Support for the powering modifier of OpenQASM 3.0 #27
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Bumps [extern/googletest](https://github.com/google/googletest) from `bea621c` to `7735334`. - [Release notes](https://github.com/google/googletest/releases) - [Commits](google/googletest@bea621c...7735334) --- updated-dependencies: - dependency-name: extern/googletest dependency-type: direct:production ... Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
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This PR replaces the existing OpenQASM 2.0 parser with a new OpenQASM
3.0 parser.
The new parser now builds a syntax tree, where type checking, constant
evaluation, and translation to the Quantum circuit.
The parser can handle the following new features:
### New Syntax
New syntax for declaring bits, qubit, measure operations. The old syntax
(`creg`, `qreg`) is still supported.
```qasm
qubit[8] q;
bit[8] c;
c[0] = measure q[0];
measure q[1] -> c[1];
if (c[0] == 1) {
x q[0];
}
```
### Gate modifiers
Gate modifiers (`inv`, `ctrl`, and `negctrl`) are now supported. This
replaces the `c` prefix.
See the OpenQASM 3.0 specification for more information:
https://openqasm.com/language/gates.html#quantum-gate-modifiers
```qasm
ctrl @ x q[0], q[1]; // Equivalent to cx q
ctrl(2) @ x q[0], q[1], q[2]; // Equivalent to ccx q;
```
### Classical constant values
The parser now supports classical computation with constant values. This
can be used to e.g. define the number of quantum registers.
```qasm
const uint N = 4;
qubit[N * 2];
x qubit[N * 2 - 1];
```
Additionally, all features of the previous parser are still supported.
The big features from OpenQASM 3.0 still missing are:
- classical computational features such as loops, functions, etc. (see
#33)
- types such as bools, floats, angles, complex types, etc. (see #30,
#32)
- `pow` modifier (#27)
---------
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Lukas Burgholzer <burgholzer@me.com>
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The new OpenQASM standard introduces gate modifiers in order to more efficiently describe quantum circuits. Any modifier
modcan be applied to a gategviamod @ g. For more details, see Section 4.2 in https://arxiv.org/pdf/2104.14722.pdf or the Live Specification.The powering modifier
pow(r)can be used to represent the r-th power of any gategviapow(r) @ g, wherercan either be an integer or a floating point number.The case where
ris a floating point number needs to be handled by computing the principal logarithm of the unitary that representsg. This might be tricky in general.The case where
ris an integer can be naively solved by repeatedly applyingg. Ifr <0,pow(r) @ gcan be translated toinv @ pow(-r) @ g. Several simplification might be possible here, e.g., the powers of phase gates can easily be computed by appropriately scaling the respective parameter. In its simplest formpow(2) @ s = z.At the very least, support for the case where
ris an integer shall be provided which provides much greater flexibility for describing circuits in a standardized way.Tasks
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