Over the years, trapped ion have emerged as one of the premier candidates for universal \nquantum simulation due to its long coherence time, low initialization and detection errors, \nrobust high-fidelity gate sets and fully connected yet tunable spin-graph. In this thesis \nwe exclusively focus on the generation of the trapping potential in a four-rod trap, one of \nthe most commonly studied ion-trapping architecture. We elaborate the fabrication of the \ntrapping electrodes using electro-etching techniques and explore the underlying mechanism \nin details. We discuss how these electrodes are powered by DC and RF field to generate \nthe confining potential responsible for trapping the ions of interest in 3D. We conclude by \nstudying how this trapping potential can be modified by external means like using an optical \ntweezer. Employing such an optical tweezer we propose a new quantum-thermodynamic \nprotocol which shall allow us to experimentally access the thermal properties of a mixed specie \nion chain using a single-specie ion chain. The scheme is based on Jarynski's equality \nand obviates the need to trap dual-ionic species as far as illustrating the mechanical properties \nof the chain are concerned. We present results ratifying the utility of the proposal. \nThe scheme is useful to obtain mode-specific thermal properties hitherto unexplored experimentally.
Over the years, trapped ion have emerged as one of the premier candidates for universal \nquantum simulation due to its long coherence time, low initialization and detection errors, \nrobust high-fidelity gate sets and fully connected yet tunable spin-graph. In this thesis \nwe exclusively focus on the generation of the trapping potential in a four-rod trap, one of \nthe most commonly studied ion-trapping architecture. We elaborate the fabrication of the \ntrapping electrodes using electro-etching techniques and explore the underlying mechanism \nin details. We discuss how these electrodes are powered by DC and RF field to generate \nthe confining potential responsible for trapping the ions of interest in 3D. We conclude by \nstudying how this trapping potential can be modified by external means like using an optical \ntweezer. Employing such an optical tweezer we propose a new quantum-thermodynamic \nprotocol which shall allow us to experimentally access the thermal properties of a mixed specie \nion chain using a single-specie ion chain. The scheme is based on Jarynski's equality \nand obviates the need to trap dual-ionic species as far as illustrating the mechanical properties \nof the chain are concerned. We present results ratifying the utility of the proposal. \nThe scheme is useful to obtain mode-specific thermal properties hitherto unexplored experimentally.
We propose an experimental architecture where an array of optical tweezers affords site-dependent control over the confining potential of a conventional radio-frequency ion trap. The site-dependent control enables programmable manipulation of phonon modes of ions, with many potential applications in quantum information processing (QIP) and thermodynamics. We describe protocols for programming the array of optical tweezers to attain a set of target phonon modes with high accuracy. We propose applications of such controls in simulating quantum thermodynamics of a particle of programmable effective mass via Jarzynski's equality and improving the efficiency of sympathetic cooling and quantum logic gates in a multispecies ion system of disparate masses. We discuss the required optical parameters in a realistic ion trap system and potential adverse effects of optical tweezers in QIP. Our scheme extends the utility of trapped ions as a platform for quantum computation and simulation.
Ion traps and optical tweezers have emerged as highly promising technologies in the development of quantum computing, enabling precise control over qubits through electromagnetic and optical confinement. This paper explores the fundamental principles, advantages, and limitations of ion traps, including Paul and Penning configurations, and evaluates their role in modern quantum architectures. Particular emphasis is placed on coherence time, fidelity, and all-to-all connectivity, which make trapped ions a leading qubit candidate despite challenges in scalability and optical complexity. The work also examines optical tweezers, which use tightly focused laser beams to trap and manipulate ions and atoms with high precision, facilitating scalable arrays of qubits. Furthermore, hybrid traps that integrate optical tweezers with Paul traps are discussed as promising solutions to mitigate Radio-Frequency (RF) micromotion and enhance stability for cold ion–atom systems. Python-based simulations are presented to illustrate ion dynamics under Brownian motion, electric fields, and Gaussian laser traps, demonstrating how trap strength directly affects oscillation amplitude and confinement. Results confirm that stronger optical potentials reduce oscillation amplitude, while weaker traps lead to ion escape, aligning with theoretical predictions. Overall, this study highlights how the interplay of electromagnetic and optical techniques advances the frontier of quantum information science, with direct implications for computation, communication, and simulation.
In this thesis, the next generation of the ion trapping setup has been designed, constructed, and successfully implemented for studying quantum information science at the University of Bonn. The new setup is designed to include an optical cavity as the endcap electrodes of a linear radio-frequency ion trap. In view of this, a novel method to drive the linear ion trap is invented to apply two-phase radio-frequency voltage. In addition to this, a new method to directly bias all the electrodes of the ion trap with DC voltages is implemented in order to control the static electric fields along all directions. Using these methods, over 6 ytterbium ions in a linear Coulomb crystal can been trapped, and radial trapping frequencies of over 1.2 MHz have been observed using the aforementioned methods. Low axial-micromotion for over 65 µm along the axis of the ion trap has been observed, although the endcap electrodes are just as close to the trapped ions as the linear electrodes. In view of finding a novel approach for photonic interfacing the Yb ions, the lower-lying energy levels involving inner-shell electron excitations are investigated in this thesis. By considering their properties, the 2D3/2 → 4f13 (2Fo5/2)5d6s(3D) 3[5/2]o3/2 transition is successfully interrogated using direct laser excitation for the first time to the best of my knowledge. The transition frequency is measured to be 603013350 ± 162 MHz for the isotope 174Yb. In addition to the study of quantum information science, the new ion trap -- optical cavity setup is also considered for the experimental investigation of microscopic thermodynamics. In view of this, the Hamiltonian of the complete system is derived and compared with the theoretical models of Hamiltonian engines. Various non-linear terms occurring in the system Hamiltonian are described for studying the concept of ignition in a future single ion engine in our linear ion trap.
