Photoassociation of Ultracold CsYb Molecules and Determination of Interspecies Scattering Lengths

This thesis reports the first measurements of the ground state binding energies of CsYb molecules and the scattering lengths of the Cs+Yb system. The knowledge gained from these measurements will be essential for devising the most efficient route for the creation of rovibrational ground state CsYb molecules. CsYb molecules in the rovibrational ground state possess both electric and magnetic dipole moments which opens up a wealth of applications in many areas of physics and chemistry. In addition, we present the setup of a crossed beam optical dipole trap and the investigation of precooling and loading of Yb into the dipole trap. Evaporative cooling in the dipole trap results in the reliable production of Bose-Einstein condensates with $4 \times 10^{5}$ $^{174}$Yb atoms. We also describe the necessary changes required to cool fermionic $^{173}$Yb atoms and report the production of a six-component degenerate Fermi gas of $8 \times 10^{4}$ $^{173}$Yb atoms with a temperature of 0.3~$T_{\rm F}$. As well as the ability to cool Yb to degeneracy, we present the production of Bose-Einstein condensates containing $5 \times 10^{4}$ $^{133}$Cs atoms. Effective cooling of Cs is achieved using Degenerate Raman sideband cooling, which enables $6 \times 10^{7}$ Cs atoms to be cooled to below $2 \, \mu$K and polarised in the $\ket{F=3, m_{F}=+3}$ state with 90~\% efficiency. Finally, we report the production of ultracold heteronuclear Cs$^*$Yb and CsYb molecules using one-photon and two-photon photoassociation respectively. For the electronically excited Cs$^*$Yb molecules we use trap-loss spectroscopy to detect molecular states below the Cs($^{2}P_{1/2}$) + Yb($^{1}S_{0}$) asymptote. For $^{133}$Cs$^{174}$Yb, we observe 13 rovibrational states with binding energies up to $\sim$500\,GHz. In addition, we produce ultracold fermionic $^{133}$Cs$^{173}$Yb and bosonic $^{133}$Cs$^{172}$Yb and $^{133}$Cs$^{170}$Yb molecules. From mass scaling, we determine the number of vibrational levels supported by the 2(1/2) excited-state potential to be 154 or 155

Learning and Memory in the Port Jackson Shark, Heterodontus portusjacksoni

Basic understanding of the fundamental principles and mechanisms involved in learning is lacking for elasmobranch fishes. Our aim in this study was to experimentally investigate the learning and memory capacity of juvenile Port Jackson sharks, Heterodontus portusjacksoni. Sharks (N = 30) were conditioned over a 19-day period to associate an underwater LED light or stream of air-bubbles [conditioned stimulus (CS)] with a food reward [unconditioned stimulus (US)], using three procedures (delay, trace and control). During experiments, the CS signalled at a random time between 180 and 300 s for 30 s (six times per day). For the delay the US overlapped in time with the CS, for the trace the US delivered 10 s after the CS and for our control the US was delivered at random time between 180 and 300 s after the CS. H. portusjacksoni sharks trained in all procedures improved consistently in their time to obtain food, indicative of Pavlovian learning. Importantly, the number of sharks in the feeding area 5 s prior to CS onset did not change over time for any procedures. However, significantly more sharks were present 5 s after CS onset for delay for both air-bubble and light CS. Sharks trained in the delay and trace procedures using air-bubbles as the CS also displayed significantly more anticipatory behaviours, such as turning towards the CS and biting. Sharks trained with the light CS did not exhibit such behaviours; however, trace procedural sharks did show a significant improvement in moving towards the CS at its onset. At 20 and 40 days after the end of the conditioning experiments, some sharks were presented the CS without reward. Two sharks trained in the delay procedure using air-bubbles as the CS exhibited biting behaviours: one at 20 and the other at 40 days. This study demonstrates that H. portusjacksoni have the capacity to learn a classical conditioning procedure relatively quickly (30 trials during 5 days) and associate two time-separated events and retention of learnt associations for at least 24 h and possibly up to 40 days

Observation of Rydberg Blockade Due to the Charge-Dipole Interaction between an Atom and a Polar Molecule

We demonstrate Rydberg blockade due to the charge-dipole interaction between a single Rb atom and a single RbCs molecule confined in optical tweezers. The molecule is formed by magnetoassociation of a Rb þ Cs atom pair and subsequently transferred to the rovibrational ground state with an efficiency of 91(1)%. Species-specific tweezers are used to control the separation between the atom and molecule. The charge-dipole interaction causes blockade of the transition to the Rb(52s) Rydberg state, when the atommolecule separation is set to 310(40) nm. The observed excitation dynamics are in good agreement with simulations using calculated interaction potentials. Our results open up the prospect of a hybrid platform where quantum information is transferred between individually trapped molecules using Rydberg atomsJunta de Andalucia A-FQM-52-UGR20UK Research & Innovation (UKRI) Engineering & Physical Sciences Research Council (EPSRC) EP/P01058X/1 EP/V047302/1 EP/W00299X/1UK Research and Innovation (UKRI) Frontier Research EP/X023354/1Royal SocietyDurham UniversityMICIN PID2020-113390 GB-I00Junta de Andalucia PY20-00082ERDF-University of Granada A-FQM-52-UGR20Andalusian Research Group FQM-207National Science Foundation (NSF