The IBM Q architecture provides the following physical gates (primitives).
| QASM | Name | Qubit Count | Parameter Count |
|---|---|---|---|
| reset | Reset | 1 | 0 |
| U | Universal | 1 | 3 |
| CX | Controlled Not | 2 | 0 |
| measure | Measure | 1 | 0 |
Reset is a separate instruction, but can theoretically be implemented as
measure q b;
if (b == 1) x q;
where x is U(PI,0,PI) and PI is a half rotation (π).
The universal single-qubit instruction takes 3 parameters. Here the question is the theoretical precision (value space) of these parameters and the physical precision (tolerance) of their implementation in hardware.