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Unitary transformations using robust optimal control on a cold atom qudit

E. Flament1, N. Ombredane1, F. Arrouas1, D. Ronco1, B. Peaudecerf1, D. Sugny2, and D. Guéry-Odelin1

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Phys. Rev. Research 7, 033069 – Published 16 July, 2025

DOI: https://doi.org/10.1103/fvlj-yph6

Abstract

In this paper, we design and experimentally implement various robust quantum unitary transformations (gates) acting on d-dimensional vectors (qudits) by tuning a single control parameter using optimal control theory. The quantum state is represented by the momentum components of a Bose-Einstein condensate placed in an optical lattice, with the lattice position varying over a fixed duration serving as the control parameter. To evaluate the quality of these transformations, we employ standard quantum process tomography. In addition, we show how controlled unitary transformations can be used to extend state stabilization to global stabilization within a controlled vector subspace. Finally, we apply them to state tomography, showing how the information about the relative phase between distant momentum components can be extracted by inducing an interference process.

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Phys. Rev. Research 7, 033069– Published 16 July, 2025
  • Received 12 March 2025
  • Accepted 12 May 2025
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