A method of an on-demand beamsplitter for trapped-ion quantum computers

Quantum information processing using local modes of trapped ions has been applied to implementing bosonic quantum error correction codes and conducting efficient quantum simulation of bosonic systems. However, control of entanglement among local modes remains difficult because entanglement among resonant local modes is governed by the Coulomb interaction, which is not switchable. We propose a method of a beamsplitter for a trapped-ion architecture, where the secular frequency of each mode is dynamically controllable. The neighboring modes are far detuned except when the beamsplitter needs to be applied to them. We derive the analytical formula of the proposed procedure and numerically confirm its validity.

💡 Research Summary

The paper addresses a fundamental challenge in trapped‑ion continuous‑variable quantum information processing: the inability to switch off the Coulomb‑mediated phonon hopping that naturally entangles local motional modes. Existing schemes either rely on permanent phonon hopping, which cannot be turned off, or require complex laser‑driven sideband operations that are not scalable for many ions. The authors propose an “on‑demand beamsplitter” that enables selective, controllable entanglement between neighboring local modes while keeping all other modes far detuned and effectively decoupled.

The core idea is to make the secular frequency of each ion’s radial (X‑axis) mode dynamically tunable via fast modulation of the DC voltages on a surface‑electrode trap, as demonstrated in prior work (Ref.