Abstract

Device miniaturization is a challenge that raises new issues because the scaling laws valid in the macroscopic range might fail, for instance due to the emergence of a new characteristic length. Even the simple case of the electric field in the vicinity of a conductor surface can exhibit anomalous behavior caused by small inhomogeneities of the electric potential on the surface. These field fluctuations are crucial in the studies of short distance phenomena such as the measurement of the Casimir-Polder force, studies of non contact friction[1], gravitational forces and contact potentials. In a different context, recent success in quantum information experiment with trapped ions motivated the fabrication of micro-traps in order to fulfill the scalability requirement of a quantum computer. In such devices a set of micro-fabricated conducting electrodes generates an oscillating electric field that traps laser-cooled ions in a harmonic potential well, at a distance, d, of the surface. In this situation the presence of a fluctuating electric field affects the ion motion inducing a heating. This heating fixes a limit on the achievable fidelity of ion based quantum gates. One might try to account for this heating rate by considering typical electric noise sources in conductors, among which the most likely is Johnson noise. However, measured heating rates are orders of magnitude larger than the expected contribution of the Johnson noise. Moreover, Johnson noise would induce a heating rate that scales as d⁻², whereas the observed one is partially consistent with a d⁻⁴ scaling, as would be expected from a random distribution of charges, leading to the notion of patch potentials [2]. However, this approach fails at small distances, where a d⁻¹ scaling is observed[l]. Recent experiments[3] suggest that indeed the surface quality plays a dominant role in this anomalous heating.

© 2009 IEEE