Quantum Computing

Introduction

Quantum Computing is a new paradigm of computing that uses the principles of quantum mechanics to process information. Unlike classical computers, which use bits (0 or 1), quantum computers use quantum bits (qubits) that can exist in multiple states simultaneously, enabling them to solve certain complex problems much faster than conventional computers.

Quantum computing has the potential to revolutionise fields such as cryptography, drug discovery, artificial intelligence, material science, finance and climate modelling.

Basic Principles of Quantum Computing

Quantum Bit (Qubit)

A qubit is the basic unit of quantum information.

Unlike a classical bit, which can be either 0 or 1, a qubit can exist in a superposition of both states simultaneously.

Examples of physical qubits include:

• Trapped ions
• Superconducting circuits
• Photons
• Neutral atoms
• Quantum dots

Superposition

Superposition allows a qubit to exist in multiple states at the same time until it is measured.

This enables a quantum computer to evaluate many possible solutions simultaneously, providing massive computational parallelism.

Entanglement

Quantum entanglement is a phenomenon in which two or more qubits become intrinsically linked, such that the state of one qubit instantly determines the state of the other, regardless of the distance separating them.

Entanglement allows quantum computers to perform coordinated computations beyond the capabilities of classical systems.

Quantum Interference

Quantum algorithms use interference to amplify the probability of correct solutions while suppressing incorrect ones, thereby increasing computational efficiency.

How Quantum Computers Differ from Classical Computers

Technologies Used

Major quantum computing technologies include:

• Superconducting qubits
• Trapped-ion quantum computers
• Photonic quantum computers
• Neutral atom quantum computers
• Topological quantum computing (under development)

Applications

Cryptography

Quantum computers can efficiently solve mathematical problems underlying many existing public-key cryptographic systems, such as RSA and Elliptic Curve Cryptography (ECC), necessitating the development of post-quantum cryptography.

Drug Discovery

They can simulate molecular interactions and protein structures more accurately, accelerating the discovery of new medicines and vaccines.

Artificial Intelligence

Quantum machine learning may improve:

• Pattern recognition.
• Optimisation.
• Large-scale data analysis.

Material Science

Quantum simulations can help design:

• Better batteries.
• High-temperature superconductors.
• Advanced semiconductors.
• Novel industrial materials.

Climate and Weather Modelling

Quantum computing can improve simulations of:

• Climate systems.
• Ocean circulation.
• Weather forecasting.
• Carbon capture technologies.

Finance

Applications include:

• Portfolio optimisation.
• Risk analysis.
• Fraud detection.
• Option pricing.

Logistics

Quantum optimisation can improve:

• Supply chain management.
• Traffic routing.
• Airline scheduling.
• Manufacturing processes.

Advantages

• Solves certain optimisation problems much faster than classical computers.
• Enables accurate simulation of quantum systems.
• Accelerates scientific research.
• Enhances artificial intelligence and machine learning.
• Improves complex decision-making and optimisation.

Challenges

Decoherence

Qubits lose their quantum properties when interacting with the external environment, introducing errors into computations.

Error Correction

Quantum systems are highly susceptible to noise, requiring sophisticated quantum error correction techniques and many physical qubits to create a single reliable logical qubit.

Cryogenic Requirements

Many quantum computers, especially those using superconducting qubits, must operate at temperatures close to absolute zero using liquid helium.

Scalability

Building large-scale, fault-tolerant quantum computers remains a significant engineering challenge.

High Cost

Quantum hardware is expensive to build, maintain and operate.

Quantum Computing in India

National Quantum Mission (NQM)

Launched in 2023 with an outlay of ₹6,003.65 crore for the period 2023–24 to 2030–31, the mission aims to establish India as a global leader in quantum technologies.

Objectives

• Develop intermediate-scale quantum computers with 50–1,000 physical qubits over the mission period.
• Advance quantum communication and secure quantum networks.
• Develop quantum sensors and metrology.
• Promote quantum materials and devices.
• Build a skilled quantum workforce and strengthen indigenous research.

Implementing Ministry

Department of Science and Technology (DST) under the Ministry of Science and Technology.

Major Areas

• Quantum Computing
• Quantum Communication
• Quantum Sensing
• Quantum Materials

Global Developments

Countries investing heavily in quantum technologies include:

• United States
• China
• European Union
• Canada
• Japan
• United Kingdom
• Australia

Leading companies include:

• IBM
• Google
• Microsoft
• Intel
• IonQ
• Rigetti
• Quantinuum

Significance

Quantum computing is considered a strategic frontier technology due to its potential impact on:

• National security.
• Defence.
• Cybersecurity.
• Scientific research.
• Healthcare.
• Economic competitiveness.
• Space technology.

Way Forward

• Increase investment in quantum research and indigenous hardware.
• Develop fault-tolerant and scalable quantum computers.
• Strengthen international collaboration.
• Accelerate development of post-quantum cryptography.
• Build quantum-ready human resources through education and research.
• Foster industry–academia partnerships to translate research into commercial applications.

Conclusion

Quantum computing represents a transformative leap beyond classical computing by harnessing the principles of quantum mechanics. Although large-scale practical quantum computers are still under development, their potential to solve previously intractable problems makes them one of the most strategically important technologies of the 21st century. For India, initiatives like the National Quantum Mission provide a significant opportunity to build indigenous capabilities, enhance technological self-reliance and emerge as a global leader in the quantum era.