cherry-pick minor bugfixes from master #4807
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We discovered a difference between `default.qubit` and
`default.qubit.legacy` over their treatment of the evolution of
hamiltonians:
```python
dev = qml.device('default.qubit', wires=3)
coeffs = [0.1, 0.2]
operators = [qml.PauliZ(0) @ qml.PauliZ(1), qml.PauliZ(0) @ qml.PauliZ(2)]
hamiltonian = qml.Hamiltonian(coeffs, operators)
@qml.qnode(dev)
def f():
qml.evolve(hamiltonian, 0.5)
return qml.density_matrix([0])
f()
```
Previously `qml.evolve(hamiltonain, t)` worked because `Evolution` was
hardcoded as an accepted observable. This meant it became an accepted
operation as well, even though it stated it didn't have a matrix.
In `ScalarSymbolicOp`, the parent for `Evolution`, we added a special
logical pathway for the matrix if the target is a Hamiltonian, but we
didn't include that special logical pathway for the `has_matrix`
property.
This PR updates the `has_matrix` property for and allows the evolution
of a hamiltonian to execute on `default.qubit`.
**Warning:**
This matrix is not backprop compatible.
```
dev = qml.device('default.qubit.legacy', wires=3)
coeffs = [0.1, 0.2]
operators = [qml.PauliZ(0) @ qml.PauliZ(1), qml.PauliZ(0) @ qml.PauliZ(2)]
@qml.qnode(dev)
def f(x):
hamiltonian = qml.Hamiltonian(x, operators)
qml.evolve(hamiltonian, 0.5)
return qml.density_matrix([0])
qml.grad(f)(qml.numpy.array(coeffs))
```
Gives
```
AttributeError: 'ArrayBox' object has no attribute 'tocsr'
```
`qml.dot` and operator arithemetic does not have these problems.
---------
Co-authored-by: lillian542 <38584660+lillian542@users.noreply.github.com>
Fixes #4779 . [sc-49381] When creating an initial state, `get_final_state` was using `tape.op_wires` for the wire order, even though the simulation always occurred using the wire order `(0,1,2,3,...)`. Sometimes `tape.op_wires` would have a different order, leading to a mismatch. Now we use `sorted(circuit.op_wires)`, so they will always be in the monotonically increasing integers used by the simulation. --------- Co-authored-by: Matthew Silverman <matthews@xanadu.ai> Co-authored-by: Tom Bromley <49409390+trbromley@users.noreply.github.com>
…uit measurements (#4787) **Context:** When making terminal measurements on wires with mid-circuit measurements, the circuit was not being transformed correctly. This PR fixes that. **Description of the Change:** Wires are considered to be reused by `defer_measurements` when a measured wire has operators *and* terminal measurements applied to it after mid-circuit measurements. **Benefits:** **Possible Drawbacks:** **Related GitHub Issues:** [sc-49507]
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## v0.33.1-rc0 #4807 +/- ##
===============================================
- Coverage 99.64% 99.64% -0.01%
===============================================
Files 380 380
Lines 34266 34009 -257
===============================================
- Hits 34145 33887 -258
- Misses 121 122 +1
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albi3ro
approved these changes
Nov 8, 2023
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Context:
These three bugs were identified as good to be released in a bugfix.
Description of the Change:
Cherry-pick the 3 commits to master onto this branch for the 0.33.1 bugfix release
Benefits:
Fixed bugs pushed out!
Possible Drawbacks:
Extra work in a critical time.
Related GitHub Issues:
#4768, #4781, #4787