Workshop 2025: Protocols to measure the non-Abelian Berry phase by pumping a spin qubit through a quantum-dot loop

Session Information

Location: Lecture room F3213 - 11
Day: Wednesday, 14 May
Time: 18:00 - 19:00
Chairperson: -

Presentation Details

Presentation Type: Poster presentation
Title: Protocols to measure the non-Abelian Berry phase by pumping a spin qubit through a quantum-dot loop
Abstract: A quantum system constrained to a degenerate energy eigenspace can undergo a nontrivial time evolution upon adiabatic driving, described by a non-Abelian Berry phase. This type of dynamics may provide logical gates in quantum computing that are robust against timing errors. A strong candidate to realize such holonomic quantum gates is an electron or hole spin qubit trapped in a spin-orbit-coupled semiconductor, whose twofold Kramers degeneracy is protected by time-reversal symmetry.
In this work, we propose and quantitatively analyze a protocol to experimentally characterize the holonomic single-qubit gates induced by the non-Abelian Berry phase when a spin qubit is shuttled around a loop of quantum dots. The device, shown in the figure, includes an on-chip wire and a reservoir besides the loop. These ingredients are used for initialization and read out.
In semiconductor spin-qubit devices with strong spin-orbit interaction, e.g. planar SiGe/Ge quantum dot arrays, every loop induces a unitary transformation upon shuttling a spin qubit through it. This technique is suitable for realizing a universal single qubit holonomic gate set on a device with multiple quantum dot loops.
We also present extensions of the original protocol: a) a version characterizing the local internal Zeeman field directions in the dots, b) a simplified protocol offering the near-term measurement of the non-Abelian Berry phase.
We expect the protocols to be realized in the near future, as all key elements have been already demonstrated in spin-qubit experiments. The strong spin-orbit interaction and weak hyperfine interaction of holes in Si or Ge quantum wells make these materials strong candidates to observe these effects; the recently realized 3-4-3 Ge quantum dot array is especially promising due to its high material quality and the two-dimensional layout that enables shuttling a qubit through a loop.

Presenter

Mr Baksa Kolok
Budapest University of Technology and Economics | Hungary

Authors

1. Kolok, Baksa | Budapest University of Technology and Economics, H-1111 Budapest, Hungary
2. Pályi, András | Budapest University of Technology and Economics, H-1111 Budapest, Hungary