Mixed-Species Logic Gates and High-Fidelity Universal Gate Set for Trapped-Ion Qubits

Colin Bruzewicz, Jonathon A. Sedlacek, Jules Stuart +3 more

Yinnon Glickman, Nitzan Akerman, Shlomi Kotler +2 more

Ting Rei Tan, John Gaebler, Yiheng Lin +4 more

Ting Rei Tan

Quantum entangling logic gates are key ingredients for the implementation of a quantum information processing device. In this thesis, we focus on experimental implementations of three types of entangling geometric-phase gates with trapped ions, which rely on the effective spin-spin interactions generated with state-dependent forces. First, a mixed-species entangling gate is demonstrated using a 9Be+ and a 25Mg+ ion to create a Bell state with a fidelity of 0.979(1). Combined with single-qubit gates, we use this mixed-species gate to implement controlled-NOT and SWAP gates. Second, we implement a high-fidelity universal gate set with 9Be+ ions. Single-qubit gates with error per gate of 3.8(1)x10-5 are achieved. By creating a Bell state with a deterministic two-qubit entangling gate, we deduce a gate error as low as 8(4)x10-4. Third, a novel two-qubit entangling gate with dynamical decoupling built-in is demonstrated with a fidelity of 0.974(4). This gate is robust against qubit dephasing errors and offers simplifications in experimental implementation compared to some other gates with trapped ions. Errors in the above implementations are evaluated and methods to further reduce imperfections are discussed. In a separate experiment, correlated measurements made on pairs of ions violate a "chained" Bell inequality obeyed by any local-realistic theory. The lowest chained Bell inequality parameter determined from our measurements is 0.296(12), this value is significantly lower than 0.586, the minimum value derived from a perfect Clauser-Horne-Shimony-Horne (CHSH) Bell inequality experiment. Furthermore, our CHSH Bell inequality results provide a device-independent certification of the deterministically created Bell states.

Zain Mehdi, Varun Vaidya, Isabelle Savill-Brown +6 more

The authors propose the use of ultrafast laser pulses to rapidly transfer quantum information between noisy network qubits and stable memory qubits in trapped-ion quantum networks. The authors demonstrate that high-fidelity and high-speed quantum logic operations are achievable between a broad range of mixed-species ion pairs, which allows multiple specialized qubits to be employed in quantum networks of trapped-ion processors.

Vera M. Schäfer, Christopher J. Ballance, K. Thirumalai +4 more