The difference between an ordinary computer (classical computer) and a quantum computer lies in their underlying principles and the way they process information.
Classical computers, which include the devices we commonly use today, process information using classical bits. A classical bit can represent either a 0 or a 1. Classical computers perform calculations by manipulating these bits through logic gates and algorithms. They process information sequentially, executing instructions one after the other, and their computational power scales with the number of classical bits they have.
Quantum computers, on the other hand, leverage the principles of quantum mechanics to process information. Instead of classical bits, they use quantum bits or qubits. Qubits can represent a 0, a 1, or a superposition of both simultaneously due to a property called superposition. Additionally, qubits can be entangled, which means the state of one qubit is dependent on the state of another, regardless of the physical distance between them.
This unique property of superposition and entanglement allows quantum computers to perform certain calculations more efficiently than classical computers for specific problems. Quantum computers can leverage parallelism by manipulating multiple qubits simultaneously, potentially exploring many possible solutions in parallel. This parallelism can lead to exponential speedup for certain algorithms, such as factoring large numbers using Shor's algorithm or solving optimization problems using quantum annealing.
However, it's important to note that quantum computers are not inherently faster than classical computers for all types of problems. While they can offer significant speedup for specific applications, there are still many problems for which classical computers remain more efficient. Additionally, quantum computers are currently in their early stages of development, and building large-scale, error-corrected quantum computers is still a significant technical challenge.