A wideband radio-frequency amplifier for investigations at temperatures from 300 to 0.1 K

Abstract

A wideband cooled measuring amplifier, which solves a wide class of search problems in the area of cryoelectronics at frequencies of 10-100 MHz, is described. The amplifier differs from the existing prototypes in the reduced power consumption and influence on the source (suppressed back action effect), serviceability in a temperature interval of 0.1-300 K, and high regulated gain (up to 40 dB). The power consumed (dissipated) by the first ultralow-temperature stage, is ~1 μW. The circuitry components are commercially available.

An RF SQUID readout for a flux qubit-based microwave single photon counter

“…However, when the RF SQUID with parameters η a ≈ 3.5 × 10 11 V Wb −1 , L ≈ 240 pH, Ω P /2π ≈ 0.5 GHz, k 2 • Q ≈ 1, Q ≈ 300 is cooled down to temperatures of 10 − 15 mK, the intrinsic noise of the interferometer decreases proportionally to ∼T 2/3 , and the sensitivity estimate at the optimal operating point I RF = I opt (figure 5) leads to the values δε V ⩽ 10 −32 J Hz −1 . Note that the back-action effect of the resonator noise 'on the input' increases if the first stage of the amplifier and part of the resonator are at temperatures T T ≫ T, for example, in the temperature range 0.1-1 K. This emphasizes the importance of using a low DC power consumption HEMT amplifier [12][13][14] in the signal detection circuit located at temperature ∼30 mK.…”

“…T ≈ 30 mK is the effective resonator temperature which takes into account the noise impact of a two-stage ultra-low-power consumption HEMT amplifier [13,14]. The ratio of the resonator noise of equation ( 8) to the interferometer noise of equation ( 7) is…”

“…The first stage of the high-electron-mobility transistor (HEMT) amplifier with low DC power consumption (P DC ≈ 3 µW) at ultralow supply voltages in the unsaturated region of the static characteristic [13] and low brightness temperature [14] should be located at a temperature zone of the refrigerator with T ≈ 30 mK [15]. A cryogenic amplifier placed at 30 mK allows us to reduce the intrinsic noise of the resonator and improve the sensitivity of the RF SQUID.…”