods of waves match and they are in sync with each other, the waves sort of join together and give rise to an amplified wave (constructive interference). In contrast, waves with differing periods, that are out of sync with one another, cancel each other out entirely (destructive interference). Quantum systems use this exact same concept, called interference, to amplify correct solutions and cancel out incorrect ones. By manipulating wave-like probabilities, quantum computers optimize their output during computations.

Fig 8. Interference in waves

Classical vs. Quantum Computing

Now that you (hopefully) have a solid understanding of quantum computing and how it works, let's go deeper into how it differs from and has an advantage over classical computing.

Quantum computers transcend the limitations of classical computing by operating beyond the confines of our familiar reality. They tap into the inherent parallelism of the quantum world, where possibilities exist not as individual choices but as a superposition of all possibilities, an amalgamation of all potential outcomes.

The Binary World of Classical Computing

Classical computers operate using bits, representing information as either 0 or 1. They excel at sequential (step-by-step) calculations and deterministic (fixed outcome) tasks but struggle with complex problems involving numerous variables, relying on brute-force (trying all possibilities one by one) methods. These limitations stem from the binary nature of computation and the physical constraints of transistors.

Transistors can basically be thought of as tiny switches that control the flow of electricity. With the passage of time, the size of these switches has continued to grow smaller and smaller, allowing more and more of them to be packed in a single chip. This miniaturization has been a key driver of the incredible progress we've seen in computing power.

An important concept in computing is Moore’s Law. Moore's Law states that the number of transistors on a computer chip doubles roughly every two years, leading to a significant increase in computing power over time. This Law has held true till now.

Fig 10. Moore’s Law

However, hindrance in further realisation of Moore’s Law is fast approaching. This is because, as transistors get smaller and reach atomic scales, quantum effects and heat generation become significant, hindering further miniaturization and the continued exponential growth of computing power predicted by Moore's Law. This limitation drives the exploration of alternative approaches like quantum computing which have the ability to tackle problems like factoring large numbers or simulating complex systems, which classical computers just cannot.

How Quantum Computing Redefines Problem-Solving

As discussed earlier, quantum computers operate using qubits, the fundamental units of quantum information. Unlike classical bits, which can only represent 0 or 1, qubits can exist in a superposition of both states simultaneously - kind of like a multiverse. This unique property, combined with other quantum phenomena like entanglement and interference which we’ve already explored, allows quantum computers to perform calculations in fundamentally different ways.

Instead of working sequentially, step-by-step like classical computers, quantum computers can explore multiple possibilities simultaneously, thanks to the principle of superposition. This parallel processing capability enables them to tackle complex, probabilistic problems that would take classical computers an exorbitant amount of time, potentially even millions or billions of years.

In essence, quantum computers transcend the limitations of classical computing by operating beyond the confines of our familiar reality. They tap into the inherent parallelism of the quantum world, where possibilities exist not as individual choices but as a superposition of all possibilities, an amalgamation of all potential outcomes.

The Travelling Salesman Problem

To actually demonstrate the differences between classical and quantum computing and give you a solid, visual sort of idea about their problem-solving approach, we’re going to explore the Travelling Salesman Problem (TSP), an age-old puzzle.

What is the Traveling Salesman Problem?

Imagine you’re a salesman tasked with visiting a list of cities, say 10, starting and ending at the same city. Your goal? To find the shortest route that lets you visit each city exactly once. Sounds simple, right? Well, it’s not. The number of possible routes increases exponentially as you add more cities. For 10 cities, there are over 3.6 million possible routes. For 20 cities, the number jumps to a staggering 60 quintillion! This is because the salesman can visit the cities in any order. For n cities, the total number of routes is given by (n-1)! (the starting and ending cities are fixed, leaving (n-1) cities to arrange in all possible orders).

This kind of problem falls into a category called NP-hard problems - problems that grow so complex, they are practically impossible for classical computers to solve efficiently as the number of variables increases.

How Classical Computers Handle It

A classical computer, relying on its trusty binary bits, approaches the TSP using brute force. Essentially, it evaluates each possible route one by one, calculates the total distance, and identifies the shortest one. For a small number of cities, this is manageable. But as the number of cities grows, the time required to compute all possibilities spirals out of control. Even the most powerful supercomputers on Earth would take millions of years to solve the TSP for a significant number of cities. Why? Because classical computers process information sequentially, considering one possibility at a time.

