Multi-GHz repetition rate, multi-watt average power, ultraviolet laser pulses for fast trapped-ion entanglement operations

TL;DR

This paper presents a novel ultrafast ultraviolet laser source based on a frequency comb, capable of enabling rapid, high-fidelity entangling gates in trapped-ion quantum computing, significantly accelerating quantum operations.

Contribution

The authors engineered a high-repetition-rate, multi-watt ultraviolet laser source using a frequency comb, tailored for fast entangling gates in trapped-ion systems, overcoming previous technical limitations.

Findings

Laser source generates 5 GHz pulses at 393.3 nm with 800 pJ energy.

Demonstrated rapid adiabatic passage in Ca$^+$ ion using a single chirped pulse.

Simulations show potential for gate times faster than trap periods with errors near 10^{-4}.

Abstract

The conventional approach to perform two-qubit gate operations in trapped ions relies on exciting the ions on motional sidebands with laser light, which is an inherently slow process. One way to implement a fast entangling gate protocol requires a suitable pulsed laser to increase the gate speed by orders of magnitude. However, the realization of such a fast entangling gate operation presents a big technical challenge, as such the required laser source is not available off-the-shelf. For this, we have engineered an ultrafast entangling gate source based on a frequency comb. The source generates bursts of several hundred mode-locked pulses with pulse energy $\sim$800 pJ at 5 GHz repetition rate at 393.3 nm and complies with all requirements for implementing a fast two-qubit gate operation. Using a single, chirped ultraviolet pulse, we demonstrate a rapid adiabatic passage in a Ca$^+$ ion. To verify the applicability and projected performance of the laser system for inducing entangling gates we run simulations based on our source parameters. The gate time can be faster than a trap period with an error approaching $10^{-4}$.