41 lines
1.3 KiB
Plaintext
41 lines
1.3 KiB
Plaintext
---
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title: mutual_information
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description: API reference for qiskit.quantum_info.mutual_information
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in_page_toc_min_heading_level: 1
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python_api_type: function
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python_api_name: qiskit.quantum_info.mutual_information
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---
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# qiskit.quantum\_info.mutual\_information
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<Function id="qiskit.quantum_info.mutual_information" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.20/qiskit/quantum_info/states/measures.py" signature="mutual_information(state, base=2)">
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Calculate the mutual information of a bipartite state.
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The mutual information $I$ is given by:
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$$
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I(\rho_{AB}) = S(\rho_A) + S(\rho_B) - S(\rho_{AB})
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$$
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where $\rho_A=Tr_B[\rho_{AB}], \rho_B=Tr_A[\rho_{AB}]$, are the reduced density matrices of the bipartite state $\rho_{AB}$.
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**Parameters**
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* **state** ([*Statevector*](qiskit.quantum_info.Statevector "qiskit.quantum_info.Statevector") *or*[*DensityMatrix*](qiskit.quantum_info.DensityMatrix "qiskit.quantum_info.DensityMatrix")) – a bipartite state.
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* **base** (*int*) – the base of the logarithm \[Default: 2].
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**Returns**
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The mutual information $I(\rho_{AB})$.
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**Return type**
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float
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**Raises**
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* **QiskitError** – if the input state is not a valid QuantumState.
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* **QiskitError** – if input is not a bipartite QuantumState.
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</Function>
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