Unveiling the Stack: Classical Stack Vs. Quantum Stack
Tags: quantum, quantumcomputing, computerscience
Published: 2023-11-21 06:31:40

**What is Stack**?
In the realm of computers, they are like a city itself going through various constructions. That’s why a structured organisation is imperative to understand the operations going through it. This layered structure in classical computers is known as stack that is built up like stacks ranging from the primary classical bits to the user-facing applications. The stack organises all layers of computer’s operations, starting with the most fundamental and hidden from the side on the bottom. We will work our way from classical bits to the applications today.

**Classical Bits**: Bits are the fundamental unit of information in a computer. Each bit of information can be either a 0 or 1. Every app, website, image, text, program, and more is built from bits. It serves a building block for every facet of digital existence. There are various complex systems like Trits or digits but the binary system prevails  because of the simplicity. The simplicity is important when packing billions of bits into devices like laptops.

**Classical Gates**: Gates can manipulate bits. They allow us to turn inputs into outputs. Whether a light is turned on or off, classical gates work as an architect of binary manipulation. These gates work like real magic performing logical operations like AND, OR and NOT operation and transform inputs into desirable outputs which further pave the way for more advanced operations.

**Classical Circuits**: A circuit is a sequence of gates. By combining many different gates in certain orders, we can start to process inputs into outputs in more complex and interesting ways. We can establish circuits by combining different gates in specific arrangements which can perform complex computations from simple to advanced arithmetic algorithms. 

**Algorithms and protocols**: Algorithms & Protocols are the agreed-upon steps computers use to solve problems. This layer guides processes like search algorithms and streaming protocols. 

**Applications**: We interact everyday with applications and it appears top of the stack. Applications are how we use algorithms and protocols to solve problems which offer real life challenges and the perfect solution. Applications are user-friendly interfaces that transform complex computational processes into accessible functionalities.

**Limitations of Classical Stack**
When it was first proposed in the 1960s, Moore's Law predicted that computer power would double every two years. Decades of invention were sparked by this prediction, which pushed humanity into an era where computational capabilities were limitless. But when we go closer to the scale of atoms, Moore himself pointed out that there are some fundamental obstacles to overcome. After a certain size quantum effects begin to cause a problem.The main problem is quantum effects, like tunnelling which means An object that can teleport to the other side of a closed barrier without ever touching it, causes classical computers to work incorrectly, meaning we cannot continue making classical computers more powerful for much longer. This is the end of Moore's Law.

For example, Transistors are designed to stop thе flow of electricity when thеy arе in thе "OFF" statе. But even whеn thе transistor is turnеd "OFF," thеrе's a chancе that еlеctrons could tunnеl past obstacles and appеar on thе othеr sidе of thеm duе to thе quantum naturе of еlеctrons. This quantum mischievous behaviour obscurеs thе diffеrеncе bеtwееn 0s and 1s, causing еrrors in our computations and upеnding thе fundamеntal principlеs of convеntional computing. 

**Why Quantum Stack**?

As we approach the end of Moore’s Law, the quantum stack comes as a ray of hope. In contrast to classical stack, the quantum stack uses the principles of quantum mechanics to overcome the limitations.  The replacement of classical bits with quantum bits, or qubits, causes a paradigm change in information processing. The quantum stack looks similar to the classical stack, but uses quantum mechanics

**Quantum Bits**: A qubit is a quantum bit. It is the fundamental unit of quantum information and can be in the 0 or 1 state or a superposition which means in a combination of these two states. For example, A qubit in superposition is like a coin flipping in the air. We seemingly can't know what state it will be in until we force it to be in one or the other (measurement). But unlike the coin, there is nothing we could do to know what state it will be in beforehand Quantum mechanics is truly random.

**Quantum Gates**: Quantum gates perform some quantum operation on qubits to change their state in order to perform quantum computations. For example, in X gate, it gives the opposite input. If the initial qubit state is 0, then the resulting qubit state is 1 and if the initial state is 1 then the resulting qubit state is 0. On the other hand, H gates create equal superpositions. If the initial qubit state is 0, the resulting qubit state will be an equal superposition meaning it can be 0 and 1 at the same time.

**Quantum Circuits**: Quantum circuits are a sequence of quantum gates acting on qubit or group of qubits. We can extract information about an unknown quantum state through quantum measurement.

**Quantum Algorithms and protocols**: Algorithms and protocols are agreed upon steps computers used to solve problems. They are implemented with special purpose quantum circuits. 

**Applications**: Applications of quantum computers range from cybersecurity to stimulating other quantum mechanical systems. Discovery of new applications is an active area of research, particularly those that apply to climate change solutions, supply chains, finance prediction and medicine discovery.

Therefore, combined with all layers become an unifying architecture named Stack. It provides a comprehensive framework for the understanding of modern computers. From the classical bits to user-friendly applications, every layer plays an important role in the digital operations. Undеrstanding thе stack may hеlp anyonе, whether thеy are a tech passionate or just a kееn lеarnеr, undеrstand thе innеr workings of thе digital world and rеducе thе complеxity of computing.