From Classical Computers to Quantum Computers: The Revolutionary Technology Explained", "
Google has created a revolutionary new quantum computer called Willow that can perform a specific calculation in just five minutes – a calculation that would take the world's fastest supercomputers ten septillion years to complete, which is seventy times longer than the age of the universe itself. But how is this even possible? In this comprehensive exploration, we'll journey through the fascinating world of quantum computing, understanding the fundamental principles that make these incredible machines work and discovering why they represent humanity's next great technological leap.
The Birth of Quantum Computing: Richard Feynman's Revolutionary Vision
The story of quantum computing begins in 1981 at the Massachusetts Institute of Technology during a lecture titled "Simulating Physics with Computers." A brilliant scientist named Richard Feynman presented a groundbreaking observation that would change the course of computing history forever.
Feynman observed that quantum systems – including atoms, molecules, and subatomic particles – operate according to the principles of quantum mechanics. These quantum behaviors are so incredibly complicated that they cannot be understood or simulated using the straightforward binary logic of ones and zeros that classical computers employ.
His reasoning was profound and elegant: to understand nature at its most fundamental level, we would need a computer that itself operates on quantum principles. Feynman's famous statement became a rallying cry for future researchers:
"Nature isn't classical, dammit, and if you want to simulate nature, you'd better make it quantum mechanical."
In fact, Feynman proposed several beautiful ideas that would eventually become the backbone of quantum computing. He suggested that just as we use transistors as on-off switches in classical computing – where on represents one and off represents zero – we could use the spin of electrons in quantum computers. Spin up would represent one, and spin down would represent zero.
The Foundation Beyond Simple Spin States
However, simply assigning up or down spin values to electrons wouldn't automatically make a computer more powerful. The truly unimaginable power of quantum computers comes from two extremely powerful principles of quantum mechanics: quantum superposition and quantum entanglement. These principles fundamentally change what's possible in computation.
Understanding how these powerful principles are used in modern quantum computers requires us to first comprehend one of the most important experiments in quantum mechanics history: the double slit experiment. Pay close attention, because many people believe they understand this experiment when they actually don't, and without truly understanding it, you cannot properly comprehend quantum computers.
The Double Slit Experiment: Unlocking Quantum Mysteries
Imagine a straight plate with two parallel slits cut into it. If you fire grains of sand at this plate from the front, what pattern would you expect to see on a screen placed behind the plate? Common sense tells us we'd see two parallel lines – and that's exactly correct for sand particles.
But here's where common sense completely breaks down. If instead of sand, you fire subatomic particles like electrons or photons at the same double-slit plate, you won't see two parallel lines on the other side. Instead, you'll see what's called an interference pattern – multiple alternating bright and dark bands across the screen.
This interference pattern is something that waves create, not particles. Unlike particles, waves have a behavior where they interact with themselves – they interfere with each other. So does this mean that subatomic particles are actually waves, not particles? We were taught they were particles, weren't we?
Wave-Particle Duality: The Quantum Double Nature
The answer is both fascinating and counterintuitive: these entities are indeed particles, but they behave like waves. Their movement through our world occurs in a wave-like manner. This is why we speak of wave-particle duality – these particles exhibit a dual nature that defies our everyday experience.
When particles are fired at the two slits, something remarkable happens. The particle, behaving like a wave, passes through both slits simultaneously. Even though the particle is quantitatively one entity, it manages to pass through two different slits at the same time. This property of particles existing in multiple states simultaneously is called superposition.
This concept is difficult for our common sense to digest, but stay with me – it will start making more sense as we continue. Now imagine if we could somehow use this superposition principle to perform multiple combinations of calculations or computations simultaneously. This revolutionary idea first came to David Deutsch, often called the father of quantum computing, in the 1980s, and he began working on this concept.
Understanding Interference Patterns
Let's return to our experiment. When a wave passes through two slits, it breaks down into multiple waves that interact with each other, creating interference. There are two types of interference that are crucial to understand.
Constructive interference occurs when two waves of the same size and structure combine together. In this case, because they're combining, the resulting wave's size increases – they amplify each other. Destructive interference occurs when two waves cancel each other out due to being out of phase. In this case, the waves either become smaller or completely eliminate each other.
Looking back at the screen with the interference pattern, the bright stripes you see are the areas where constructive interference occurred – where waves converged and amplified each other. This is why more particles accumulated in those areas, creating the bright bands.
