The CZ Gate

The controlled-Z gate is a two-qubit entangler native to much of today's hardware - and entanglement is what makes Kronos's material-simulation circuits more than a stack of single qubits.

What it does

CZ leaves |00>, |01>, |10> alone and sends |11> to -|11>, symmetric between control and target. A CNOT is just a CZ wrapped in Hadamards, so a device that runs CZ natively is universal with a single-qubit set.

Where it appears at Kronos

The correlations between electrons in a molecule are exactly what classical methods struggle with; CZ and its cousins inject that entanglement into Kronos's chemistry circuits. On the hardware Kronos benchmarks, CZ fidelity is a direct limit on how large a material can be simulated.

Honest note

Two-qubit error rates are today's bottleneck; the fusion-materials payoff waits on error correction, ~mid-2030s.