Quantum information processing in scalable microfabricated surface ion traps
Dr. Peter L.W. Maunz (Sandia National Laboratories, Albuquerque, USA)

Calculating properties of molecules and solid state systems from first principles is intractable on classical computers because the problem size scales exponentially with the number of particles. Quantum computing, a different model of computation that uses quantum states for calculations might offer a way to solve currently intractable problems in quantum chemistry and solid state physics.

Trapped ions feature long-lived and well-isolated quantum states to implement qubits. Furthermore, small quantum algorithms have been realized in this system with high fidelity. Scaling trapped ion systems to the number of qubits required to outperform a classical computer is envisioned by using large segmented ion traps. Microfabricated surface traps enable a wide range of trapping geometries and provide a scalable platform for trapped ion Quantum Information Processing (QIP). However, the feasibility of using surface traps for QIP has been a point of contention because the close proximity of the ions to trap electrodes increases heating rates and might lead to laser-induced charging of the trap.

Using Sandia's High-Optical-Access surface trap, we demonstrate robust single-qubit gates, both laser- and microwave-based. Our gates are accurately characterized by Gate Set Tomography (GST) and we report the first diamond norm measurements below the fault-tolerance threshold [1, 2]. Extending these techniques, we've realized a Mølmer-Sørensen two-qubit gate that is stable for several hours. This stability has allowed us to perform the first GST measurements of a two-qubit gate, yielding a process fidelity of 99.58(6)%. These results demonstrate that surface traps form a viable way for scaling trapped ion QIP.

[1] P. Aliferis and A. W. Cross, Phys. Rev. Lett. 98, 220502 (2007) [2] R. Blume-Kohout et al. arXiv:1606.07674