Data re-uploading for a universal quantum classifier, Maria Schuld, Gavin E. Crooks, Ioana Niculescu, Kyle Bradlow, and Nathan Killoran, 2021npj Quantum Information, Vol. 7 (Nature Publishing Group)DOI: 10.1038/s41534-021-00406-z - Introduces the data re-uploading technique, a method that uses multiple layers of data-dependent gates in a quantum circuit to create rich feature maps with a fixed, potentially small, number of qubits, addressing the challenge of high-dimensional encoding.
Supervised learning with quantum-enhanced feature spaces, Vojtěch Havlíček, Antonio D. Córcoles, Kristan Temme, Aram W. Harrow, Abhinav Kandala, Jerry M. Chow, and Jay M. Gambetta, 2019Nature, Vol. 567DOI: 10.1038/s41586-019-0980-2 - A highly influential paper demonstrating how classical data can be mapped to quantum feature spaces for supervised learning tasks, particularly relevant to quantum kernel methods and implicit amplitude-like encodings for high-dimensional data.