How Quantum Computing Redefines the TSP

Enter quantum computing. Quantum computers tackle the TSP not by evaluating each possibility one by one, but by leveraging superposition and quantum parallelism. Instead of brute-forcing the solution, they can encode all possible routes into the quantum states of qubits and evaluate them simultaneously. In other words, a quantum computer can explore all routes at the same time.

This is where quantum interference plays its part. Through specially designed quantum algorithms, paths that lead to longer routes interfere destructively and cancel out, while paths leading to the shortest route interfere constructively, amplifying their probabilities. The result? The quantum computer effectively “zeroes in” on the optimal route without sifting through each one individually.

The Role of Quantum Computing in Cybersecurity

The most interesting aspect I find about quantum computing is its major role in cybersecurity. In fact, you’ll barely be able to find any discussion on quantum computing without a segue into cybersecurity as well. This is because quantum computing has the potential to have a huge impact on cybersecurity, changing the field as we know it.

"The very fast computing power given by quantum computers has the potential to disrupt traditional businesses and challenge our cyber-security."
— Jungsang Kim, Professor of Electrical and Computer Engineering at Duke University.

Quantum computing holds the potential to revolutionize cybersecurity, both as a threat and as a tool for defense. Current encryption systems, such as RSA and ECC (Elliptic Curve Cryptography), rely on the computational difficulty of factoring large prime numbers or solving discrete logarithms—tasks that would take classical computers thousands of years to complete. This very property makes them so well-suited for encrypting data on the internet, like the Whatsapp messages you send, because it is infeasible to decrypt the data through brute force as it would take tens of thousands of years.

However, quantum computers equipped with algorithms like Shor’s Algorithm could crack these codes exponentially faster, rendering much of today’s encryption obsolete. This poses a serious risk to secure communications, financial systems, and even national security.

Nevertheless, all hope is not lost. When there is a problem, you can trust scientists and researchers to find a solution as well. To counteract this quantum threat, researchers are developing quantum-safe cryptographic methods, such as post-quantum cryptography, which are designed to withstand attacks from quantum computers. Another promising solution is Quantum Key Distribution (QKD), which utilises the principles of quantum mechanics, like entanglement and superposition, to create secure communication channels. QKD ensures that any interception of a quantum key alters its state, making it detectable and rendering the data useless to attackers - very similar to the concept of blockchain. Financial institutions, such as HSBC, and governments worldwide are already testing QKD for safeguarding sensitive communications.

Beyond the aforementioned defensive measures, quantum computing could also strengthen cybersecurity through advanced threat detection. Quantum-enhanced AI systems could analyze vast datasets to identify and neutralize cyber threats faster and more accurately than traditional methods. While the road to fully integrated quantum cybersecurity is still under construction, its dual role as both a challenge and a solution will undeniably shape the future of secure digital infrastructure.

One interesting, and perhaps somewhat scary, fact that I’d just like to drop here is that malicious users are actively, at this very moment, capturing and storing vast amounts of sensitive encrypted data. In its current form, the encrypted data is, of course, useless to these malicious users. However, once quantum computing is able to break the current state-of-the-art cybersecurity algorithms, the interceptors will be able to decrypt the stored data and potentially gain access to sensitive and highly confidential information belonging to financial institutions, governments, military etc.

Applications of Quantum Computing

Even though currently quantum computing is still in the research stage, its applications are numerous and ground-breaking. Once quantum computing is advanced enough to be applied practically, it could quite literally change lives and give rise to a new “quantum” age. Listed below are some of the most significant uses of quantum computing in real-world scenarios.

1. Advancements in Pharmaceuticals and Medicine

Simulating Molecular Behavior: Quantum computers excel at modeling molecular interactions at a quantum level, which classical computers cannot efficiently do. This enables the simulation of complex biochemical reactions that form the basis of drug discovery and development.
Drug Discovery: Quantum algorithms can identify and optimize potential drug compounds by exploring vast molecular combinations in a fraction of the time it would take traditional methods.
Protein Folding and Disease Modeling: Quantum systems can better model complex protein structures, aiding in understanding diseases like Alzheimer’s and Parkinson’s.
Faster R&D: The shift from physical experiments to quantum simulations can cut the drug development cycle from years to days.

