Quantum Definitions: Quantum 101
Quantum bits (qubits) are a fundamental units or building blocks upon which quantum computers are based.
Qubits can exist in both states 0 and 1 simultaneously. Qubits exist in a probability, or superposition, of both zero and one until you measure or observe it.
Qubits can exist in both states 0 and 1 simultaneously. Qubits exist in a probability, or superposition, of both zero and one until you measure or observe it.
Qubits are complex, two-dimensional vectors. Hence, the state of a qubit is a continuum of two-dimensional complex vectors as compared to a bit which has two finite states of 0 and 1.
Image from: https://quantumatlas.umd.edu/entry/qubit
The state of a single qubit can be represented in complete generality by:
where 
References:
- Beginner's Guide to Quantum | Quantum 101: https://youtu.be/C74R5ZYjOFs?t=102
- What is a Qubit:
https://www.quantum-inspire.com/kbase/what-is-a-qubit/ - What is a Qubit: https://www.youtube.com/watch?v=zS0qkmkPSt0
- Qubit: https://en.wikipedia.org/wiki/Qubit
- The Quantum Atlas: Qubits:
https://quantumatlas.umd.edu/entry/qubit