Seokjun Hong

A major challenge for quantum computers is the scalable simultaneous execution of quantum gates. One approach to address this in trapped ion quantum computers is the implementation of quantum gates based on static magnetic field gradients and global microwave fields. In this paper, we present the fabrication of surface ion traps with integrated copper current carrying wires embedded inside the substrate below the ion trap electrodes, capable of generating high magnetic field gradients. The copper layer's measured sheet resistance of 1.12 m$Ω$/sq at room temperature is sufficiently low to incorporate complex designs, without excessive power dissipation at high currents causing a thermal runaway. At a temperature of 40 K the sheet resistance drops to 20.9 $μΩ$/sq giving a lower limit for the residual resistance ratio of 100. Continuous currents of 13 A can be applied, resulting in a simulated magnetic field gradient of 144 T/m at the ion position, which is 125 $μ$m from the trap surface for the particular anti-parallel wire pair in our design.

Trapped atomic ions are a proven and powerful tool for the fundamental research of quantum physics. They have emerged in recent years as one of the most promising candidates for several practical technologies including quantum computers, quantum simulators, atomic clocks, mass spectrometers and quantum sensors. Advanced fabrication techniques, taken from established and nascent disciplines, are being deployed to create novel, reliable devices with a view to large scale integration and commercial compatibility. This review will cover the fundamentals of ion trapping before proceeding with a discussion of the design of ion traps for the aforementioned applications. We will analyse current microfabrication techniques that are being utilised, as well as various considerations which motivate the choice of materials and processes. Finally, we discuss current efforts to include advanced, on-chip features into next generation ion traps.

We present a numerical study of a MEMS-based design of a fiber cavity integrated with an ion trap system. Each fiber mirror is supported by a microactuator that controls the mirror's position in three dimensions. The mechanical stability is investigated by a feasibility analysis showing that the actuator offers a stable support of the fiber. The actuators move the fibers' positions continuously with a stroke of more than 10 $μ$m, with mechanical resonance frequencies on the order of kHz. A calculation of the trapping potential shows that a separation between ion and fiber consistent with strong ion-cavity coupling is feasible. Our miniaturized ion-photon interface constitutes a viable approach to integrated hardware for quantum information.