Department of Physics & Astronomy
University of New Mexico

CQuIC Seminars

Quantum Logic Control of a Single Molecular Ion

Presented by Dietrich Leibfried (NIST)

An amazing level of quantum control is routinely reached in modern experiments with atoms, but similar control over molecules has been an elusive goal. A method based on quantum logic spectroscopy [1] can address this challenge for a wide class of molecular ions [2,3]. We have now realized the basic elements of this proposal. In our demonstration, we trap a calcium ion together with a calcium hydride ion (CaH + ) that is a convenient stand-in for more general molecular ions. We laser-cool the two-ion crystal to its motional ground state and then drive Raman-transitions in the molecular ion, where a transition in the molecule also deposits a single quantum of excitation in the motion of the ion pair (motional 'sidebands'). We can efficiently detect this single quantum of excitation with the calcium ion, which projects the molecule into the final state of the sideband transition, a known, pure quantum state. The molecule can be coherently manipulated after the projection, and its resulting state read out by another quantum logic state detection. We demonstrate this by driving Rabi oscillations between different rotational states [4, 5] and by entangling the molecular ion with the logic ion [6]. All transitions in the molecule are either driven by a single, far off-resonant continuous-wave laser or by a far-off-resonant frequency comb. This allows us to demonstrate quantum control and precision measurements using an apparatus that admits access to a much larger class of molecular ions.
[1] P.O. Schmidt, et al. Science 309, 749 (2005).
[2] S. Ding, S. and D. N. Matsukevich, New J. Phys. 14, 023028 (2012).
[3] D. Leibfried, New J. Phys. 14, 023029 (2012).
[4] C.-W. Chou et al., Nature 545, 203 (2017).
[5] C.-W. Chou et al., Science 367, 1458 (2020).
[6] Y. Lin et al., Nature 581, 273 (2020).

3:30 pm, Thursday, September 30, 2021

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