Exploring strongly correlated Rydberg excitations in cold gases using Full Counting Statistics

This Thesis aims to investigate the role of correlations arising in cold Rydberg samples as a consequence of the strong interactions between its constituents. For this purpose, two different approaches, which allow the study of different correlations, are presented here. On the one hand, as a consequence of the interactions between the excitations, resonantly excited Rydberg ensembles exhibit a strong degree of anti-correlation, which becomes visible either through the blockade of the excitation, or through a slowing down of the dynamics. On the other hand, the Rydberg-Rydberg interactions in the off-resonant regime enhance the generation of new excitations, leading the system to exhibit strong correlations. Moreover, by analyzing the full counting statistics (FCS) of the excitation events we get more insight into this process. Thus, in the off-resonant case, the most notable features of these strong correlations are the bimodal shapes of histograms of the counting distributions. Furthermore, under strong dissipative conditions, the FCS analysis reveals signs of a transition between two dynamical phases. Although the afore-mentioned effects were observed in a system governed by an Ising-type Hamiltonian, correlations emerge in other systems as well. For instance, in systems described by Heisenberg XX-type Hamiltonians, the strong interactions lead the dipolar energy exchange between the excitations

Seeded excitation avalanches in off-resonantly driven Rydberg gases

We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical models and numerical simulations of the excitation avalanches that agree well with our experimental results.Comment: 13 pages, 6 figure

Superconducting Resonator-Rydberg Atom Hybrid in the Strong Coupling Regime

We propose a promising hybrid quantum system, where a highly-excited atom strongly interacts with a superconducting LC oscillator via the electric field of capacitor. An external electrostatic field is applied to tune the energy spectrum of atom. The atomic qubit is implemented by two eigenstates near an avoided-level crossing in the DC Stark map of Rydberg atom. Varying the electrostatic field brings the atomic-qubit transition on- or off-resonance to the microwave resonator, leading to a strong atom-resonator coupling with an extremely large cooperativity. Like the nonlinearity induced by Josephson junctions in superconducting circuits, the large atom-resonator interface disturbs the harmonic potential of resonator, resulting in an artificial two-level particle. Different universal two-qubit logic gates can also be performed on our hybrid system within the space where an atomic qubit couples to a single photon with an interaction strength much larger than any relaxation rates, opening the door to the cavity-mediated state transmission.Comment: 4 figure

Van der Waals explosion of cold Rydberg clusters

We report on the direct measurement in real space of the effect of the van der Waals forces between individual Rydberg atoms on their external degrees of freedom. Clusters of Rydberg atoms with interparticle distances of around 5μm are created by first generating a small number of seed excitations in a magneto-optical trap, followed by off-resonant excitation that leads to a chain of facilitated excitation events. After a variable expansion time the Rydberg atoms are field ionized, and from the arrival time distributions the size of the Rydberg cluster after expansion is calculated. Our experimental results agree well with a numerical simulation of the van der Waals explosion

Exploring strongly correlated Rydberg excitations in cold gases using full counting statistics

This Thesis aims to investigate the role of correlations arising in cold Rydberg samples as a consequence of the strong interactions between its constituents. For this purpose, two different approaches, which allow the study of different types of correlations, are presented here. On the one hand, as a consequence of the interactions between the excitations, resonantly excited Rydberg ensembles exhibit a strong degree of anti-correlation, which becomes visible either through the blockade of the excitation, or through a slowing down of the dynamics. On the other hand, the Rydberg-Rydberg interactions in the off-resonant regime enhance the generation of new excitations, leading the system to exhibit strong correlations. Moreover, by analyzing the full counting statistics (FCS) of the excitation events we get more insight into this process. Thus, in the off-resonant case, the most notable features of these strong correlations are the bimodal shapes of histograms of the counting distributions. Furthermore, under strong dissipative conditions, the FCS analysis reveals signs of a transition between two dynamical phases. Although the afore-mentioned effects were observed in a system governed by an Ising-type Hamiltonian, correlations emerge in other systems as well. For instance, in systems described by Heisenberg XX-type Hamiltonians, the strong interactions lead the dipolar energy exchange between the excitations

Full counting distribution and phase diagram of a strongly interacting Rydberg gas

Atoms excited to high-lying quantum states, so-called Rydberg atoms, are highly polarizable and, therefore, interact strongly with each other even at large distances. One result of these interactions is the Rydberg dipole blockade effect, in which an excited atom may prevent other atoms from being excited by shifting them out of resonance. This blockade offers several applications, such as the realization of quantum logic gates [1] and the possibility of creating entangled states with two atoms [2]. Furthermore, the blockade mechanism constitutes the basis for the observation of many-body effects [3] involving long-range correlations and crystallization of Rydberg excitations [4

Van-der-Waals explosion of cold Rydberg aggregates

No abstract available

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved