Jul 17 – 22, 2022
Royal Conservatory of Music, Toronto
America/Toronto timezone

Towards quantum control and spectroscopy of a single hydrogen molecular ion

Jul 21, 2022, 5:00 PM
1h 30m
Hart House (Hart House)

Hart House

Hart House

7 Hart House Cir, Toronto, ON M5S 3H3
Poster presentation Trapped ions, Rydberg atoms, and cold plasmas Poster session


The complexity and variety of molecules offer opportunities for metrology and quantum information that go beyond what is possible with atomic systems. The hydrogen molecular ion is the simplest of all molecules and can thus be calculated ab initio to very high precision [1]. In combination with spectroscopy this allows to determine fundamental constants and test fundamental theory at record precision [2–4]. Spectroscopy of the hydrogen molecular ion should improve substantially by performing experiments with single hydrogen molecular ions, reducing systematic uncertainties and improving signal strength. This necessitates quantum control.
I will present our progress towards full quantum control of a single hydrogen molecular ion. Our most recent results demonstrate the co-trapping of single H$_2^+$ and $^9$Be$^+$ ions. We observe H$_2^+$ trapping lifetimes of $\approx 10 \mathrm{h}$. We perform ground-state cooling of the ion pair’s axial in-phase mode of motion, resulting in an average phonon number of 0.088(4), which corresponds to a temperature of 24.8(4) μK.
The experimental apparatus features a cryogenic ultra-high vacuum chamber, housing a microfabricated monolithic linear Paul trap. H$_2^+$ is loaded into the trap by electron bombardment of H$_2$. We aim to use He buffer gas cooling in combination with quantum logic spectroscopy to initialize the internal state of H$_2^+$ in a pure quantum state and implement non-destructive readout [5, 6].

[1] V. I. Korobov, J.-P. Karr, M. Haidar, and Z.-X. Zhong, “Hyperfine structure in the H$_2^+$ and HD$^+$ molecular ions at order mα$^6$,”
Phys. Rev. A, vol. 102, p. 022804, Aug 2020.

[2] S. Alighanbari, G. S. Giri, F. L. Constantin, V. I. Korobov, and S. Schiller, “Precise test of quantum electrodynamics and determination of fundamental constants with HD$^+$ ions,”
Nature, vol. 581, no. 7807, pp. 152–158, 2020.

[3] S. Patra, M. Germann, J.-P. Karr, M. Haidar, L. Hilico, V. I. Korobov, F. M. J. Cozijn, K. S. E. Eikema, W. Ubachs, and J. C. J. Koelemeij, “Proton-electron mass ratio from laser spectroscopy of HD$^+$ at the part-per-trillion level,”
Science, vol. 369, no. 6508, pp. 1238–1241, 2020.

[4] I. V. Kortunov, S. Alighanbari, M. G. Hansen, G. S. Giri, V. I. Korobov, and
S. Schiller, “Proton–electron mass ratio by high-resolution optical spectroscopy of ion ensembles in the resolved-carrier regime,”
Nature Physics, vol. 17, pp. 569–573, 2021.

[5] S. Schiller, I. Kortunov, M. Hernández Vera, F. Gianturco, and H. da Silva,
“Quantum state preparation of homonuclear molecular ions enabled via a cold buffer gas: An ab initio study for the H$_2^+$ and the D$_2^+$ case,”
Phys. Rev. A, vol. 95, p. 043411, 2017.

[6] P. O. Schmidt, T. Rosenband, C. Langer, W. M. Itano, J. C. Bergquist, and D. J. Wineland, “Spectroscopy using quantum logic,”
Science, vol. 309, pp. 749–752, 2005.

Presenter name David Holzapfel
How will you attend ICAP-27? I am planning on in-person attendance

Primary authors

David Holzapfel (ETH Zürich) Nick Schwegler (ETH Zürich) Prof. Jonathan Home (ETH Zürich) Dr Daniel Kienzler (ETH Zürich)

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