124 lines
4.2 KiB
Plaintext
124 lines
4.2 KiB
Plaintext
---
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title: GraphDecoder
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description: API reference for qiskit.ignis.verification.GraphDecoder
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.ignis.verification.GraphDecoder
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---
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# GraphDecoder
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<Class id="qiskit.ignis.verification.GraphDecoder" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-ignis/tree/stable/0.6/qiskit/ignis/verification/topological_codes/fitters.py" signature="GraphDecoder(code, S=None)" modifiers="class">
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Bases: `object`
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Class to construct the graph corresponding to the possible syndromes of a quantum error correction code, and then run suitable decoders.
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**Parameters**
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* **code** (*RepitionCode*) – The QEC Code object for which this decoder will be used.
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* **S** (*retworkx.PyGraph*) – Graph describing connectivity between syndrome elements. Will be generated automatically if not supplied.
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**Additional information:**
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The decoder for the supplied `code` is initialized by running `_make_syndrome_graph()`. Since this process can take some time, it is also possible to load in a premade `S`. However, if this was created for a differently defined `code`, it won’t work properly.
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## Methods
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### get\_error\_probs
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<Function id="qiskit.ignis.verification.GraphDecoder.get_error_probs" signature="GraphDecoder.get_error_probs(results)">
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Generate probabilities of single error events from result counts.
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**Parameters**
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* **results** (*dict*) – A results dictionary, as produced by the
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* **method of the code.** (*process\_results*) –
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**Returns**
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Keys are the edges for specific error events, and values are the calculated probabilities
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**Return type**
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dict
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#### Additional information:
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Uses results to estimate the probability of the errors that create the pairs of nodes specified by the edge. Calculation done using the method of Spitz, et al. [https://doi.org/10.1002/qute.201800012](https://doi.org/10.1002/qute.201800012)
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</Function>
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### get\_logical\_prob
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<Function id="qiskit.ignis.verification.GraphDecoder.get_logical_prob" signature="GraphDecoder.get_logical_prob(results, algorithm='matching')">
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**Parameters**
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* **results** (*dict*) – A results dictionary, as produced by the
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* **method of the code.** (*process\_results*) –
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* **algorithm** (*str*) – Choice of which decoder to use.
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**Returns**
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Dictionary of logical error probabilities for each of the encoded logical states whose results were given in the input.
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**Return type**
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dict
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</Function>
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### make\_error\_graph
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<Function id="qiskit.ignis.verification.GraphDecoder.make_error_graph" signature="GraphDecoder.make_error_graph(string, subgraphs=None)">
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**Parameters**
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* **string** (*str*) – A string describing the output from the code.
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* **subgraphs** (*list*) – Used when multiple, semi-independent graphs need
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* **to created.** (*need*) –
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**Returns**
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The subgraph(s) of S which corresponds to the non-trivial syndrome elements in the given string.
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**Return type**
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E
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</Function>
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### matching
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<Function id="qiskit.ignis.verification.GraphDecoder.matching" signature="GraphDecoder.matching(string)">
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**Parameters**
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**string** (*str*) – A string describing the output from the code.
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**Returns**
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**A string with corrected logical values,**
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computed using minimum weight perfect matching.
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**Return type**
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str
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#### Additional information:
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This function can be run directly, or used indirectly to calculate a logical error probability with get\_logical\_prob
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</Function>
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### weight\_syndrome\_graph
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<Function id="qiskit.ignis.verification.GraphDecoder.weight_syndrome_graph" signature="GraphDecoder.weight_syndrome_graph(results)">
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Generate weighted syndrome graph from result counts.
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**Parameters**
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* **results** (*dict*) – A results dictionary, as produced by the
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* **method of the code.** (*process\_results*) –
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#### Additional information:
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Uses results to estimate the probability of the errors that create the pairs of nodes in S. The edge weights are then replaced with the corresponding -log(p/(1-p).
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</Function>
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</Class>
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