Electromagnetic properties of thin metallic films

Abstract

We compute the electromagnetic fluctuations due to evanescent-wave Johnson noise in the vicinity of a thin conducting film, such as a metallic gate or a 2-dimensional electron gas. This noise can decohere a nearby qubit and it is also responsible for Casimir forces. We have improved on previous calculations by including the nonlocal dielectric response of the film, which is an important correction at short distances. Remarkably, the fluctuations responsible for decoherence of charge qubits from a thin film are greatly enhanced over the case of a conducting half space. The decoherence times can be reduced by over an order of magnitude by decreasing the film thickness. This appears to be due to the leakage into the vacuum of modes that are well localized in the perpendicular direction. There is no corresponding effect for spin qubits (magnetic field fluctuations). We also show that a nonlocal dielectric function naturally removes the divergence in the Casimir force at vanishing separation between two metallic sheets or halfspaces. In the separation regime where a local and nonlocal treatment are noticeably distinct, the Casimir attraction between two thin sheets and two halfspaces are practically indistinguishable for any physical film thickness.

References in corpus (6)

• Graphene-based photovoltaic cells for near-field thermal energy conversion
• Effects of spatial dispersion in near-field radiative heat transfer between two parallel metallic surfaces
• Anomalous temperature dependence of the Casimir force for thin metal films
• Qubit relaxation from evanescent-wave Johnson noise
• Relaxation in quantum dots due to evanescent-wave Johnson noise from a metallic backgate
• Casimir Force between Atomically Thin Gold Films

Cited by in corpus (7)

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• Do micromagnets expose spin qubits to charge and Johnson noise?
• Limits to Quantum Gate Fidelity from Near-Field Thermal and Vacuum Fluctuations
• Evanescent-wave Johnson Noise in small devices
• Anisotropy with respect to the applied magnetic field of spin qubit decoherence times
• Maximizing the purity of a qubit evolving in an anisotropic environment