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Massive technologists like Google, Microsoft, IBM are trying to get the most out of quantum science. John Preskill has introduced the term *quantum supremacy,** which states the comparison between quantum and classical computing advantages in terms of speed and performance. And* it’s also the need for us to get into this as soon as possible. So let’s dig in without any further intro.

We would try to understand some fundaments of quantum computing in no time. I have tried making concepts clearer, rather than keeping them more complex. Please do hit claps only if you find it helpful. And for any advice to me towards improvement in the following article, please leave a comment in the comment section.

## Qubit

Qubit or a quantum bit is a rudimentary unit of information in quantum computers, i.e. the fundamental building block of quantum computing. It’s somewhat similar to the bit used in our classical computer, which we use in our day-to-day life. It has two states ∣0⟩ and ∣1⟩ when measured. Just consider a ball having two poles. The classical bit can be at the poles of the ball, but the Qubit can be anywhere on the ball so they can gain much information as compared to the bits. We can represent the Qubit as an electron, photon, or any subatomic particle.

## Superposition

Circumstances, where a system is in multiple states, are called superposition. The best example of superposition can be: suppose we flipped a coin, when it concludes the state while it falls on the plain, the states can be either x or y. but being in the air for time t, for that span, it simultaneously changes its state, like from x to y, y to x, and the flipping continues until it doesn’t get stable. So during flipping, it has multiple states, the condition of the coin before being stable is called a superposition.

## Quantum state

A quantum state is a state in which a physical system can exist. Like the above instance we clutched up, where we say the coin has two states x and y, so this x and y are called the states of that coin. A wave function describes the states.

## Entanglement

Entanglement occurs when the quantum state of each particle cannot be described independently of the quantum state of the other particle. A pair or group of particles interact with each other and share their fundamental properties. In which each of both particles in the pair can represent the properties of the other one. If one of them is measured it can inform about the other one. Entanglement is one of the phenomena that differentiates quantum computing from classical computing in terms of its powerful performance.

## Interference

We know that all objects have wavelike properties. Suppose we split these waves into multiples, then further these waves can interfere logically to form a single wave that is the superposition of the waves we split. Interference can be used to control the quantum states, which enables us to amplify the correctness leading to perfection in the result, by just shortening the incorrect features which cause a threat to the resulting correct answer.

## Quantum circuit

We can call a quantum circuit an arrangement of quantum gates, interconnect by quantum wires which involves operations on Qubits. These circuits are somewhat similar to the electronic circuits However the quantum circuits quantum gates are used and electronic circuits are made with electronic components.

## Quantum algorithms

An algorithm refers to the sequence of instructions, which are executed one by one specifically to solve a problem. In the same way, a quantum algorithm is a step-by-step procedure to solve a problem, like a classification problem. Both the type of algorithms only differ in their basic unit of information.

## Quantum coherence & decoherence

In quantum computing, we describe the subatomic particles in form of waves, i.e. quantum states of the system are represented as waves in mathematical terms. The logical relationship between multiple waves is called coherence. The coherence should exist to perform quantum computing. As a result, the waves should pose coherent nature.

**Decoherence **is when there is no existence of coherence. For the retention of coherence, the quantum systems are put into colder environments and isolated properly to avoid the loss of coherence due to external effects like noise. Quantum computers are extremely sensitive. If not isolated properly, they can lack information and will make improper computations.

## Quantum mechanics

Quantum mechanics, a physical science that deals with the behavior of physical properties of nature on atomic and subatomic level i.e. on particles like photons, electron, molecules, etc. to

## Quantum gates

Quantum gates are the basic building blocks of a quantum circuit that perform operations on qubits. quantum gates are reversible and are unitary operators. Reversible **(reduces the wastage of heat. The reversible gates have a one-to-one mapping between the input and output vectors, this helps in constructing the input vector from the output vector)**. The classical operation can also be performed on the quantum gates.

## Quantum complexity

The computational complexity focuses on categorizing computational problems as per their resource usage. However, quantum complexity is the subfield of computational complexity that deals with complexity classes that are defined using quantum computers. The complexity class is just a collection of problems, majorly the time and energy problems are commonly analyzed. In simple terms, it monitors the complexity of the problems, that is what is the difficulty level of the problem, and also compares it to the classical problem.

## Quantum amplitudes

The height of the wave in the figure is the amplitude.

Quantum amplitudes are nothing but probability amplitudes, they define the relationship between the quantum states of the system. It is the wave function, which is the quantity associated with the moving particles. It has a complex nature. It shows us the behavior of the particle. It is denoted by Ψ.

## Quantum annealing

Quantum annealing is a quantum computing method that is used to find the best solution for a problem having multiple solutions using quantum properties like tunneling, superposition, entanglement, etc.

Quantum annealing also includes adiabatic computation, it is the class that includes all the procedures to solve optimization problems using quantum computing.

Hope you’ve had a good moment and learned a lot of new things or might be you aware of it. Please hit claps if you feel it interesting. It will push me to make more like this.

## References

A whole bunch of thanks to the people behind these references.

https://en.wikipedia.org/wiki/Quantum_computing

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