FIG. 1: (a) A double gate nanotube transistor embedded in the (4K) measuring scheme which includes bias resistors, DC blocks and a cryogenic low noise amplifier with a 200 : 50 Ohms matching transformer. The nanotube (colored in green), of diameter ∼ 2 nm, is covered in its middle part by a top gate (length 300 nm) which controls the local barrier. The leads on both sides act as electronic reservoirs. (b) The lumped element description of the nanotube transistor RF response includes the channel resistance g $_{−}$1 d , the transconductance g$_{m}$ , the gate capacitance C$_{g}$ = C$_{geo}$C$_{q}$/ ( C$_{geo}$ + C$_{q}$ ) with its geometrical (resp. quantum) contributions C$_{geo}$ (resp. C$_{q}$ ) and the noise current generator δi . The channel potential V$_{ch}$ = V$_{g}$ × C$_{g}$/C$_{q}$ governs the barrier height Φ = − e ( V$_{ch}$ + Const. ) which defines the gate coupling coefficient β = ∂ Φ /∂V$_{g}$ = C$_{g}$/C$_{q}$ . (c) Sketch of the energy profile (solid line) and the electronic distribution (blue gray scale) of a top-gated nanotube transistor. 8 V g V d 200  Ω 50 Ω G 4 : 1  (a) 4 nF 1 nF g d -1 V d V g V ch C geo /2 C q /2 C geo /2 C q /2 C g /2 -g m V g + δ i (b) (c) .eVd Source Drain gate nanotube oxide . Φ