Quantum computing promises solutions to some of the world's most important problems that classical computers have failed to address. The trapped-ion-based quantum computing platform has a lot of advantages for doing so: ions are perfectly identical and near-perfectly isolated, feature long coherent times, and allow high-fidelity individual laser-controlled operations. One of the greatest remaining obstacles in trapped-ion-based quantum computing is the issue of scalability. The approach that we take to address this issue is a modular architecture: separate ion traps, each with a manageable number of ions, are interconnected via photonic links. To avoid photon-generated crosstalk between qubits and utilize advantages of different kinds of ions for each role, we use two distinct species - ¹⁷¹Yb⁺ as memory qubits and ¹³⁸Ba⁺ as communication qubits. The qubits based on ¹⁷¹Yb⁺ are defined within the hyperfine "clock" states characterized by a very long coherence time while ¹³⁸Ba⁺ ions feature visible-range wavelength emission lines. Current optical and fiber technologies are more efficient in this range than at shorter wavelengths. We present a theoretical description and experimental demonstration of the key elements of a quantum network based on the mixed-species paradigm. The first one is entanglement between an atomic qubit and the polarization degree of freedom of a pure single photon. We observe a value of the second-order correlation function g⁽²⁾(0) = (8.1 ± 2.3)⨉10⁻⁵ without background subtraction, which is consistent with the lowest reported value in any system. Next, we show mixed-species entangling gates with two ions using the Mølmer-Sørensen and Cirac-Zoller protocols. Finally, we theoretically generalize mixed-species entangling gates to long ion chains and characterize the roles of normal modes there. In addition, we explore sympathetic cooling efficiency in such mixed-species crystals. Besides these developments, we demonstrate new techniques for manipulating states within the D₃⸝₂-manifold of zero-nuclear-spin ions - a part of a protected qubit scheme promising seconds-long coherence times proposed by Aharon et al. in 2013. As a next step, we provide a detailed description of the protocols for three- and four-node networks with mixed species, along with a novel design for the third trap with in-vacuum optics to optimize light collection.
Quantum simulation is the process of using a highly controllable quantum system to simulate another less controllable system. Quantum simulation can provide insights into the properties and dynamics of complex many-body systems. Trapped ion platform is one of the leading candidates for a quantum simulator due to its properties such as ease of isolation, preparation and manipulation. Simulating high dimensional spin systems enables us to study the various physical phenomena in higher geometries. Previous proposals for simulating higher dimensions require experimental resources that don't scale favourably with the system. In this thesis, we propose a hybrid (digital-analog) approach to simulate an effective 2D lattice from a 1D chain of trapped ions. In the initial geometry, the ions interact with each other through a flip-flop kind of interactions generated using a global Molmer-Sorensen scheme. A series of single qubit gates are used to rescale and suppress the interactions in the initial chain to simulate the target geometry. These gates are applied using a laser field gradient which generates a site-dependent AC stark shift. I discuss the construction of this protocol in detail and the theoretical results for the case of 6, 9 and 16 ions. I also show that the number of gates and also the Stark gradient scale linearly with the system size. \n \nExperimental implementation of an ion trap quantum simulator has various challenges, one of the which is the laser frequency stabilization within a fraction of transition linewidth. Traditionally, this is done by locking the lasers to an atomic transition. In this thesis, I discuss two alternative schemes for locking the laser frequencies used to build a 171Yb+ ion quantum simulator. One of these solutions uses a commercial wavemeter as a measuring device for the frequency and feedbacks the lasers based on this measurement. I discuss the layout of this scheme and some results. Other solution uses a Fabry Perot (FP) cavity to transfer the stability of a stable laser to an unstable laser. In this thesis, I discuss the construction, optical layout and transmission measurements of a home-built FP cavity.
Recent advances in quantum information processing with trapped ions have demonstrated the need for new ion trap architectures capable of holding and manipulating chains of many (>10) ions. Here we present the design and detailed characterization of a new linear trap, microfabricated with scalable complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited to this challenge. Forty-four individually controlled dc electrodes provide the many degrees of freedom required to construct anharmonic potential wells, shuttle ions, merge and split ion chains, precisely tune secular mode frequencies, and adjust the orientation of trap axes. Microfabricated capacitors on dc electrodes suppress radio-frequency pickup and excess micromotion, while a top-level ground layer simplifies modeling of electric fields and protects trap structures underneath. A localized aperture in the substrate provides access to the trapping region from an oven below, permitting deterministic loading of particular isotopic/elemental sequences via species-selective photoionization. The shapes of the aperture and radio-frequency electrodes are optimized to minimize perturbation of the trapping pseudopotential. Laboratory experiments verify simulated potentials and characterize trapping lifetimes, stray electric fields, and ion heating rates, while measurement and cancellation of spatially-varying stray electric fields permits the formation of nearly-equally spaced ion chains.