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Replace shallow copy with deepcopy in QV circuit generation #462
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In qiskit-community#460 we migrated the QV circuit generation to use the QV circuit from terra's circuit library instead of constructing it from scratch. As part of that the circuit generation was updated to construct a single virtual circuit via the library and just copy it for the no measure output circuits. However, this was done using a shallow copy (in the interest of performance) which means that any references between the circuits will not be duplicated. For cases where the qubit_lists input is not a contiguous list this would result in the measurements showing up in the no measurement circuits because of shared references. This commit fixes this by using deepcopy instead of a shallow copy so that there are no shared references between the measurement circuit and the no measurement circuit.
The seed parameter beign passed directly to the QuantumVolume circuit library resulted in the generated circuits all being identical. To ensure that we get reproducible but useful output this changes the seed usage to create it's own random Generator and use the seed parameter as the seed for that. Then the generator is used to generate a sequence of random integers which get passed to each QuantumVolume object.
chriseclectic
approved these changes
Aug 5, 2020
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Summary
In #460 we migrated the QV circuit generation to use the QV circuit from
terra's circuit library instead of constructing it from scratch. As part
of that the circuit generation was updated to construct a single virtual
circuit via the library and just copy it for the no measure output
circuits. However, this was done using a shallow copy (in the interest
of performance) which means that any references between the circuits
will not be duplicated. For cases where the
qubit_listsinput is not acontiguous list this would result in the measurements showing up in the
no measurement circuits because of shared references. This commit fixes
this by using deepcopy instead of a shallow copy so that there are no
shared references between the measurement circuit and the no measurement
circuit.
Details and comments