Fast design and scaling of multi-qubit gates in large-scale trapped-ion quantum computers

TL;DR

This paper presents a polynomial-time method for designing fast, robust, and scalable multiqubit entanglement gates in large trapped-ion quantum computers, addressing key challenges in scaling up qubit numbers while maintaining high fidelity.

Contribution

Introduces a novel polynomial-time approach for designing multiqubit gates in large ion crystals, enabling scalable and efficient quantum computation.

Findings

Gate duration scales linearly with the number of ions

Number of entanglement operations scales quadratically with N

Method reduces drive-power and noise susceptibility

Abstract

Quantum computers based on crystals of trapped ions are a prominent technology for quantum computation. A unique feature of trapped ions is their long-range Coulomb interactions, which can be exploited to realize large-scale multiqubit entanglement gates. However, scaling up the number of qubits, $N$, in these systems, while retaining high-fidelity and high-speed operations, is challenging. Specifically, designing multiqubit entanglement gates in long ion crystals of hundreds of ions involves an NP-hard optimization problem, rendering scale-up not only a technological challenge, but also a conceptual challenge. Here we introduce a method that mitigates this challenge, effectively allowing for a polynomial-time design of fast, robust, and programmable entanglement gates, acting on the entire ion-crystal. We show that while the number of simultaneous entanglement operations scales as $N^2$, the gate duration scales as $N$, leading to a scaling advantage. We use our methods to investigate the drive-power requirements and susceptibility to noise and errors of these multiqubit gates. Our method delineates a path towards scaling up quantum computers based on ion-crystals with hundreds of qubits.