Probability: The Language of Quantum Mechanics
Let's pause for a moment and consider what we've learned from this experiment. First, you cannot pinpoint exactly where a particle will be found. However, you can estimate where the chances of finding it are highest. Second, you can also predict where the chances of not finding the particle are high.
All of this is due to the wave behavior of particles. Wave behavior is not deterministic but probabilistic. This means you cannot say with 100% certainty where a particle will be found. However, using probability mathematics, you can make your best guess about where particles might be found.
The bright areas on the screen represent highly probable areas where any fired particle might be found. The brighter and larger the area, the higher the probability of finding a particle there.
The Born Rule and Mathematical Certainty
Once we understood that the quantum world is based on probabilities rather than fixed outcomes, the quantum realm started making more sense to us. We began creating our own rules to understand it. In 1926, German physicist Max Born created his own formula that could predict the probability of a particle being found at any given location.
In essence, we started making uncertainty certain. These observations played the biggest role in the creation of quantum computers and quantum algorithms. The double slit experiment showed that particles could travel multiple paths simultaneously and ultimately reveal where their chances of being found are highest.
Can't this principle be used in a computer? Consider a problem where there are billions of options but only one correct answer, or just a few correct answers – like breaking the encryption code of high-security data.
The Fundamental Principle Behind Quantum Computing
In principle, if we break this down, building a quantum computer basically requires us to properly use quantum mechanics' probability principle and interference effects. By doing this, we can repeatedly combine many similar waves and their probabilities during calculations, getting closer to our answer with each processing step.
Just as we saw in the double slit experiment how waves interacted in a very particular way to show where a particle might land, we can make waves interfere in quantum computers. The computer suppresses all destructive or average wave patterns and focuses on those particular constructive interference patterns, causing the correct answer to amplify and emerge automatically.
Essentially, through quantum processing, we can literally build the correct answer from the interference of billions of waves. We just need some special algorithms to mathematically direct this process.
The Music of Quantum Computation
This is the fundamental principle behind quantum computers: eliminating all destructive interference and regular waves, removing noise, and letting waves that combine constructively interfere together – like coherent waves in music matching beat for beat. The correct answer will most certainly be found where the waves are most in harmony.
Let's understand this principle through an example, first using some common sense and then the correct interpretation of quantum mechanics.
Classical Bits vs Quantum Bits: A Fundamental Difference
In a normal classical computer, classical bits are used to transfer digital information. These are basically silicon transistors, as we learned in the previous video. The switching on or off of these transistors transmits information forward as zeros or ones. All the programs, words, and images you see on your computer screen are made from these codes filled with ones and zeros.
The most important characteristic of classical bits is that at any given time, they denote either one or zero – never both simultaneously.
The Power of Qubits
Quantum computers use a very special type of bit called qubits to transfer information. Whether a qubit is one or zero is decided by its particle spin – up spin means one, and down spin means zero.
Because qubits have the special property of superposition, they can display both states equally at the same time. For example, if you toss a coin, until it lands, the coin doesn't reveal its state and can be mathematically written as an average of both heads and tails.
Similarly, in the case of a qubit, until it's measured, it can exist in both states at the same time – binary one and zero simultaneously. Let me show you the real power of even a single qubit.
The Rat Maze Analogy
Imagine a complicated problem like a rat maze with 100 possible paths forward, but only one path leads out. In a traditional computer, to solve such a problem, the computer would have to go to the end of each path to find out which one actually leads out – a time-consuming sequential process.
But with qubits, remember they can exist in both states – state one and zero – at the same time, while a classical bit can only exist in one state. Therefore, a single qubit can travel two paths simultaneously and determine in the same amount of time where both paths lead. This is called parallelism in quantum computing language.
Exponential Power: The True Magic of Qubits
But here's where the magic truly begins. If we increase the number of qubits just a little, you'll start to understand their real power because processing power increases not linearly but exponentially.
With two qubits, they can exist in 2 to the power of 2, which equals 4 states simultaneously: the combination 1-1, the combination 1-0, the combination 0-1, and the combination 0-0. This means they can travel four paths in the maze at the same time.
With 3 qubits, they can travel 2 to the power of 3, which equals 8 paths simultaneously. And if we keep increasing, creating a simple quantum processor with just 100 qubits, do you know how many paths it could process at once?
Numbers Beyond Imagination
Just imagine: 2 to the power of 100 equals approximately 1.26 nonillion – that's a one followed by 30 zeros. This number is larger than the total number of atoms in the entire observable universe! And our maze only had 100 possible paths. Even if there were a billion possible paths, this processor would solve it in the blink of an eye.
