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Fix Trotter evolution of sums with identity terms #1304
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Previously, Trotterization did not exclude any terms consisting of a scalar times the identity from the list of terms to be repeated. Instead, if present, an identity term was included in the resulting circuit as repeated identity gates, with the coefficient of the identity operator discarded. But, this coefficient must be accounted for: exp(-i * coeff * I) should introduce a global phase. With this PR, we remove the scalar-multiple-of-identity terms from the SummedOp to be Trotterized. We then set the global phase of the resulting circuit to account for the removed identity term. Fixes qiskit-community#1269
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…iskit-aqua#1304) * Fix Trotter evolution of sums with identity terms Previously, Trotterization did not exclude any terms consisting of a scalar times the identity from the list of terms to be repeated. Instead, if present, an identity term was included in the resulting circuit as repeated identity gates, with the coefficient of the identity operator discarded. But, this coefficient must be accounted for: exp(-i * coeff * I) should introduce a global phase. With this PR, we remove the scalar-multiple-of-identity terms from the SummedOp to be Trotterized. We then set the global phase of the resulting circuit to account for the removed identity term. Fixes qiskit-community/qiskit-aqua#1269 * Add test for Trotter evolution of sums with identity terms * Add release note for fix-trotter-global-phase * Fix linter complaints Co-authored-by: Steve Wood <40241007+woodsp-ibm@users.noreply.github.com>
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…iskit-aqua#1304) * Fix Trotter evolution of sums with identity terms Previously, Trotterization did not exclude any terms consisting of a scalar times the identity from the list of terms to be repeated. Instead, if present, an identity term was included in the resulting circuit as repeated identity gates, with the coefficient of the identity operator discarded. But, this coefficient must be accounted for: exp(-i * coeff * I) should introduce a global phase. With this PR, we remove the scalar-multiple-of-identity terms from the SummedOp to be Trotterized. We then set the global phase of the resulting circuit to account for the removed identity term. Fixes qiskit-community/qiskit-aqua#1269 * Add test for Trotter evolution of sums with identity terms * Add release note for fix-trotter-global-phase * Fix linter complaints Co-authored-by: Steve Wood <40241007+woodsp-ibm@users.noreply.github.com>
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…iskit-aqua#1304) * Fix Trotter evolution of sums with identity terms Previously, Trotterization did not exclude any terms consisting of a scalar times the identity from the list of terms to be repeated. Instead, if present, an identity term was included in the resulting circuit as repeated identity gates, with the coefficient of the identity operator discarded. But, this coefficient must be accounted for: exp(-i * coeff * I) should introduce a global phase. With this PR, we remove the scalar-multiple-of-identity terms from the SummedOp to be Trotterized. We then set the global phase of the resulting circuit to account for the removed identity term. Fixes qiskit-community/qiskit-aqua#1269 * Add test for Trotter evolution of sums with identity terms * Add release note for fix-trotter-global-phase * Fix linter complaints Co-authored-by: Steve Wood <40241007+woodsp-ibm@users.noreply.github.com>
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Previously, Trotterization did not exclude any terms consisting of a scalar times the
identity from the list of terms to be repeated. Instead, if present, an identity term was
included in the resulting circuit as repeated identity gates, with the coefficient of the
identity operator discarded. But, this coefficient must be accounted for:
exp(-i * coeff * I)should introduce a global phase.With this PR, we remove the scalar-multiple-of-identity terms from the SummedOp to be
Trotterized. We then set the global phase of the resulting circuit to account for the
removed identity terms.
Fixes #1269
This PR appears to solve the problem and not cause tests to fail.
It requires tests and a release note.