We present a general method for engineering qudits through individually addressable transitions between Zeeman sublevels, achieved by combining a large linear Zeeman shift with a state-dependent light shift. This approach lifts the degeneracy between adjacent states while simultaneously tuning their energy splittings into the radio-frequency (RF) domain, enabling coherent manipulation within the Zeeman manifold using experimentally accessible drive frequencies. As a concrete realization, we investigate the implementation of an SU ( 5 ) encoded in the Zeeman sublevels of the long-lived P 2 3 state of neutral Sr 88 atoms confined in far-detuned, σ − -polarized optical tweezers. Using realistic experimental parameters, we numerically demonstrate full control of the manifold, including initialization into a specific SU ( 5 ) basis state via a multiphoton transfer, coherent state- and site-selective single-qudit rotations driven by RF fields, and fast state-selective optical readout. Our simulations predict state-preparation fidelities of F ≃ 0.99 within less than 1 µ s , single-qudit gate fidelities of F ≃ 0.99 with π -pulse durations of ∼ 1.4 µ s , and fast destructive imaging with durations below 10 µ s under ideal conditions. These results establish a broadly applicable framework for high-fidelity control of Zeeman sublevel-encoded qudits and highlight the P 2 3 manifold in strontium as a promising platform for scalable qudit-based quantum technologies.
We present a general method for engineering qudits through individually addressable transitions between Zeeman sublevels, achieved by combining a large linear Zeeman shift with a state-dependent light shift. This approach lifts the degeneracy between adjacent states while simultaneously tuning their energy splittings into the radio-frequency (RF) domain, enabling coherent manipulation within the Zeeman manifold using experimentally accessible drive frequencies. As a concrete realization, we investigate the implementation of an SU ( 5 ) encoded in the Zeeman sublevels of the long-lived P 2 3 state of neutral Sr 88 atoms confined in far-detuned, σ − -polarized optical tweezers. Using realistic experimental parameters, we numerically demonstrate full control of the manifold, including initialization into a specific SU ( 5 ) basis state via a multiphoton transfer, coherent state- and site-selective single-qudit rotations driven by RF fields, and fast state-selective optical readout. Our simulations predict state-preparation fidelities of F ≃ 0.99 within less than 1 µ s , single-qudit gate fidelities of F ≃ 0.99 with π -pulse durations of ∼ 1.4 µ s , and fast destructive imaging with durations below 10 µ s under ideal conditions. These results establish a broadly applicable framework for high-fidelity control of Zeeman sublevel-encoded qudits and highlight the P 2 3 manifold in strontium as a promising platform for scalable qudit-based quantum technologies.
Quantum systems with more than two levels - so-called qudits - offer increased computational density and reduced circuit complexity compared to qubit-based architectures, but achieving universal and scalable control remains challenging. We propose an all-optical scheme for universal qudit control in trapped neutral atoms in moderate to high magnetic fields, focusing on the fermionic isotope 173Yb (I = 5/2). The strong hyperfine interaction in the 3P1 manifold enables fast and selective Raman transitions between nuclear-spin states in the 1S0 ground-state manifold using a single linearly polarized laser. For each neighboring transition in the qudit manifold, we identify a magic polarization angle that enables coherent, state-selective control while suppressing off-resonant excitations, with operation frequencies exceeding 100 kHz. Combined with phase-shift operations, this provides universal control of the full single-qudit space. We further discuss compatible two-qudit gates based on the Rydberg blockade mechanism, completing a universal gate set, and analyze state-selective readout schemes compatible with the proposed protocol. Our results identify 173Yb as a promising platform for high-fidelity, all-optical qudit-based quantum information processing.
Bichromatic Tweezers for Qudit Quantum Computing in 87Sr
Neutral atoms have become a competitive platform for quantum metrology, simulation, sensing, and computing. Current magic trapping techniques are insufficient to engineer magic trapping conditions for qudits encoded in hyperfine states with J=0, compromising qudit coherence. In this paper we propose a scheme to engineer magic trapping conditions for qudits via bichromatic tweezers. We show it is possible to suppress differential light shifts across all magnetic sublevels of the 5s5p3P2 state by using two carefully chosen wavelengths (with comparable tensor light shift magnitude and opposite sign) at an appropriate intensity ratio, thus suppressing light-shift induced dephasing, enabling scalar magic conditions between the ground state and 5s5p3P2, and tensor magic conditions for qudits encoded within it. Furthermore, this technique enables robust operation at the tensor magic angle 54.7∘ with linear trap polarization via reduced sensitivity to uncertainty in experimental parameters. We expect this technique to enable new loading protocols, enhance cooling efficiency, and enhance nuclear spins' coherence times, thus facilitating qudit-based quantum computing in 87Sr in the 5s5p3P2 manifold.
Quantum devices comprised of elementary components with more than two stable levels—so-called qudits—enrich the accessible Hilbert space, enabling applications ranging from fault-tolerant quantum computing to simulating complex many-body models. While several quantum platforms are built from local elements that are equipped with a rich spectrum of stable energy levels, schemes for the efficient control and entanglement of qudits are scarce. Importantly, no experimental demonstration of multiqudit control has been achieved to date in neutral atom arrays. Here, we propose a general scheme for controlling and entangling qudits and perform a full analysis for the case of qutrits, encoded in ground and metastable states of alkaline earth atoms. We find an efficient implementation of single-qudit gates via the simultaneous driving of multiple transition frequencies. For entangling operations, we provide a concrete and intuitive recipe for the controlled- Z ( C Z ) gate for any local dimension d , realized through alternating single qudit and entangling pulses that simultaneously drive up to two Rydberg transitions. We further prove that two simultaneous Rydberg tones are, in general, the minimum necessary for implementing the C Z gate with a global drive. The pulses we use are optimally controlled, smooth, and robust to realistic experimental imperfections, as we demonstrate using extensive noise simulations. This amounts to a minimal, resource-efficient, and practical protocol for realizing a universal set of gates. Our scheme for the native control of qudits in a neutral atom array provides a high-fidelity route toward qudit-based quantum computation, ready for implementation on near-term devices.
