Macroscopic resonant tunneling between the two lowest lying states of a bistable rf SQUID is used to characterize noise in a flux qubit. Measurements of the incoherent decay rate as a function of flux bias revealed a Gaussian-shaped profile that is not peaked at the resonance point but is shifted to a bias at which the initial well is higher than the target well. The rms amplitude of the noise, which is proportional to the dephasing rate 1/tauphi, was observed to be weakly dependent on temperature below 70 mK. Analysis of these results indicates that the dominant source of low energy flux noise in this device is a quantum mechanical environment in thermal equilibrium.

Abstract

We describe the fabrication and characterization of a nanoelectromechanical (NEM) switch based on carbon nanotubes. Our NEM structure consists of single-walled nanotubes (SWNTs) suspended over shallow trenches in a SiO(2) layer, with a Nb pull electrode beneath. The nanotube growth is done on-chip using a patterned Fe catalyst and a methane chemical vapor deposition (CVD) process at 850 degrees C. Electrical measurements of these devices show well-defined ON and OFF states as a dc bias up to a few volts is applied between the CNT and the Nb pull electrode. The CNT switches were measured to have speeds that are 3 orders of magnitude higher than MEMS-based electrostatically driven switches, with switching times down to a few nanoseconds, while at the same time requiring pull voltages less than 5 V.

An inkjet printed, biocompatible, heterostructure photodetector is described that was constructed using inks of photo-active molybdenum disulfide (MoS 2 ) and electrically conducting graphene which facilitated charge collection of the photocarriers. The importance of such devices stems from their potential utility in age-related-macular degeneration, which is a condition where the photosensitive retinal tissue degrades with aging, eventually compromising vision. The absence of effective therapeutic remedies for patients with this disorder has motivated the development of such devices to restore some degree of visual function. Inkjet printed, flexible prosthetic devices offer design simplicity where additive manufacturing can enable large format, low-cost arrays. The biocompatible inkjet printed two-dimensional heterojunction devices were photoresponsive to broadband incoming radiation in the visible regime, and the photocurrent I ph scaled proportionally with the incident light intensity, exhibiting a photoresponsivity R~0.30 A/W. This is 10 3 times higher compared to prior reports, and detectivity D was calculated to be~3.6 × 10 10 Jones. Straindependent measurements were also conducted with bending, indicating the feasibility of such devices printed on flexible substrates. Drop cast and printed CT-MoS 2 inks were characterized using techniques, such as Raman spectroscopy, photoluminescence measurements and scanning electron microscopy. Both mouse embryonic fibroblast and human esophageal fibroblast were used for the biocompatibility analysis for inks drop cast on two types of flexible substrates, polyethylene terephthalate and polyimide. The biocompatibility of inks formed using two-dimensional graphene and MoS 2 on polyimide substrates was extremely high, in excess of 98% for mouse embryonic fibroblast.