Interferometry using magnetic sensitive states

Saeed Hamzeloui

Atomic interferometry is a very sensitive technique in precision measurements. In this PhD work we explore ways to improve certain aspects of atomic interfer- ometry. We show that there are some advantages on using magnetic sensitive states. We introduce the required infrastructures to implement Ramsey type interferometry on particular transitions. Using a Magneto Optical Trap (MOT) which is the main prerequisite, the atoms are trapped and cooled. The trapping procedure with the MOT requires ingredients such as lasers, the homogeneous and inhomogeneous magnetic fields, the chamber containing the sample, the vacuum system and the detection part (see Chapter 2). At the beginning of my PhD, this facility for trapping the rubidium atoms was available. Later on we upgraded the vacuum system. During this PhD work we could further cool down the trapped sample thanks to the optical molasses technique. We maintain the atoms at temperatures typically below some tenths of micro Kelvin. The coherent manipulation of the atoms is the significant part of this thesis since we aim to do atomic interferometry. Using radiations in microwave domain, it is feasible to couple any two states and do the Rabi oscillations between the hyperfine and Zeeman levels.\nMy first work as a PhD student was to contribute in the Dual Isotope MOT (DIMOT) experiment (see Chapter 3). The idea was to trap both isotopes of rubidium simultaneously by using only single laser and an Electro-Optical Modulator (EOM). This work introduces huge simplifications on the optical part and is extendable to trap more isotopes at the same time. The experiment has the optical and RF parts and my contribution was to complete the RF part.\nStarting all the atoms at the particular initial point for the interferometry takes us some considerable time to be sure that we correctly transfer the atomic population into the desired state (see the discussion in Chapter 4). From that point we focused on two transitions to use the Ramsey type interferometer. Each of these two transitions have an optimum operating point in order to be far from the magnetic field fluctuations since the interferometers are quite sensitive to the field perturbations sensed from the environment. At the end we aim to combine these two transitions of interest to make a dual interferometer (see Chapter 6). The idea is to obtain the minimum magnetic sensitivity at a tunable magnetic field by changing the fraction of atoms in each interferometer. The dual interferometer may be useful in applications where low magnetic sensitivity is required at a particular magnetic field.

F. De Martini, G. Denardo, Anton Zeilinger

Y. Q. Chai, M. Zhang, L. F. Wei

Sensitive detection of magnetic field is one of the open problem in metrology. Here, we propose an Mach-Zehnder atomic interferometry to sensitively detect the very weak local magnetic field, which is expelled by the superconductor (as the "testing magnet") due to the Meissner effect. The induced magnetic field gradient near the superconductor provides a centripetal acceleration of the atomic motion in the interferometry and thus can be detected by using the atomic interferences. Given gravity acceleration of the atoms have been measured at the accuracy of $10^{-12}$ g, the measured sensitivity of the expelled local field could reach $10^{-14}$ T.

R. Wynand, Sven Brandt, A. Nagel +1 more

Ángel S. Sanz, Salvador Miret-Artés

Jon P. Davis, Frank A. Narducci

We propose the utilization of atom interferometry techniques for the measurement of magnetic fields in noisy environments. We find that the interferometer we propose is insensitive (to first order) to the magnetic field but is sensitive to the field gradient. We propose a technique by which a superposition of magnetically sensitive states (a beam splitter) can be achieved. We experimentally demonstrate our techniques to null the magnetic field at the location of a cold atom cloud and how we can probe the population of magnetic sublevels.