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The effect of data encoding on the expressive power of variational quantum machine learning models

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arxiv 2008.08605 v2 pith:H7P7NTWQ submitted 2020-08-19 quant-ph stat.ML

classification quant-phstat.ML
keywords quantumdatamodelsencodingaccessibleapproximatorscircuitsexpressive
verification ladder T0 review T1 audit T2 compute T3 formal
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Quantum computers can be used for supervised learning by treating parametrised quantum circuits as models that map data inputs to predictions. While a lot of work has been done to investigate practical implications of this approach, many important theoretical properties of these models remain unknown. Here we investigate how the strategy with which data is encoded into the model influences the expressive power of parametrised quantum circuits as function approximators. We show that one can naturally write a quantum model as a partial Fourier series in the data, where the accessible frequencies are determined by the nature of the data encoding gates in the circuit. By repeating simple data encoding gates multiple times, quantum models can access increasingly rich frequency spectra. We show that there exist quantum models which can realise all possible sets of Fourier coefficients, and therefore, if the accessible frequency spectrum is asymptotically rich enough, such models are universal function approximators.

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Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. OpenAlex reports about 575 citations worldwide. Full citation record

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