2. Revolutionizing Chemistry and Materials Science

Catalyst Development: Quantum computers can optimize chemical reactions, paving the way for more efficient and environmentally friendly industrial processes, such as developing better catalysts for energy conversion or carbon capture.
Artificial Fertilizer Production: Quantum systems could replicate natural processes like nitrogen fixation at room temperature, making fertilizer production more sustainable and efficient.
New Materials: Quantum simulations can design novel materials for high-performance batteries, superconductors, and lightweight alloys.

3. Enhancing Machine Learning and Artificial Intelligence

Optimized Algorithms: Quantum computers can process exponentially more data points simultaneously, enabling the creation of highly efficient and accurate machine learning models.
Pattern Recognition: Improved algorithms for recognizing complex patterns in data (e.g., for image and speech recognition) could lead to advancements in AI systems.
Big Data Analysis: Quantum systems excel in analyzing massive datasets, which is critical for industries like finance, healthcare, and logistics.

4. Logistics, Optimization, and Supply Chain Management

Optimization Problems: Quantum computers can tackle NP-hard optimization challenges, such as the Traveling Salesman Problem, to optimize routes and reduce costs in logistics.
Supply Chain Efficiency: By modeling and simulating supply chains, quantum systems can predict disruptions and recommend the best adjustments in real time.
Energy Savings: Quantum systems could optimize transportation networks and warehouse operations, reducing fuel consumption and operational inefficiencies.

5. Climate Science and Energy Solutions

Energy Optimization: Quantum computers can optimize power grid operations, balancing supply and demand more effectively and reducing energy waste.
Fusion Energy: Quantum simulations can stabilize plasma within fusion reactors, potentially unlocking a sustainable and limitless energy source.
Carbon Capture: Quantum algorithms could help design efficient methods for capturing and converting CO₂ into useful products.

The Quantum Race

Considering the promise quantum computing holds, it is not a surprise that the major tech giants are all dipping their toes into and testing the waters when it comes to making advancements in the field of quantum technology. And at this point, there is definitely a competitive factor as not just tech companies, but entire countries themselves, are going neck to neck to be at the forefront of quantum revolution.

"Our quantum roadmap is a clear path to achieving quantum advantage, which we believe will lead to solving problems that are currently intractable."
— Dario Gil, Senior Vice President and Director of IBM Research.

Key Players: IBM, Google, Microsoft, and Emerging Startups

The race to dominate quantum computing is in full swing, with key players like IBM, Google, and Microsoft leading the charge. IBM’s Quantum System 2, designed with superconducting qubits, aims for scalability and long-term quantum utility by 2033. Google’s latest breakthrough, the Willow Chip, has set new performance benchmarks, improving coherence times and introducing advanced error correction. Microsoft is working on topological qubits, a novel approach promising higher error resistance. Meanwhile, startups such as Rigetti, IonQ, and D-Wave are carving their niches—pioneering hybrid classical-quantum systems and early-stage commercial applications.

"We aim to build a useful, error-corrected quantum computer that can solve real-world problems."
— Hartmut Neven, Director of Quantum Artificial Intelligence Lab at Google.

These companies aren’t just vying for quantum supremacy (the ability to outperform classical computers for specific tasks) but also for quantum utility—delivering practical, real-world benefits. This makes the race not just technological, but deeply commercial, with the quantum industry projected to reach $1.3 trillion by 2035. (So if you’re thinking of shifting gears and pivoting to quantum computing, well, I’m not gonna judge you).

The Role of Governments: US, China, and Beyond

National governments are heavily involved in the quantum race, recognizing its implications for both economic growth and national security. The US has invested billions in quantum research through initiatives like the National Quantum Initiative Act. And where there is USA, it’s inevitable that China doesn’t emerge as a rival; China, with over $15 billion in quantum investments and half the world’s quantum patents, has made significant advances, such as quantum satellites enabling secure communication over long distances. Europe and countries like Singapore are also stepping up, focusing on collaborative quantum communication networks and satellite-based quantum key distribution.

"Quantum computing holds the potential to drive innovations across the American economy, yet it also poses significant risks to the economic and national security of the United States." — National Quantum Strategy, United States.

