Adding the feature of calculating entanglement measures negativity

[pranay1990]

I and @PayalSolanki2906 are adding the feature which can be used to calculate the entanglement measures negativity and logarithmic negativity. To this end, we have created a function: negativity inside qiskit.quantum_info.states.measures module.

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[coveralls]

Pull Request Test Coverage Report for Build 5123431309

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• 211 unchanged lines in 27 files lost coverage.
• Overall coverage decreased (-0.02%) to 85.915%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/transpiler/passes/routing/commuting_2q_gate_routing/commuting_2q_block.py	1	95.65%
qiskit/transpiler/passes/routing/commuting_2q_gate_routing/commuting_2q_gate_router.py	1	99.07%
qiskit/transpiler/passes/synthesis/unitary_synthesis.py	1	90.27%
qiskit/transpiler/synthesis/aqc/cnot_unit_objective.py	1	99.26%
crates/accelerate/src/results/marginalization.rs	2	91.57%
crates/qasm2/src/lex.rs	2	91.9%
qiskit/circuit/add_control.py	2	96.3%
qiskit/dagcircuit/collect_blocks.py	2	98.6%
qiskit/extensions/quantum_initializer/squ.py	2	80.0%
qiskit/transpiler/passes/layout/disjoint_utils.py	3	97.48%

Totals
Change from base Build 5030016914:	-0.02%
Covered Lines:	71159
Relevant Lines:	82825

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💛 - Coveralls

[ikkoham]

Thank you. It looks almost good to me.

[pranay1990]

Hi @ikkoham, we have made the necessary changes to the code. Thank you for the insightful comments. Please let us know if any further changes are required.

[diemilio]

Hi @pranay1990 and @PayalSolanki2906. One suggestion on using numpy.linalg.svd. If you only need the singular values, you can set the compute_uv param to False to avoid computing the u and vh matrices. Makes the code cleaner and perhaps a bit more efficient.

[ikkoham]

Thanks a lot. Now the codes are simple and looks good to me. compute_uv=False is also nice to reduce the computational cost. Great!