Add documentation on OpenQASM 2 phase conventions #10801
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OpenQASM 2 as a language does not provide a way to specify global phases, either of operations or the entire program. The prose of the defining paper talks about the `u1` and `rz` instructions from `qelib1.inc` as having different global phases, however since the language cannot represent this, the header file defines `rz` apparently as a direct alias to `u1`. Qiskit's position has always been that we interpret `rz` as using the phase convention of `RZGate`, and `u1` uses the different convention of `PhaseGate`. This commit adds documentation to the pages on OpenQASM 2 about this difference, and includes an example of how to override Qiskit's default if the generating code (e.g. pyZX) wants to use an alternative phase convention.
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Co-authored-by: Julien Gacon <gaconju@gmail.com>
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* Add documentation on OpenQASM 2 phase conventions OpenQASM 2 as a language does not provide a way to specify global phases, either of operations or the entire program. The prose of the defining paper talks about the `u1` and `rz` instructions from `qelib1.inc` as having different global phases, however since the language cannot represent this, the header file defines `rz` apparently as a direct alias to `u1`. Qiskit's position has always been that we interpret `rz` as using the phase convention of `RZGate`, and `u1` uses the different convention of `PhaseGate`. This commit adds documentation to the pages on OpenQASM 2 about this difference, and includes an example of how to override Qiskit's default if the generating code (e.g. pyZX) wants to use an alternative phase convention. * Comment on the number of overrides needed Co-authored-by: Julien Gacon <gaconju@gmail.com> --------- Co-authored-by: Julien Gacon <gaconju@gmail.com> (cherry picked from commit 10461f1)
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* Add documentation on OpenQASM 2 phase conventions OpenQASM 2 as a language does not provide a way to specify global phases, either of operations or the entire program. The prose of the defining paper talks about the `u1` and `rz` instructions from `qelib1.inc` as having different global phases, however since the language cannot represent this, the header file defines `rz` apparently as a direct alias to `u1`. Qiskit's position has always been that we interpret `rz` as using the phase convention of `RZGate`, and `u1` uses the different convention of `PhaseGate`. This commit adds documentation to the pages on OpenQASM 2 about this difference, and includes an example of how to override Qiskit's default if the generating code (e.g. pyZX) wants to use an alternative phase convention. * Comment on the number of overrides needed Co-authored-by: Julien Gacon <gaconju@gmail.com> --------- Co-authored-by: Julien Gacon <gaconju@gmail.com> (cherry picked from commit 10461f1) Co-authored-by: Jake Lishman <jake.lishman@ibm.com>
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* Add documentation on OpenQASM 2 phase conventions OpenQASM 2 as a language does not provide a way to specify global phases, either of operations or the entire program. The prose of the defining paper talks about the `u1` and `rz` instructions from `qelib1.inc` as having different global phases, however since the language cannot represent this, the header file defines `rz` apparently as a direct alias to `u1`. Qiskit's position has always been that we interpret `rz` as using the phase convention of `RZGate`, and `u1` uses the different convention of `PhaseGate`. This commit adds documentation to the pages on OpenQASM 2 about this difference, and includes an example of how to override Qiskit's default if the generating code (e.g. pyZX) wants to use an alternative phase convention. * Comment on the number of overrides needed Co-authored-by: Julien Gacon <gaconju@gmail.com> --------- Co-authored-by: Julien Gacon <gaconju@gmail.com>
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Summary
OpenQASM 2 as a language does not provide a way to specify global phases, either of operations or the entire program. The prose of the defining paper talks about the
u1andrzinstructions fromqelib1.incas having different global phases, however since the language cannot represent this, the header file definesrzapparently as a direct alias tou1.Qiskit's position has always been that we interpret
rzas using the phase convention ofRZGate, andu1uses the different convention ofPhaseGate. This commit adds documentation to the pages on OpenQASM 2 about this difference, and includes an example of how to override Qiskit's default if the generating code (e.g. pyZX) wants to use an alternative phase convention.Details and comments
See the discussion in #10790.
Also I fixed a couple of typos that have been annoying me in the documentation, since I had it open.