Summary
A qubit is like a bit, except that a qubit’s value can be between |0⟩ and |1⟩. What between means requires more explanation but, in this chapter, we described between in a statistical fashion.
There’s no way for us to determine that a single qubit’s state is between |0⟩ and |1⟩. Instead, being halfway between |0⟩ and |1⟩ means that, if you measure many such qubits, you get 0 approximately half the time and 1 all the other times. All we can do is record these measurement tallies. As my friend and colleague, Ashley Carter, once said, “Quantum mechanics isn’t about what “is.” Quantum mechanics is about what we can measure.”
In the next chapter, we’ll use mathematics to describe qubits more precisely.
