Classical vs. Quantum Bits

While the math for the total number of combinations is the same for both classical bits and qubits, how they hold that information is entirely different:

• Classical Bits: A 100-bit classical register can only hold one of those $2^{100}$ combinations at any single point in time (e.g., just the string 01101...).
• Quantum Qubits: Thanks to superposition and entanglement, a 100-qubit system can exist in a mathematical blend of all 2^100 states simultaneously.

1 electron represents 1 qubit.

An electron acts like a tiny, microscopic bar magnet. When you place it inside a magnetic field, its spin orientation can only point in one of two directions:

• State |0> (the ground state): Spin-Down (aligned with the magnetic field, which is its lowest energy state). This state represents a classical bit 0.

• State |1> (the excited state): Spin-Up (pointing against the magnetic field, a higher energy state). This state represents a classical bit 1.

In quantum computing, we map these spatial directions to mathematical states using a tool called the Bloch Sphere. By convention, the Z-axis is chosen as our standard computational baseline (our classical 0 and 1).