Overview

Quantum computing leverages quantum-mechanical phenomena—superposition, entanglement, and interference—to process information in ways fundamentally different from classical computers. While classical bits are binary (0 or 1), quantum bits (qubits) can exist in superposition of both states simultaneously.

How Qubits Work

A qubit is the basic unit of quantum information. Unlike classical bits, qubits exploit superposition to hold multiple values at once. When measured, a qubit collapses to a definite state. Entanglement links qubits so measuring one instantly determines the state of another, regardless of distance.

Current Hardware

Leading platforms include superconducting qubits (IBM, Google), trapped ions (IonQ, Quantinuum), photonic systems (Xanadu, PsiQuantum), and neutral atoms (QuEra, Atom Computing). Google's Sycamore achieved 'quantum supremacy' in 2019; IBM's 1,121-qubit Condor chip launched in 2023.

Practical Applications

Near-term applications include drug discovery (molecular simulation), optimization (logistics, finance), cryptography (post-quantum threats and defenses), machine learning acceleration, and materials science. Full-scale fault-tolerant quantum computing remains years away.

Challenges

Key obstacles include decoherence (qubit state loss), error rates, scalability of physical qubits, cryogenic cooling requirements for superconducting systems, and the need for quantum error correction which demands thousands of physical qubits per logical qubit.