Advancing the frontiers of quantum science and engineering

Abstract: This thesis reports on my experimental and theoretical work on ultracold 6Li40K molecules. It focuses on the investigation of their molecular spectra and on the coherent control of ground-state molecules within their rotational manifolds. These bosonic molecules possess a large permanent electric dipole moment of 3.6 D, which makes them a promising platform for quantum information processing, quantum simulation of novel dipolar many-body physics, ultracold chemistry, and precision measurements of fundamental constants. The primary goal of this work is to identify a two-photon pathway for coherently transferring weakly bound 6Li40K Feshbach molecules to their rovibrational ground state, thereby enabling the creation of a dipolar quantum gas. Two ex-cited molecular states with strong couplings to both the singlet Feshbach state and the absolute ground state are identified. This transfer pathway is experimentally demonstrated using coherent Raman transfer and stimulated Raman adiabatic passage (STIRAP). A one-way STIRAP efficiency of 96 ± 4% is achieved. Suppression of fast phase noise in the Raman laser system is identified as a key factor enabling this high transfer efficiency. Coherent control of the internal molecular degrees of freedom is further extended to the rotational states using microwave radiation. High resolution microwave spectroscopy resolves the hyperfine structure of the J = 1 rotational manifold, and several rotational parameters are extracted and found to be in good agreement with theoretical predictions. Coherent rotational control of 6Li40K molecules is demonstrated in time-of-flight measurements. In an optical dipole trap, however, differential AC Stark shifts lead to rapid decoherence of the rotational dynamics. In addition, chemical reactions and light-assisted sticky collisions limit the lifetime of ground-state molecules to approximately 5 ms. To suppress collisional losses, fermionic 6Li and 40K atoms are first loaded into a three-dimensional optical lattice. Lattice calibration is performed using observations of the superfluid-to–Mott-insulator transition, Kapitza–Dirac scattering, and Brillouin zone mapping. Confinement-induced formation of 6Li40K molecules is observed near an extended broad Feshbach resonance. To mitigate the detrimental effects of differential AC Stark shifts, the search for magic wavelengths is explored through measurements of molecular polarizabilities and AC Stark shifts. Spectroscopy near the |b3Π0, v = 0⟩ excited state is performed.  A narrow-linewidth transition is theoretically identified and experimentally observed. The differential polarizability between the ground and first rotationally excited states of 6Li40K molecules is investigated in the vicinity of this transition, and several usable magic points are identified. At these magic wavelengths, significantly extended rotational coherence times can be achieved. In conclusion, this thesis establishes key experimental capabilities for the pro-duction, coherent control, and magic trapping of ultracold ground-state 6Li40K molecules in three-dimensional optical lattices. These results lay the groundwork for future studies of dipolar many-body physics and for applications in quantum simulation, quantum computation, and quantum information processing.

Abstract: As quantum technologies increase in scale and complexity, new challenges arise in understanding and controlling large-scale quantum systems. Fundamental questions remain about the nature of quantum information, quantum-classical correspondence, and the connection between chaos theory and quantum mechanics. This talk will provide an overview of our recent studies of quantum chaos and quantum information processing, including the first simulations of chaos on a programmable quantum computer, and the identification of new quantum periodicities that have no classical analog.

Abstract: Discrete-event simulation (DES) engines like NetSquid are essential tools for designing and optimizing quantum communication networks, allowing protocol feasibility studies and requirement assessments without expensive hardware deployment. However, as network scale and physical parameter set grow, these simulators hit hard computational limits. Here, we introduce NetSquid's design and show how it bridges device-level parameters to network-level protocol metrics using a comparison of BB84 and MDI-QKD as a running example. We demonstrate what makes it powerful - and confront its fundamental scaling bottleneck. A modest parameter sweep over a physically realistic metropolitan network of 100 nodes on a modern high-end consumer device can require full CPU utilisation for periods of the order of one week or more. This is a scaling issue core to any DES engine. Quantum memories, entanglement swapping and other quantum-native effects introduce more complex interdependencies resistant to parallelisation. We close by posing the open question of what this means for the trajectory of quantum network modelling: whether to optimise existing DES frameworks, or to design bespoke for specific network architectures as the field reaches application scale.

The Quantum Information Processing Conference (QIP) is the largest quantum information processing technology conference, which annually gathers the world’s brightest researchers and industry leaders for a week long program to present and discuss the latest achievements in quantum computing, cryptography, information theory, mathematics and physics. Recent editions have drawn nearly 1000 participants. In 2027, CQT will host the 30th edition of this conference in Singapore. QIP2027 will take place 20-26 February 2027.

The International Conference on Women in Physics (ICWIP) of the International Union of Pure and Applied Physics (IUPAP) will take place in the National University Singapore (NUS) during 7-11 June 2027, hosted by the Physics Department, NUS and the Centre for Quantum Technologies, Singapore. The ICWIP2027 is the 9th in a series of triennial conferences by IUPAP since 2002 that brings together practitioners from all over the world in order to deliberate on both topics in physics and processes within physics practice, with the goal of transforming physics into a welcoming inclusive enterprise for everyone. The conference will feature inspiring keynote talks by eminent women scholars, sessions where participants can present their own research in physics and on equity and inclusion in physics, interactive workshops to engage with the barriers to equity and inclusion in physics, call-to-action sessions on recommendations for the profession and more...