IAS Gyan



5th November, 2021 Prelims


What is quantum computing?

Let’s start with the basics.

  • An ordinary computer chip uses bits. These are like tiny switches that can either be in the off position – represented by a zero – or in the on position – represented by a one.
  • Every app we use, website we visit and photograph we take is ultimately made up of millions of these bits in some combination of ones and zeroes.
  • This works great for most things, but it doesn’t reflect the way the universe actually works.
  • In nature, things aren’t just on or off. They’re uncertain. And even our best supercomputers aren’t very good at dealing with uncertainty. That’s a problem.
  • So, for scientists to accurately simulate any of those things, they need a better way of making calculations that can handle uncertainty. Enters - Quantum Computers.


How do quantum computers work?

  • Instead of bits, quantum computers use qubits. Rather than just being on or off, qubits can also be in what’s called ‘superposition’ – where they’re both on and off at the same time, or somewhere on a spectrum between the two.
  • Take a coin. If you flip it, it can either be heads or tails. But if you spin it – it’s got a chance of landing on heads, and a chance of landing on tails. Until you measure it, by stopping the coin, it can be either.
  • Superposition is like a spinning coin, and it’s one of the things that make quantum computers so powerful. A qubit allows for uncertainty.
  • If you ask a normal computer to figure its way out of a maze, it will try every single branch in turn, ruling them all out individually until it finds the right one.
  • A quantum computer can go down every path of the maze all at once. It can hold uncertainty in its head.
  • The other thing that qubits can do is called entanglement. Normally, if you flip two coins, the result of one coin toss has no bearing on the result of the other one. They’re independent. In entanglement, two particles are linked together, even if they’re physically separate. If one comes up heads, the other one will also be heads.
  • Quantum computing can be used to perform complex calculations. And if multiple qubits are stringed together, one can tackle problems that would take our best computers millions of years to solve.

Do you know?

Chinese scientists claim to have built a quantum computer that is able to perform certain computations nearly 100 trillion times faster than the world’s most advanced supercomputer.

Quantum Entanglement

  • Quantum entanglement is a physical phenomenon that occurs when a pair or group of particles is generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the pair or group cannot be described independently of the state of the others, including when the particles are separated by a large distance.
  • Measurements of physical properties such as position, momentum, spin, and polarization performed on entangled particles can, in some cases, be found to be perfectly correlated.
  • Quantum entanglement has direct application in Quantum Computing.