Progress Report
Fault-tolerant Quantum Computing with Photonically Interconnected Ion Traps7. Development of quantum interfaces between ions and atoms
Progress until FY2022
1. Outline of the project
Linking remote ion-trap modules is key ingredient for scaling the number of ion qubits towards large-scale fault-tolerant quantum computation. A technology for coupling a single ion to a different quantum system is indispensable for this purpose. In this research project, we develop a quantum interface for ions and neutral atoms based on Rydberg excitation. We aim to use ultracold atoms as a mobile qubit transmitter which enables connection between remote ion qubits. We expect that such a quantum interface for a hybrid quantum system offer a novel strategy for scaling the ion qubits in a more efficient and flexible way.
2. Outcome so far
We developed an apparatus for simultaneous capturing of ions and atoms (Sr ions and Sr atoms). First, we designed and built a linear Paul trap, which has a three-dimensional structure with segmented electrodes, and the trap is assembled in a vacuum chamber as found in Fig.2. This trap enables tight confinement of trapped ions into a Lamb-Dicke regime. Combined with a subsequent laser cooling, the ions can be initialized in the motional ground state. This is an important step for coherent control of the ion’s internal and vibrational degrees of freedoms, i.e., qubit states.
In parallel, we designed a vacuum system for trapping ultracold atoms (Fig.3). A hot beam of Sr atoms from an atomic oven is initially laser cooled via the Zeeman slowing section. The atoms are subsequently captured and further cooled in a magneto-optical trap (MOT) in a main chamber. Combined with a narrow-line MOT, the atom temperature at this stage reaches a sub-millikelvin regime. The design includes a set of electrodes and a micro-channel plate for ionization and detection of atoms in a Rydberg state. The field electrodes are also useful for nulling the excess electric field at the atom-trap center, which enables stable trapping of Rydberg atoms. We are currently working on trapping experiment of ions and atoms with this setup.
3. Future plans
We first plan to establish a stable trapping of a single ions and an ensemble of ultracold atoms. Performing Rydberg spectroscopy is also desired to characterize the level structure of the highly excited states. Such spectroscopic information is important to predict the target Rydberg state for exploring a strong atom-ion interaction. At the final stage of the project, we plan to demonstrate Rydberg-blockade gates in an atom-ion hybrid system. This opens an opportunity for utilizing neutral atoms as supportive qubits in ion-based quantum devices.