We’ve been using computers since the early 19th century. We’re currently in the fourth generation of computers with the microprocessors after vacuum tubes, transistors, and integrated circuits. They were all based on conventional computing technology which is based on the classical phenomenon of electrical circuits being in a single state at a given time, either on or off.

“The fifth generation of computers is currently under development of which quantum computing or quantum computers are most popular. Quantum computers are totally different from conventional computers on how they work”.

Quantum computer

Quantum computers are based on the phenomenon of Quantum Mechanics, the phenomenon where it is possible to be in more than one state at a time. Computers are getting smaller and faster day by day because electronic components are getting smaller and smaller. But this process is about to meet its physical limit.

Electricity is the flow of electrons. Since the size of transistors is shrinking to the size of a few atoms, transistors cannot be used as a switch because electrons may transfer themselves to the other side of blocked passage by the process called quantum tunnelling.

Quantum mechanics is a branch of physics that explores the physical world at the most fundamental levels. At this level, the particle behaves differently from the classical world taking more than one state at the same time and interacting with other particles that are very far away. Phenomena like superposition and entanglement take place.

What are quantum computers?

Computing technology

Quantum computers work differently from classical computers we work on today. Exploiting the principles of quantum mechanics, they can easily tackle computational problems that may be tough for the classical computer as the size of the numbers and number of inputs involved grows bigger.

Quantum computers do not look like desktops or laptops that we associate the word ‘computer’ with. Instead (and there is only a handful of them) they resemble the air-conditioned server rooms of many offices or the stacks of central processing units from desktops of yore that are connected by ungainly tangled wires and heaped in freezing rooms.

“Conventional computer technology process information in ‘bits’ or 1s and 0s, following classical physics under which our computers can process a ‘1’ or a ‘0’ at a time”. 

The world’s most powerful supercomputer today can juggle 148,000 trillion operations in a second and requires about 9000 IBM CPUs connected in a particular combination to achieve this feat. Quantum computers compute in ‘qubits’ (or quantum bits). They exploit the properties of quantum mechanics, the science that governs how matter behaves on the atomic scale.

Modern chip technology

In this scheme of things, processors can be a 1 and a 0 simultaneously, a state called quantum superposition. While this accelerates the speed of computation, a machine with less than 100 qubits can solve problems with a lot of data that are even theoretically beyond the capabilities of the most powerful supercomputers.

Because of quantum superposition, a quantum computer if it works to plan can mimic several classical computers working in parallel. The ideas governing quantum computers have been around since the 1990s but actual machines have been around since 2011, most notably built by Canadian company D-Wave Systems.

What can quantum computers do?

Quantum computers can easily crack the encryption algorithms used today in very less time whereas it takes billions of years to best supercomputer available today. Even though quantum computers would be able to crack many of today’s encryption techniques, predictions are that they would create hack-proof replacements. Quantum computers are great for solving optimization problems.

Difference between conventional computing and quantum computing:



  • Conventional computing technology is based on the classical phenomenon of electrical circuits being in a single state at a given time, either on or off.
  • Quantum computing is based on the phenomenon of Quantum Mechanics, such as superposition and entanglement, the phenomenon where it is possible to be in more than one state at a time.
  • Information storage and manipulation are based on “bit”, which is based on voltage or charge; low is 0 and high is 1.

  • Information storage and manipulation are based on Quantum Bit or “qubit”, which is based on the spin of an electron or polarization of a single photon.

  • The circuit behaviour is governed by classical physics.
  • The circuit behaviour is governed by quantum physics or quantum mechanics.

  • Conventional computing uses binary codes i.e. bits 0 or 1 to represent information.


  • Quantum computing technology uses Qubits i.e. 0, 1 and superposition state of both 0 and 1 to represent information.
  • CMOS transistors are the basic building blocks of conventional computers.

  • Superconducting Quantum Interference Device or SQUID or Quantum Transistors are the basic building blocks of quantum computers.

  • In conventional computers, data processing is done in the Central Processing Unit or CPU, which consists of Arithmetic and Logic Unit (ALU), processor registers and a control unit.
  • In quantum computers, data processing is done in the Quantum Processing Unit or QPU, which consists of a number of interconnected qubits.

What is the latest and highest technology in quantum computing?

Quantum computer technology

Quantum supremacy refers to quantum computers being able to solve a problem that a classical computer cannot.

In the research paper, Google used a 53-qubit processor to generate a sequence of millions of numbers. Though these numbers appeared randomly generated, they conform to an algorithm generated by Google.

“A classical supercomputer checked some of these values and they were correct”.

Google’s quantum computer, named Sycamore, claimed ‘supremacy’ because it reportedly did the task in 200 seconds that would have apparently taken a supercomputer 10,000 years to complete.

Future of Quantum Computing technology:

future of quantum computer technology

Quantum computing has great potential for the future. You perhaps noticed that present-day information processing and storage needs increment of the bits registers more and more (eg. 32 bits, 64 bits) also information storages (10TB, etc ) quantum computing technology will allow a very large amount of information storage with a very small number of qubits.

Qubit will help in solving very complex computation problems like turbulence, many-body problems, etc. Quantum computing technology will destroy any “secure” present-day encryption like AES-256 easily by its ability to determine very large prime numbers in a short time (Shor’s algorithm is one example). Following is the hypothetical pathway for the future of quantum computing comprising Rose’s law.

Is India working on quantum computing technology?

Quantum computing technology

There are no quantum computers in India yet. In 2018, the Department of Science & Technology unveiled a program called Quantum-Enabled Science & Technology (QuEST) and committed to investing ₹80 crores over the next three years to accelerate research. The ostensible plan is to have a quantum computer built in India within the next decade. Phase-1 of the problem involves hiring research experts and establishing teams with the know-how to physically build such systems.


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