Coherent atom-light interactions in multi-level systems

This thesis presents work on experiments performed using electromagnetically induced transparency (EIT) in Rubidium vapour cells. Starting with a simple three-level Λ-system, extra complexity is introduced by adding an additional control beam. This makes the switching from narrow transmitting resonances to absorbing resonances possible. Rydberg EIT is then introduced and is used to shown how the switching of such resonances using external electric fields in possible. The work then progresses towards the use of thin vapour cells to overcome the limitations of conventional systems. In the transition to thin vapour cells, the role of dipole interactions in Rydberg atoms motivates the idea of an atomic quantum dot. The Kerr effect is then characterised and used to perform phase modulation in a gas. The Rydberg state itself is then phase modulated and this is shown to give rise to frequency sidebands which offer a promising way of determining dc electric fields

Virtual learning environment for interactive engagement with advanced quantum mechanics

A virtual learning environment can engage university students in the learning process in ways that the traditional lectures and lab formats can not. We present our virtual learning environment \emph{StudentResearcher} which incorporates simulations, multiple-choice quizzes, video lectures and gamification into a learning path for quantum mechanics at the advanced university level. \emph{StudentResearcher} is built upon the experiences gathered from workshops with the citizen science game Quantum Moves at the high-school and university level, where the games were used extensively to illustrate the basic concepts of quantum mechanics. The first test of this new virtual learning environment was a 2014 course in advanced quantum mechanics at Aarhus University with 47 enrolled students. We found increased learning for the students who were more active on the platform independent of their previous performances.Comment: 8 pages, 6 figure

Dispersive detection of radio-frequency-dressed states

We introduce amethod to dispersively detect alkali-metal atoms in radio-frequency-dressed states. In particular, we use dressed detection tomeasure populations and population differences of atoms prepared in their clock states. Linear birefringence of the atomic medium enables atom number detection via polarization homodyning, a form of common path interferometry. In order to achieve low technical noise levels, we perform optical sideband detection after adiabatic transformation of bare states into dressed states. The balanced homodyne signal then oscillates independently of field fluctuations at twice the dressing frequency, thus allowing for robust, phase-locked detection that circumvents low-frequency noise. Using probe pulses of two optical frequencies, we can detect both clock states simultaneously and obtain population difference as well as the total atom number. The scheme also allows for difference measurements by direct subtraction of the homodyne signals at the balanced detector, which should technically enable quantum noise limited measurements with prospects for the preparation of spin squeezed states. The method extends to other Zeeman sublevels and can be employed in a range of atomic clock schemes, atom interferometers, and other experiments using dressed atoms

Spatially-selective in situ magnetometry of ultracold atomic clouds

We demonstrate novel implementations of high-precision optical magnetometers which allow for spatially-selective and spatially-resolved in situ measurements using cold atomic clouds. These are realised by using shaped dispersive probe beams combined with spatially-resolved balanced homodyne detection. Two magnetometer sequences are discussed: a vectorial magnetometer, which yields sensitivities two orders of magnitude better compared to a previous realisation and a Larmor magnetometer capable of measuring absolute magnetic fields. We characterise the dependence of single-shot precision on the size of the analysed region for the vectorial magnetometer and provide a lower bound for the measurement precision of magnetic field gradients for the Larmor magnetometer. Finally, we give an outlook on how dynamic trapping potentials combined with selective probing can be used to realise enhanced quantum simulations in quantum gas microscopes

Tailoring magnetic fields in inaccessible regions

Controlling magnetism, essential for a wide range of technologies, is impaired by the impossibility of generating a maximum of magnetic field in free space. Here, we propose a strategy based on negative permeability to overcome this stringent limitation. We experimentally demonstrate that an active magnetic metamaterial can emulate the field of a straight current wire at a distance. Our strategy leads to an unprecedented focusing of magnetic fields in empty space and enables the remote cancellation of magnetic sources, opening an avenue for manipulating magnetic fields in inaccessible regions