Quantum Computing UPSC NOTE

 Quantum computing and how it is different from classical computing

  • Quantum computing harnesses the principles of quantum mechanics to perform calculations in a fundamentally different way compared to classical computers

Basics of Quantum Computing:

  • QubitsUnlike classical bits that can be either 0 or 1, quantum computers use qubits

  • These can exist in a state of superposition, meaning they can be both 0 and 1 simultaneously. This allows for parallel processing on a massive scale.

  • EntanglementQubits can be entangled, meaning

they are linked in a way that changes to one instantly affect the other, regardless of their distance. 

  • This enables powerful correlations and computations not possible with classical bits.

  • Quantum algorithms: These are specially designed instructions that leverage the capabilities of qubits and entanglement to solve problems more efficiently than classical algorithms for certain tasks.

Differences from Classical Computing:

  • Processing power: While classical computers rely on sequential processing, quantum computers can explore several possibilities simultaneously due to superposition and entanglement

  • This makes them potentially much faster for specific problems with numerous variables or combinations.

  • Problem typesClassical computers excel at tasks with well-defined rules and calculations, while quantum computers shine in problems involving probabilities, complex simulations, and optimizations

Basic concepts of  qubits, gates, and superposition 

Gate in computing

  • A bit is the smallest piece of information storage (it is a portmanteau of binary digit). Often, a large number of bits is required to convey meaningful information. 

  • With the advent of modern semiconductor technology, we routinely speak of household computers having a few terabytes (8 trillion bits) of information storage. 

  • One terabyte can store 500 hours of high-definition video content.

  • In a computer, a bit is a physical system with two easily discernible configurations, or states – e.g. high and low voltage. 

  • These physical bits are useful to represent and process expressions that involve 0s and 1s: for instance, low voltage can represent 0 and high voltage can represent 1.

  • A gate is a circuit that changes the states of bits in a predictable way

  • The speed at which these gates work determines how fast a computer functions.

The quantum gate

  • Modern computers use semiconductor transistors to build circuits that function as bits

  • A semiconductor chip hosts more than 100 million transistors on 1 sq. mm

  • Imagine how small an individual transistor is and how close it is to adjacent transistors

  • As transistors become smaller, they become more susceptible to quantum effects

  • This is not desirable as the existing technology will then become unreliable for computational tasks. 

  • Moore’s law, announced in 1965, states that computing power increases tenfold every five years

  • This law no longer holds as we have already slowed to a two-fold increase every five years.

  • But this doesn’t have to mean we are nearing the end of computing development: the quantum revolution is coming.

  • The most basic unit of a quantum computer is a quantum bit, or qubit

  • Like in a conventional computer, it is a physical object that has two states

  • For example, the spin of a particle can point along two different directions, so the particle can function as a qubit. 

  • Or it can be a superconducting circuit that mimics an atom, and its two states can be a ground state, where it has lower energy, and a higher ‘excited’ state.

  • Aquantum gateis a physical process or circuit that changes the state of a qubit or a collection of qubits.

  • In the quantum-computing context, if particles or superconducting qubits are the physical qubits, the gate is often an electromagnetic pulse.

Interlude: Superposition

  • A fundamental limitation of conventional computing architecture is that each bit can exist in only one of the two states, 0 or 1. 

  • But according to quantum physics, a qubit can also be in a superposition of its two states at the same time.

  • The basis states of the qubit are similar to the north and east directions. 

  • A qubit in a superposition has some contributions from each basis state

  • Different superpositions correspond to different amounts of contributions.

  • If a qubit is in a superposition, then measuring the qubit will cause it to collapse to one of the two states (i.e. either north or east). 

  • However, we can only predict the probability that it will collapse to one state

  • Superposition is one of the main factors responsible for speeding up a quantum computer.

  • But while superposition provides enormous advantages, it is a fragile effect

  • It deteriorates when qubits interact with their environment. 

  • Identifying ways to sidestep or overcome this fragility is an active area of research today.



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Learnerz IAS | Concept oriented UPSC Classes in Malayalam: Quantum Computing UPSC NOTE
Quantum Computing UPSC NOTE
Learnerz IAS | Concept oriented UPSC Classes in Malayalam
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