Quantum Computing: Beyond One Qubit
Open Source For You, Thursday, October 15th, 2026
Part four of a quantum series explains why superconducting qubits are error-prone and introduces the multi-qubit CNOT gate.
The fourth article in OSFY's quantum computing series moves from single-qubit gates, explored earlier with a Bloch sphere simulator, to multi-qubit systems and the Controlled-NOT (CNOT) gate.
It first explains why real superconducting hardware is error-prone: qubits built on Josephson junctions must preserve fragile states that thermal radiation, stray fields, material defects, cosmic rays and vibrations can destroy through decoherence.
Engineers counter this with nanofabrication, dilution refrigerators at a few millikelvin and precisely shaped microwave pulses.
This is why algorithms that work on ideal simulators can fail on real machines.