Abstract
A general method for rotational microwave spectroscopy and control of polar molecular ions via direct microwave addressing is considered. Our method makes use of spatially varying ac Stark shifts, induced by far off-resonant, focused laser beams to achieve an effective coupling between the rotational state of a molecular ion and the electronic state of an atomic ion. In this setting, the atomic ion is used for read-out of the molecular ion state, in a manner analogous to quantum logic spectroscopy based on Raman transitions. In addition to high-precision spectroscopy, this setting allows for rotational ground state cooling, and can be considered as a candidate for the quantum information processing with polar molecular ions. All elements of our proposal can be realized with currently available technology.
Highlights
Precise measurement and control of molecular quantum states are essential to the advancement of a wide range of scientific fields
Building on the early work on quantum logic spectroscopy (QLS), we propose a scheme that allows high-precision spectroscopy and ground state initialization of rotational states in molecular ions using microwave fields
A key element of the QLS protocol described in the previous section is the mapping of the rotational state onto the common motional state of both ions via a sideband transition driven by the spectroscopy field (step (iii))
Summary
Precise measurement and control of molecular quantum states are essential to the advancement of a wide range of scientific fields. Building on the early work on QLS, we propose a scheme that allows high-precision spectroscopy and ground state initialization of rotational states in molecular ions using microwave fields. One challenge to address the molecular rotational state transitions with microwave fields is that the long wave length implies that the mapping of the rotational state to the ion’s electronic state via the motional bus [28] is in general too weak for any practical implementation We show that this coupling can be dramatically enhanced via the interaction with a far off-resonant optical field, in a scheme analogous to the methods used for atomic ions in magnetic field gradients [29, 30].
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