Quantum Computing is a field of computing that is centered on creating such computer systems that function based on quantum theory. And the computers that carry out quantum computing are called quantum computers. They store data and perform computation based on quantum mechanics. They can perform tasks, which present day classical computers cannot do due to the complexity of the task even those tasks to be performed within lesser than few seconds. These computers are completely different from classical computers.

Before we give more detail about **what is quantum computing and how quantum computers works** let us first understand how a classical computer works:

The Classical day to day computers that we use right now processes its functions on the basis of binary computing. In a classical computer, information is stored in the form of binary digits which are popularly known as bits, these bits are generally represented by either a 0(off) or a 1(on). Binary digit system is used inside a computer to transfer and process information. Therefore, it is safe to say that bits is the basic unit of classic computing.

Now on the other hand, here’s **how a quantum computer works or how a quantum computer functions** :

Unlike a classical computer, in a quantum computer each bit of information carried out by it is called a quantum bit or popularly known as qubit. A qubit can represent 0,1 or any value between them at the same time(for eg.70%=0 and 30%=1). The state of holding both values 0 and 1 at the same time is called bi-stable/superposed state in quantum system.

To understand quantum computing one must become familiar with the following phenomena that play an important role in building quantum computational theory:

- Superposition – Superposition is a basic principle of quantum mechanics. Superposition is a condition in which any two or more quantum states can be superposed together and the outcome will be another appropriate quantum state. In quantum computing, a qubit may be in a superposition of both 0 and 1 states.

- Entanglement – Another notable phenomenon in quantum computing is entanglement. Entanglement is when two particles, such as photon or qubit, interact and adapt in such a relationship in which neither is there a physical or controllable exchange between the particles. If two particles are entangled then any alteration made in the superposition state of one of the particle will correspond to alterations in the superposition state of other particle. Two entangled particles do not even require any stimulation to do so. This process is extremely fast, the speed of this process outpowers even the speed of light, despite of the large distances that separate the two particles.

- Quantum Parallelism – The phenomenon of superposition arises the concept of quantum parallelism to create new quantum microprocessors. The principle of quantum parallelism allows multiple calculations to be performed at the same time. Thus, quantum computers can perform the multiple calculations simultaneously. Through, parallelism complex calculations such as factorization of large numbers, as large as a 500-digit number, can be performed way faster than supercomputers.

Here is a tabular depiction of the difference between classical computers and quantum computers:

Challenges of building Quantum Computers:

- Quantum Computers are very difficult to engineer, program and build because of the particular conditions that it requires to function.

- The coupling together of qubits and the need of measuring their states, which is necessary for the computation process, produces excessive noise.

- Decoherence is another big hurdle that is as of now unavoidable in the quantum computing world. Decoherence is when the quantum information outspreads outside the quantum computer and gets lost in the environment which spoils the computation. Decoherence can be caused due to vibrations, electromagnetic waves and other interactions with the environment. This ultimately results in the destruction of exotic quantum properties of the computer.

- Another big hurdle is temperature restrictions. A quantum computer needs to be kept in a certain cold temperature to function properly. For instance take the example of the IBM quantum computer called “IBM Q SYSTEM ONE”. IBMQ is the first commercial quantum computer. The IBMQ or any other quantum computer needs to be kept in temperature as low as 15 millikelvin in a dilution refrigerator to prevent or minimize the heat that can excite the superconducting qubit and can result in errors and faults.

- The qubits are incredibly powerful but are also very delicate which arise many problems as these delicate qubits may lose their special quantum properties, typically within 100 microseconds, due to any unwanted external disturbance or force.

But besides all these difficulties there is no denial of the fact that quantum computing will one day be a transformative reality. The following are some possible applications of quantum computing:

- Molecular Modeling – Chemical reactions are quantum in nature . Quantum chemistry is so complex that today’s digital computers can only analyze simplest molecules but with the emergence of quantum computers the modeling of molecular interactions and finding the best configurations for chemical reactions can be done very efficiently and easily.

- Cryptography – Majority of the online security depends on the difficulty of factoring large numbers into primes. Although, this can be performed by digital computers but the process becomes very expensive, impractical, and time consuming. But, with quantum computers such factoring can be performed efficiently and comparatively quickly.

- Weather Forecasting – Weather directly or indirectly impacts many fields such as transportation, food production, disaster prediction etc. Thus, weather forecast becomes extremely important. Weather forecast models that we use now-a-days works on the basis of classical computers. Often these forecasts are inaccurate and very time consuming but quantum computers could help build better climate models.

- Drug design and development – designing and developing drug is a pretty complex process. Generally, these drugs are developed via trial and error method. This process is not only time consuming and expensive but is also very risky. But with the emergence of quantum computing the researchers believe that quantum computing can be a notable way of understanding drugs and its reactions on humans. This may not only save money but also time for drug companies.

Quantum Computing is a very innovative and useful approach that people should be more aware about. With the ongoing research it is sure that one day Quantum Computing will become a part of our daily lives.

What are your views on quantum computing? Is it any good?

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