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What is Quantum Supremacy claimed by Google? [Mains Articles]

Quantum supremacy is a milestone that has been long sought in computing, and now Google has announced it has reached it. A look at the science behind the concept, and what was really achieved and how much remains.
By IT's Mains Articles Team
October 30, 2019


  • Why it was in news?
  • What is Quantum Computer?
  • What is Quantum Supremacy?
  • Difference between process of Quantum computer and Classical computer?
  • Why currently it is not practical to use quantum computers?
  • Conclusion

What is Quantum Supremacy claimed by Google?

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Why it was in news?

  • Recently, Google announced that it had reached quantum supremacy. Google’s quantum computer, called Sycamore which is a 54-qubit processor, solved a particularly difficult problem in 200 seconds.


  • For comparison, the world’s current fastest classical computer — one called Summit owned by IBM would take 10,000 years to solve that same problem. However, IBM has said that the same task can be performed on a classical system in 2.5 days.
  • Although Sycamore performed a benchmark test, it has no real-world use. Even if it has demonstrated quantum supremacy, it could take years or decades for the technology to be freely available.

What is Quantum Computer?


  • Quantum computer runs on the laws of quantum physics as opposed to the classical computers (i.e. phones and laptops), which run on classical physics like Newton’s laws of motion and utilising the flow of electricity.
  • A quantum computer uses the laws that govern the behaviour of atoms and subatomic particles. At that tiny scale, many laws of classical physics do not apply, and the unique laws of quantum physics come into play.
  • The quantum computer was posited by Richard Feynman for modelling quantum systems.


Quantum Supremacy

  • Use in labs for modelling systems, under extreme conditions, like in the Large Hadron Collider (LHC).
  • Data mining and artificial intelligence
  • Sciences which deal in volumes of data
  • Optimization, planning, and logistics
  • Forecasting
  • Financial modelling and Molecular modelling
  • Genomics, Drug design and discovery
  • Cybersecurity and cryptography

What is Quantum Supremacy?

Quantum Supremacy 1

  • Quantum supremacy describes the point where quantum computers can do things that classical computers cannot.
  • This term was proposed in 2012 by John Preskill, professor of theoretical physics at the California Institute of Technology.

Difference between process of Quantum computer and Classical computer?


  • In classical computer, information is stored as either 0 or 1. Every string of such digits (bitstrings) represents a unique character or instruction. For example, 01100001 represents the lowercase “a”.
  • In a quantum computer, information is stored in quantum bits or qubits. A qubit can be both 0 and 1 at the same time.
  • The higher the number of qubits, the higher the amount of information stored in them. Qubits are made of tiny loops of superconducting wire or semiconductors or combination of both.
  • Unlike classical physics, in which an object can exist in one place at one time, quantum physics looks at the probabilities of an object being at different points. Existence in multiple states is called superposition.
  • In designing a standard computer, each bit is independent from that of all the other bits. But in a quantum computer, each qubit influences the other qubits around it, working together to arrive at a solution. These relationships among these states is called entanglement.
  • The reason why quantum computer is so powerful than the classical computer is that the large amount of information can be stored in quantum computers compared to classical computers.

Why currently it is not practical to use quantum computers?

  • Scientists have only been able to keep qubits in a quantum state for fractions of a second.
  • Generation of errors as qubits fall out of a quantum state. To remove error, more number of qubits are needed, but this can consume so much power that it negates the advantage of using a quantum computer.

Threat from Quantum computers

  • The security of communications, bank accounts and other sensitive data depends on public-key cryptography.
  • At the core of this approach is the fact that factoring very large prime numbers takes a long time. For example, 589 is the result of multiplying two primes: 19 and 31 together. Multiplying two numbers is a mathematically easy problem. However, factoring numbers is a computationally difficult problem especially when numbers are big. This is because computer have to try all of the primes that are less than 589 until it found which prime numbers that when multiplied together come to 589.
  • However, with such fast quantum computers, the online privacy can be compromised.


  • Quantum computers could one day result in huge advances in science research and technology. Among areas that stand to gain are artificial intelligence, and new drug therapies. All that, however, is a long way away.


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