Physical vs Logical - Physical qubits are the, well, physical qubits in our computer – the number of qubits on the box, whereas logical qubits are groups of physical qubits we use as a single qubit in our computation - Physical qubits are prone to noise. Because of this noise, we can use multiple physical qubits to form a single more stable logical qubit. - Usable / noise adjusted / error corrected physical qubits coupled together to form a logical qubit - Quantum algorithms use logical qubits #### Quantum Computational Power = number of logical qubits (which are loosely equivalent to the number of bits and memory in a traditional processor) + the much higher number of physical qubits to handle error correction (more on this below). --- A qubit is a bit that has a **complex number** called an [[Amplitudes]] attached to the possibility that it’s 0, and a different amplitude attached to the possibility that it’s 1. These [[Amplitudes]] are closely related to probabilities, in that the further some outcome’s amplitude is from zero, the larger the chance of seeing that outcome; more precisely, **the probability equals the distance squared.**