Collaborative Efforts vs. Geopolitical Competition

While the quantum field thrives on collaboration, geopolitics plays an undeniable role. The US-China quantum race has elements of a technological arms race, with concerns about cybersecurity and espionage. Yet, global collaboration is evident in areas like the OpenQASM standard and the Qiskit community, which bring together researchers from around the world. This tension between cooperation and competition show how high the stakes are - quantum computing could redefine economic and geopolitical power.

Current Milestones: Quantum Volume, Error Correction, and Quantum Supremacy

Key milestones in the quantum race include achieving quantum supremacy (first claimed by Google in 2019) and advancements in error correction. IBM’s metrics like Quantum Volume and CLOPS (circuit layer operations per second) are redefining how we measure quantum performance, moving beyond just raw qubit counts. With error correction codes now 10 times more efficient than before, we are inching closer to practical quantum computing with billions of quantum gates.

The Road Ahead

Having covered so much ground when it comes to quantum computing, let's take a look at what the (near) future holds when it comes to this revolutionary field. Considering the pace of advancements in quantum computing, it is clear that the quantum revolution will take place sooner rather than later.

Predictions for Quantum Utility and Quantum Advantage

Quantum computing is poised to move beyond proof-of-concept demonstrations toward quantum utility, where systems provide tangible advantages in fields like drug discovery, supply chain optimization, and machine learning. Experts predict major breakthroughs in the next 5–7 years, with IBM targeting a quantum system capable of running 1 billion quantum gates by 2033 (that’s a little too close for comfort, honestly). Achieving quantum advantage—where quantum computers outperform classical methods for meaningful problems—remains the holy grail and could redefine industries.

The Future of Quantum-Classical Hybrid Systems

The immediate future lies in quantum-classical hybrid systems, where quantum processors work in tandem with classical supercomputers. These setups make use of the strengths of both: classical systems for general-purpose tasks and quantum systems for complex problems like molecular simulations or solving NP-hard problems. Cloud-based quantum computing platforms are already paving the way, making quantum resources accessible to researchers and businesses globally.

Societal and Ethical Considerations for a Quantum Future

As with any disruptive technology, quantum computing raises ethical questions. For instance, its potential to break widely-used encryption poses a cybersecurity risk, necessitating the rapid adoption of quantum-resistant cryptography. Beyond this, concerns around equitable access to quantum resources and their environmental footprint (due to massive cooling requirements) are gaining attention. With the already rising issues of climate change, this just adds fuel to the fire (pun not intended). The field must also address the risk of geopolitical misuse, such as using quantum advancements for surveillance or cyber warfare.

Fig 11. This is the hardware required for keeping the temperature sufficiently cool necessary for quantum computing

What Quantum Computing Means for Humanity

Quantum computing has the potential to transform humanity’s understanding of the universe, from simulating protein folding to modeling the Big Bang. It could help address some of the most pressing global challenges, from climate change to energy crises. However, its true impact will depend on how societies balance innovation with ethical stewardship. Whether quantum computing ushers in a utopian era of scientific breakthroughs or exacerbates inequalities remains to be seen. For now, one thing is certain—quantum computing is no longer science fiction; it’s the next revolution in human history.

The only thing to do now is to keep our fingers crossed that this revolution will be a good one, changing lives for the better. My advice for all the readers who’ve made it till here would be to keep updated with quantum computing and the latest developments in this field. Who knows, you might just be one of the contributors in the quantum revolution.

I would like to show my appreciation for and give credit to some excellent videos and articles I consumed in order to obtain enough knowledge on quantum computing to be able to write this article.

https://youtu.be/-UrdExQW0cs?si=4ISx2ivDQ_CR9_cL

https://youtu.be/e3fz3dqhN44?si=0-ZiTlwDyGRx-H0O

https://youtu.be/W7ppd_RY-UE?si=vsbyZ-RE0Y8H3O9P

https://youtu.be/1_gJp2uAjO0?si=zkJZhl8l5tvzE-Rn

https://youtu.be/qQviI1d_hFA?si=c5-J8cKjOaZ6yYkX

https://youtu.be/zhQItO6_WoI?si=cowa9JugeeqM-OXI

https://youtu.be/_OjRClPzU6Y?si=8BK-VOvND_iFUfWf

https://www.ibm.com/topics/quantum-computing