Expanding the Trapped-Ion Toolbox: Two-Mode Squeezing and Metastable Qudits

Trapped ions are a leading platform for quantum information processing, typically using qubits embedded within the electronic ground state or defined across an optical transition and coupled to a single quantized motional mode. These optical transitions and motional modes also form the basis for world-class timekeeping and displacement sensing, respectively. All these applications benefit from larger ion numbers, but motional mode crowding and heating place practical limits on the useful number of ions in a given trap. Another approach is to use more of each ions’ available Hilbert space. We first use two-mode motional squeezing to implement an SU(1,1) interferometer with phase sensitivity 4.5(2) dB below the standard quantum limit. Then, we will discuss co-trapping and simultaneous operation of qubits defined in ground and metastable manifolds of 40Ca+ and preliminary SPAM results for a six-level metastable qudit. Finally, we will explore possible uses of these new capabilities to study squeezing in small systems and perform enhanced sensing protocols.