TY - BOOK

T1 - Motional quantum state engineering for quantum logic spectroscopy of molecular ions

AU - Wolf, Fabian

N1 - Doctoral thesis

PY - 2019

Y1 - 2019

N2 - High precision spectroscopy of molecular ions is a promising tool for the investigation of fundamental physics. Potential applications are the search for a possible variation of fundamental constants, the measurement of an electron electric dipole moment or the direct measurement of a frequency shift caused by parity violation in chiral molecules. The complex structure of molecules including the additional degrees of freedom, namely rotation and vibration, in general results in a dense level structure and the absence of closed cycling transitions. Consequently, techniques that have enabled high precision laser spectroscopy on atomic ions, such as direct laser cooling, optical pumping and fluorescence detection, are not applicable to most molecular ions. This obstacle can be overcome by employing quantum logic techniques to enable precision spectroscopy on molecules. For this purpose, the molecular ion is co-trapped with an atomic ion that has a suitable transition for laser cooling and state detection. The Coulomb repulsion couples the motional degrees of freedom of the ions. This coupling enables sympathetic cooling and information transfer from the molecule's internal state to the atomic qubit. In this cumulative thesis, the first experimental implementation of a quantum logic assisted scheme for reading out the internal state of a molecular ion is presented. In this scheme, the magnesium-25 ion is used to detect a state dependent force that acts on the molecular 24MgH+-ion. Furthermore, a quantum-enhanced force sensing protocol is demonstrated, which can be applied to the previously described molecule measurement, but has further applications in the more general field of quantum metrology. A salient feature of the presented quantum sensing protocol is that the metrological gain, achieved by employing the quantum features of the ion's motional state, is independent of the phase of the measured oscillating force. This is a substantial difference to previously demonstrated schemes based on squeezed states or Schrödinger cat states, and allows probing of two conjugate variables with sensitivities below the classical limit using the same initial quantum state.

AB - High precision spectroscopy of molecular ions is a promising tool for the investigation of fundamental physics. Potential applications are the search for a possible variation of fundamental constants, the measurement of an electron electric dipole moment or the direct measurement of a frequency shift caused by parity violation in chiral molecules. The complex structure of molecules including the additional degrees of freedom, namely rotation and vibration, in general results in a dense level structure and the absence of closed cycling transitions. Consequently, techniques that have enabled high precision laser spectroscopy on atomic ions, such as direct laser cooling, optical pumping and fluorescence detection, are not applicable to most molecular ions. This obstacle can be overcome by employing quantum logic techniques to enable precision spectroscopy on molecules. For this purpose, the molecular ion is co-trapped with an atomic ion that has a suitable transition for laser cooling and state detection. The Coulomb repulsion couples the motional degrees of freedom of the ions. This coupling enables sympathetic cooling and information transfer from the molecule's internal state to the atomic qubit. In this cumulative thesis, the first experimental implementation of a quantum logic assisted scheme for reading out the internal state of a molecular ion is presented. In this scheme, the magnesium-25 ion is used to detect a state dependent force that acts on the molecular 24MgH+-ion. Furthermore, a quantum-enhanced force sensing protocol is demonstrated, which can be applied to the previously described molecule measurement, but has further applications in the more general field of quantum metrology. A salient feature of the presented quantum sensing protocol is that the metrological gain, achieved by employing the quantum features of the ion's motional state, is independent of the phase of the measured oscillating force. This is a substantial difference to previously demonstrated schemes based on squeezed states or Schrödinger cat states, and allows probing of two conjugate variables with sensitivities below the classical limit using the same initial quantum state.

UR - https://kxp.k10plus.de/DB=2.1/CMD?MATCFILTER=N&MATCSET=N&ACT0=&IKT0=&TRM0=&ACT3=*&IKT3=8183&ACT=SRCHA&IKT=1016&SRT=YOP&TRM=Motional+quantum+state+engineering+for+quantum+logic+spectroscopy+of+molecular+ions&TRM3=

M3 - Doctoral thesis

T3 - PTB-Bericht

CY - Hannover

ER -