Realizing coherently convertible dual-type qubits with the same ion species*

 For large-scale ion-trap based quantum computers and networks, it is critical to have two types of qubits, one for computation and storage, while the other for auxiliary operations like runtime qubit detection, sympathetic cooling, et al. Dual-type qubits have previously been realized in hybrid systems using two ion species, which, however, introduces significant experimental challenges for laser setup, gate operations as well as the control of the fraction and positioning of each qubit type within an ion crystal. Here we solve these problems by implementing two coherently-convertible qubit types using the same ion species. We encode the qubits into two pairs of clock states of the ¹⁷¹Yb⁺ ions, and achieve fast and high-fidelity (about 99.5%) conversion between the two types using narrow-band lasers. We further demonstrate that operations on one qubit type, including sympathetic cooling, gates and qubit detection, have crosstalk errors less than 0.06% on the other type.