Quantum computing is a branch of computing that uses the principles of quantum mechanics to perform operations on data. Quantum mechanics is a branch of physics that deals with the behavior of particles on a very small scale, such as atoms and subatomic particles. In classical computing, data is represented using bits, which can only be in one of two states: 0 or 1. In quantum computing, data is represented using quantum bits or qubits, which can exist in multiple states simultaneously.

One of the key principles of quantum mechanics that is used in quantum computing is superposition. Superposition states that a qubit can exist in multiple states at the same time. For example, a qubit can be in the state of 0 and 1 at the same time. This is known as a superposition of states.

Another key principle is entanglement, which states that two or more qubits can become entangled, meaning that their states become linked together. When two qubits are entangled, the state of one qubit can instantly affect the state of the other qubit, even if they are separated by large distances. This is known as quantum entanglement.

One of the main advantages of quantum computing is that it can perform certain types of calculations much faster than classical computers. For example, quantum computers can quickly factor in large numbers, which is a critical step in many encryption algorithms. This makes quantum computers potentially useful for tasks such as breaking encryption codes or simulating complex chemical reactions.

However, quantum computing is still largely in the research and development stage. Building and controlling a quantum computer is extremely difficult and requires a deep understanding of quantum mechanics and advanced technology. Quantum computers are also highly sensitive to their environment, so they must be kept at very low temperatures and isolated from external interference.

In summary, quantum computing is a branch of computing that uses the principles of quantum mechanics to perform operations on data. It uses qubits that can exist in multiple states at the same time, which allows it to perform certain types of calculations much faster than classical computers. However, they are extremely difficult to build and control and are still largely in the research and development stage.

### Who discovered Quantum computing?

The concept of a quantum computer was first proposed by physicist Paul Benioff in 1980. However, the field of quantum computing has been developed by many scientists and researchers over the years, with contributions from a number of different fields including physics, computer science, and engineering. Some notable figures in the development of quantum computing include:

- David Deutsch, a physicist at the University of Oxford, proposed the first quantum algorithm in 1985.
- Peter Shor, a mathematician at MIT, developed the first quantum algorithm for factoring integers in 1994.
- David DiVincenzo, a physicist at IBM, laid out the physical requirements for building a quantum computer in 2000.

It’s important to note that the development of a practical, working quantum computer is an ongoing effort, many organizations and researchers across the world are working to develop and improve the technology.

### How does quantum computing works ?

A quantum computer works by using quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data.

A quantum computer uses quantum bits, or qubits, which can exist in multiple states at once. This allows a quantum computer to perform certain types of calculations much faster than classical computers. A qubit can exist in a superposition of states, meaning it can be in multiple states at the same time, allowing it to perform several calculations simultaneously.

One of the key ways that quantum computers perform these calculations is through the use of quantum gates, which are the equivalent of transistors in classical computers. Quantum gates allow a quantum computer to manipulate the state of a qubit, which is the basic building block of quantum computing.

A quantum computer also uses quantum algorithms, which are specific sets of instructions for manipulating qubits in order to perform a specific task. These algorithms take advantage of the unique properties of qubits and quantum gates to perform tasks that would be difficult or impossible for classical computers to do.

Another important aspect of quantum computing is quantum error correction. Because qubits are highly sensitive to their environment and can be easily disturbed, quantum error correction is used to detect and correct errors that occur during computation. This is crucial for preserving the integrity of the data being processed by the quantum computer and ensuring the accuracy of the calculations.

In summary, a quantum computer works by using qubits to perform calculations, which can exist in multiple states at once and manipulate them with quantum gates, and use quantum algorithms to perform specific tasks, while using error correction techniques to preserve the integrity of the computation.

### Uses of Quantum Computers

- Drug discovery and materials science: Quantum computers can be used to simulate complex chemical reactions and predict the properties of new materials.
- Cryptography: Quantum computers can be used to break traditional encryption methods, but they also have the potential to create new, unbreakable forms of encryption.
- Financial modeling: Quantum computers can be used to solve complex optimization problems, which could have applications in portfolio optimization and risk analysis.
- Machine learning: Quantum computers can be used to train large neural networks and perform other machine learning tasks more efficiently.
- Artificial intelligence: Quantum computers can be used to perform large-scale optimization and sampling tasks which are useful in AI applications.
- Weather forecasting: Quantum computers can be used to simulate the behavior of complex systems such as the atmosphere, to improve weather forecasting.

### Companies Using Quantum Computers

Several companies are currently researching and developing quantum computers, including:

- IBM: IBM has been actively researching quantum computing for several decades and has developed a number of quantum computing platforms, including the IBM Q Experience and IBM Q Network.
- Google: Google has been working on quantum computing for several years and in 2017, announced the development of a quantum computer that had achieved “quantum supremacy,” meaning it could perform certain calculations that would be practically impossible for a classical computer.
- Rigetti Computing: Rigetti Computing is a company that designs and manufactures quantum computing hardware and software. They provide cloud-based access to their quantum processors via their Forest platform.
- IonQ: IonQ is a company that develops trapped-ion quantum computers. They provide cloud-based access to their processors via their IonQ Cloud platform.
- Alibaba: Alibaba is a Chinese multinational conglomerate holding company specializing in e-commerce, retail, internet, and technology. They also have their own quantum lab and have been investing in quantum technology for a few years.
- Honeywell: Honeywell is an American multinational conglomerate that produces a wide variety of commercial and consumer products, engineering services and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments. They have recently announced their own trapped-ion quantum computer.

Note that this list is not exhaustive, and there are many other companies, startups and research institutions that are also working on quantum computers.