This is exactly why Google's new processor could do in just 5 minutes what today's supercomputers would need 10 septillion years to accomplish. But it doesn't stop there.
Quantum Entanglement: The Magical Connection
Before I discuss the principle of quantum entanglement in quantum computers, let me clarify that the maze example we used was a simplified version to aid understanding. What actually happens is that the qubits together transmit billions upon billions of waves in every direction, and the quantum computer tracks their interferences.
Finally, the computer separates the destructive interferences and decodes the constructive interferences to find the correct answer. The place where most waves coherently match beat for beat is the correct answer because in the world of quantum physics, the universe always prefers the shortest path to any destination.
Feynman's Path Integrals
Richard Feynman also noticed this observation – that while there could be billions of paths from point A to point B, a particle has a unique tendency to probabilistically most certainly always travel the shortest path. Feynman mathematically proved this and developed Feynman's path integrals.
This is such a fundamental principle that it's the one principle that governs our entire universe. No theory has been able to contradict it yet – not even relativity or quantum mechanics.
The Spinning Top Analogy
Quantum entanglement is a phenomenon where two or more qubits become linked – entangled – as if they're magically connected and begin sharing information with each other, no matter how great the distance or difference between them.
Think of it like this: if a spinning top is rotating left to right and it becomes entangled with another spinning top, both tops will start spinning together in the same way, left to right, as if linked by a magical thread.
This only happens with quantum particles, but with these quantum particles, it doesn't matter if one particle is on Earth and the other is at the edge of the universe – they will remain connected. Plus, communication between them is almost instantaneous, making it potentially very useful for signaling between systems.
However, it's important to note that you cannot transfer classical information this way due to the limits of special relativity. Using this principle, many qubits can work together as a team, enabling calculations to be performed parallelly and extremely fast.
Common Misconceptions About Quantum Computers
Now that we understand the fundamental principles of quantum computers, everything seems fine, right? We've seen how powerful these computers can be. So what's next – just install them in every home so we can do regular work extremely fast? Playing games with realistic graphics would be so much fun, wouldn't it?
Let me bust two very important misconceptions about quantum computers.
Misconception 1: General Purpose Computing
First, quantum computers, as you've seen, are made to solve a different kind of problem altogether. They're not made to run Word, Excel, or PUBG like your PC. They're designed for problems where a lock might have billions of possible keys, but we need to find the right one fast. Or where we need to find factorials of large 200-digit numbers quickly.
Basically, they're for situations where we need to find interesting patterns from extreme amounts of data, or where we need to simulate quantum worlds, atoms, and molecules to understand their properties – problems that require extreme parallelism. These problems usually aren't faced by common people like you and me.
Quantum algorithms haven't yet become advanced enough to perform all general activities like a computer's operating system. Today, a quantum algorithm is built to solve very specific, limited types of problems, and we're gradually increasing the number of these algorithms and machines.
Misconception 2: Home Installation
Second, we'll only be able to install quantum computers at home when we learn to perform quantum processes at room temperature like nature does. It's a fact that even today, we don't know how nature, in plants, takes in light and carbon dioxide and converts them to sugar at room temperature.
Photosynthesis is a quantum phenomenon that we still don't know exactly how it happens at room temperatures. We can only perform quantum interactions at extremely low temperatures – close to minus 273 degrees Celsius, near absolute zero.
The Reality of Quantum Hardware: Giant Refrigerators
Look at what a quantum computer actually looks like. It's less of a quantum computer and more of a refrigerator – called an inner dilution refrigerator. The actual quantum chip is tiny, located at the base of this refrigerator.
The large, thick pipes you see pump helium or nitrogen down to the lower floors. The curled wires pass signals through microwaves and finally relay them to a classical computer. When this computer is turned on, it's placed inside a large cylinder-like enclosure called an outer dilution refrigerator to protect the processor from the external environment, heat, and electromagnetic radiation.
The Enemy: Quantum Decoherence
The biggest enemy of quantum processors is quantum decoherence – external interference in their waves. Here's the concept: quantum particles behave like waves, but as soon as they interact with another particle or energy, their wave form collapses, and they transform from a wave of possibilities into a single particle.
This means they lose their quantum properties like superposition and quantum entanglement, becoming useless for our purposes. The same happens with qubits – as soon as they encounter any kind of interaction, they immediately lose their quantum
