ABSTRACT
Quantum computing is the area of study focused on developing computer technology based on the principles of quantum theory. As we progress to smaller and faster circuits, we begin to reach the physical limits of materials and the threshold for classical laws of physics to apply. Classical computers use transistors as the physical building blocks of logic, while quantum computers may use trapped ions, superconducting loops, quantum dots or vacancies in a diamond. Physical qubits are the physical qubits in a quantum computer, whereas logical qubits are groups of physical qubits we use as a single qubit in our computation to fight noise and improve error correction. There are many estimates as to how many qubits the authors will need to perform certain calculations, but some of these estimates talk about logical qubits and others talk about physical qubits. For example, to break RSA cryptography we would need thousands of logical qubits but millions of physical qubits.
