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Trapped-ion quantum logic gates based on oscillating magnetic fields
C. Ospelkaus, C. E. Langer, J. M. Amini, K. R. Brown, D. Leibfried, D. J. Wineland
TL;DR
Laser-mediated trapped-ion gates face laser-control overhead and spontaneous-emission decoherence. This paper analyzes single- and multi-qubit gates driven by oscillating magnetic fields in surface-electrode traps. It estimates a 20 µs gate at 30 µm and argues that gate durations comparable to laser-mediated gates are achievable with current trap technology.
Problem
Laser-induced trapped-ion gates require substantial laser-beam power and control as register sizes scale, and their fidelities are limited by fluctuations in classical parameters.
Source: p. 1Method
The paper analyzes universal single- and multi-qubit gates using oscillating magnetic fields and σϕσϕ or σzσz couplings, including their integration with surface-electrode traps.
Source: p. 1Results
At 30 µm, a 5 MHz-mode σϕσϕ gate is estimated at 20 µs with 1.7 A; comparable laser-mediated gate durations are achievable with current trap technology.
Source: pp. 3–4Takeaways & Limitations
Magnetic-field gates avoid spontaneous-emission decoherence and may eliminate the need for near-ground-state cooling.
Source: p. 4For σzσz gates on a center-of-mass mode, oscillating electrode potentials can drive motion and create large, difficult-to-control phases.
Source: p. 3
Abstract
from arXiv · showhide
Oscillating magnetic fields and field gradients can be used to implement single-qubit rotations and entangling multi-qubit quantum gates for trapped-ion quantum information processing (QIP). With fields generated by currents in microfabricated surface-electrode traps, it should be possible to achieve gate speeds that are comparable to those of optically induced gates for realistic distances between the ion crystal and the electrode surface. Magnetic-field-mediated gates have the potential to significantly reduce the overhead in laser beam control and motional state initialization compared to current QIP experiments with trapped ions and will eliminate spontaneous scattering, a fundamental source of decoherence in laser-mediated gates.