The harness of collective properties of quantum states to perform computation is known as “**Quantum Computing**”. Quantum Computers are the devices that are used to perform quantum computation.

The story of quantum computers begins in the early 1980s with Paul Benioff (physicist) who proposed a quantum mechanical model of the Turing Machine. Later, Richard Feynman and Yuri Manin proposed that a quantum computer had the potential to simulate things a classical computer could not feasibly do.

Quantum computers are of different quantum circuit models, quantum Turing machines, adiabatic quantum computers, one-way quantum computers, and quantum cellular automata. But the most widely used model is the quantum circuit which is based on the quantum bit, or “qubit”. A qubit can be in a 1 or 0 quantum state. The probability of the outcome/output depends on the qubit’s quantum state immediately before measurement.

Quantum computers obey the Church Turing Thesis (It states that a function on the natural numbers can be calculated by an effective method if and only if it is computable by a Turing machine). Also, we can say that quantum computers do not provide any additional advantages over classical computers in terms of computability, but quantum algorithms for certain problems have significantly lower time complexities than corresponding known classical algorithms. quantum computers are believed to solve certain problems quickly than a classical computer, which could solve that certain problem in any *feasible* amount of time.

**What a quantum computer do today?**

**Navigation**– A GPS cannot work everywhere, especially underwater. A QC requires supercooled atoms which are suspended in a state that renders them particularly sensitive.**Seismology**-Extreme sensitivity is used to detect the presence of oil and gas deposits and potential seismic activity, where conventional sensors are unable to explore.

**Why do we need Quantum Computer?**

- Classical Computers use bits (either 0 or 1) for storing the information and with the help of these 2 bits, we can calculate Giga to Tera to Petabytes of data and even much more. Now, Four Classical Bits can be arranged in 2^4 combinations i.e, 16 combinations.
- CPU calculates at an average of 2.4GHz each combination at a time. Although, simultaneous calculations can be done by having more than 1 CPU in the machine that’s a different thing. The fact is that our CPU calculates each combination one at a time.

Here arises a big and advanced research question – can all of them be used simultaneously at once without having any multiprocessors?

That’s where Quantum Computers comes into the picture!!

**Will Quantum Computers replace our PCs?**

Classical computers have unique qualities that will be hard for Quantum Computers to attain. The ability to store data, Quantum Computers only lasts a few hundred microseconds at most. Quantum Computers need to be kept at temperatures close to absolute zero ~270 degrees Celsius (-450 degrees Fahrenheit). So, in Near Future Quantum Computers will not be feasible for common household and business purposes.

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