This paper presents a method for high-fidelity control and measurement of a spin-7/2 system encoded in a superconducting transmon qudit. The researchers use a modified transmon design with a deep cosine potential to encode qudit states with long coherence times, enabling high-fidelity control. They implement multi-tone dispersive readout to achieve single-shot readout of eight states with 88.3% assignment fidelity. By leveraging the strong nonlinearity of the transmon, they simultaneously address each transition and realize a spin displacement operator. Combining this with a virtual SNAP gate, they perform arbitrary single-qudit unitary operations in O(d) physical pulses, achieving gate fidelities of 0.997 to 0.989 for qudits of size j = 1 to j = 7/2. These native qudit operations can be combined with entangling operations to explore qudit-based error correction or simulations of lattice gauge theories. The multi-frequency approach to qudit control and measurement can be extended to other platforms with multi-level systems coupled to a cavity, serving as a building block for efficient qudit-based quantum computation and simulation. The study demonstrates high-fidelity spin displacement operations, enabling direct Wigner tomography of qudit states and verifying the expected behavior of the Wigner function. The researchers also propose spin displacements as primitive gates for efficient qudit computation, achieving high-fidelity operations with a single displacement pulse and virtual phase rotations. They demonstrate the use of spin cat states and perform randomized benchmarking to evaluate the fidelity of displacement operations, achieving high fidelities for different qudit dimensions. The results show that the multi-frequency approach enables efficient and high-fidelity qudit control and measurement, with potential applications in quantum computing and simulation.This paper presents a method for high-fidelity control and measurement of a spin-7/2 system encoded in a superconducting transmon qudit. The researchers use a modified transmon design with a deep cosine potential to encode qudit states with long coherence times, enabling high-fidelity control. They implement multi-tone dispersive readout to achieve single-shot readout of eight states with 88.3% assignment fidelity. By leveraging the strong nonlinearity of the transmon, they simultaneously address each transition and realize a spin displacement operator. Combining this with a virtual SNAP gate, they perform arbitrary single-qudit unitary operations in O(d) physical pulses, achieving gate fidelities of 0.997 to 0.989 for qudits of size j = 1 to j = 7/2. These native qudit operations can be combined with entangling operations to explore qudit-based error correction or simulations of lattice gauge theories. The multi-frequency approach to qudit control and measurement can be extended to other platforms with multi-level systems coupled to a cavity, serving as a building block for efficient qudit-based quantum computation and simulation. The study demonstrates high-fidelity spin displacement operations, enabling direct Wigner tomography of qudit states and verifying the expected behavior of the Wigner function. The researchers also propose spin displacements as primitive gates for efficient qudit computation, achieving high-fidelity operations with a single displacement pulse and virtual phase rotations. They demonstrate the use of spin cat states and perform randomized benchmarking to evaluate the fidelity of displacement operations, achieving high fidelities for different qudit dimensions. The results show that the multi-frequency approach enables efficient and high-fidelity qudit control and measurement, with potential applications in quantum computing and simulation.