Trapped Ion Quantum Information Group

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Molecules

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Figure 1: Our ion trap is made from a single piece of glass with deposited gold forming the trap electrodes. The glass structure is 8.5 mm long. The lower inset shows a fluorescence image of a single trapped Be+ ion. The co-trapped H2+ ion is invisible, but its presence can be inferred from the position and mechanical resonances of the Be+ ion. The upper inset shows a quantum logic signal, making the H2+ visible.

The complexity and variety of molecular systems promise a wide range of applications: high-​​precision spectroscopy to search for parity violations not covered by the Standard Model of particle physics, measurement of fundamental constants and their possible variation with time, high-precision tests of quantum electrodynamics, molecule-​​based optical clocks, and quantum information processing using molecular degrees of freedom. These applications either require or benefit from state preparation and non-​​destructive measurements. Unfortunately, these tools are hard to implement even for selected molecular species.

As has recently been demonstrated, quantum-​​logic spectroscopy can provide full control over a single molecular ion by co-​trapping it with a well-​​controlled atomic "logic" ion [1,2,3]. In principle, this technique can provide control over any molecular ​​ion species, resulting in tremendous potential for research and applications of molecular ions in the quantum regime.

We aim to perform quantum-​​logic spectroscopy of the hydrogen molecular ion by co-​trapping it with a beryllium atomic ion. The hydrogen molecular ion is the simplest molecule and therefore serves as an important standard to test molecular theory, just as the hydrogen atom does for atomic physics. With our research, we hope to contribute to molecular models and to measurements of fundamental constants such as the electron-proton mass ratio.

Using the trap fabrication technique developed in the TIQI group, we have built a monolithic four-​rod trap specifically designed for high-​precision spectroscopy. To prevent ion loss due to chemical reactions, the trap is located in a cryogenic vacuum chamber at about 10 K. This allows us to trap and cool Be+/H2+ ion pairs with lifetimes of up to 11 h [4]. Figure 1 shows our trap and our first quantum logic signal.

Current Team Members
David Holzapfel, Dr. Fabian Schmid

The project is independently led by Dr. Daniel Kienzler ().

[1] P. O. Schmidt et al., Science 309, 749-​​752 (2005)
[2] F. Wolf et al., Nature 530, 457-​​460 (2016)
[3] C.-W. Chou et al., Nature, 545, 203-​​207 (2017)
[4] N. Schwegler et al., Phys. Rev. Lett. 131, 133003 (2023)

 

 

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