Neutral atoms are a ubiquitous platform for various quantum sciences with applications in quantum computing, simulation, and metrology across many different atomic species. In these systems, control over the electronic states is given by suitable laser pulses typically applied at the single-particle level. Here, we present fast coherent control over the meta-stable clock states in bosonic strontium-88 using two- and three-photon couplings. Compared to the direct single-photon drive on these transitions, the realistically achievable Rabi frequencies are substantially higher at significantly relaxed magnetic field strength. By applying a magnetic quantization axis under a judiciously chosen angle with respect to the linear trap polarization, we realize an optical qutrit comprising the ground state 1S0 as well as both clock states 3P0 and 3P2, and characterize in detail the coherence of the system. Remarkably, the observed coherence time on the fine-structure qubit (given by the 3P0 and 3P2,mj=0 states) of 715(30) ms demonstrates, for the first time, that state-of-the-art coherence times are compatible with tweezer-based polarizability-engineered trapping potentials, which is applicable across a broad range of wavelengths and atomic species. We identify laser phase noise as the main limitation of the current operation fidelity and discuss methods for characterizing, modelling, and compensating optical phase noise. The multi-photon couplings not only allow for substantially faster Rabi frequencies under realistic experimental conditions, but additionally offer controlled dissipation via the 3P1 state, which we use to demonstrate a measurement-free qubit reset. Combined with three-photon couplings to the 3P2 clock state, we realize resolved sideband cooling in an optical lattice potential and benchmark the fine-structure qubit at various infrared wavelengths. In addition, we introduce a hybrid lattice-tweezer setup and demonstrate the preparation of programmable atom configurations in a single plane of the two-dimensional optical lattice potential. Using single-site addressing with optical tweezers, we present a protocol for the iterative assembly of large-scale atom arrays. Furthermore, we use the lattice-tweezer combination to continuously operate a configurable atom array, which provides means to overcome scaling limitations by repeatedly adding atoms to the system and enables entirely novel approaches to operating neutral-atom arrays. To enable reliable image processing with a fast reconstruction of the lattice occupation, we introduce a novel algorithm based on a convolutional neural network, which provides a rapid and noise-resilient reconstruction compatible with arbitrary lattice geometries. Moreover, we benchmark a new phase-only spatial light modulator based on a micromirror array, which paves the way towards holographic beam shaping at fast update rates compatible with a broad range of wavelengths, including the ultraviolet spectral range.
Neutral atoms are promising candidates to store and manipulate quantum information. In this thesis we examine several problems related to the control of neutral atoms for quantum computation and simulation. In the first problem we show how the transport of atoms in an optical lattice can be controlled through variation of the polarization of the optical lattice and the application of global microwave pulses. This type of control control is a first step in many of the schemes for quantum computation and quantum simulation. We show that with the available tools for global control, the synthesis of any unitary transformation, consistent with translational invariance, may be performed and provide an explicit method for carrying this out. In the second problem, we study a spectroscopic method for probing atomic interactions that may form the basis for two-qudit quantum logic gates. The confinement of atoms required to perform quantum computation can strongly affect how they interact. Probing the nature of those confinement-induced effects is a first step towards quantum computing with neutral atoms. Transport of the atoms to overlapping wells is achieved through microwave pulses that drive population between hyperfine levels in a lin-perp-lin polarization-gradient lattice. By measuring the amount of population transferred into certain excited states, we can detect changes in the spectrum of the two-atom system induced by the interaction. In the third problem, we consider a cloud of cold atoms driven by both microwave and radio-frequency magnetic fields. The large number of spin sublevels available in individual atoms makes them candidates for a qudit-based quantum computer. Because the applied fields that drive the system may be inhomogeneous, the collection of atoms forms an ensemble of different qudits. Borrowing ideas developed for NMR control, we show how to drive the ensemble through a given evolution. We show that even in the presence of large experimental errors, state preparation may be achieved with high fidelities. We also show that intentionally applied variations in spatial magnetic fields can be used to synthesize different states in different regions of space.
We report on the first realization of a novel neutral atom qubit encoded in the spin-orbit coupled metastable states ^{3}P_{0} and ^{3}P_{2} of a single ^{88}Sr atom trapped in an optical tweezer. Raman coupling of the qubit states promises rapid single-qubit rotations on par with the fast Rydberg-mediated two-body gates. We demonstrate preparation, readout, and coherent control of the qubit. In addition to driving Rabi oscillations bridging an energy gap of more than 17 THz using a pair of phase-locked clock lasers, we also carry out Ramsey spectroscopy to extract the transverse qubit coherence time T_{2}. When the tweezer is tuned into magic trapping conditions, which is achieved in our setup by tuning the tensor polarizability of the ^{3}P_{2} state via an external control magnetic field, we measure T_{2}=1.2 ms. A microscopic quantum mechanical model is used to simulate our experiments including dominant noise sources. We identify the main constraints limiting the observed coherence time and project improvements to our system in the immediate future. Our Letter opens the door for a so-far-unexplored qubit encoding concept for neutral atom-based quantum computing.