Cryogenic amplifier with low input-referred voltage noise calibrated by shot noise measurement

A low-noise cryogenic amplifier for the bandwidth from 100 kHz to 2 MHz with commercially available components is presented. The amplifier is mounted on the cold finger of our home-made liquid helium dipstick. The input imp√edance of the amplifier is 2 k？. The input-referred voltage noise of the amplifier at approximately 2 MHz is around 1 n V/Hz^（1/2）. We demonstrate the performance of the amplifier by measuring shot noise on the Al/AlOx/Al tunneling junction with resistance about 17 k？ at liquid helium temperature.

Wideband cryogenic amplifier for a superconducting nanowire single-photon detector

We present a low-power inductorless wideband differential cryogenic amplifier using a 0.13-μm Si Ge Bi CMOS process for a superconducting nanowire single-photon detector(SNSPD).With a shunt-shunt feedback and capacitive coupling structure,theoretical analysis and simulations were undertaken,highlighting the relationship of the amplifier gain with the tunable design parameters of the circuit.In this way,the design and optimization flexibility can be increased,and a required gain can be achieved even without an accurate cryogenic device model.To realize a flat terminal impedance over the frequency of interest,an RC shunt compensation structure was employed,improving the amplifier’s closed-loop stability and suppressing the amplifier overshoot.The S-parameters and transient performance were measured at room temperature(300 K)and cryogenic temperature(4.2 K).With good input and output matching,the measurement results showed that the amplifier achieved a 21-d B gain with a 3-d B bandwidth of 1.13 GHz at 300 K.At 4.2 K,the gain of the amplifier can be tuned from 15 to 24 d B,achieving a 3-d B bandwidth spanning from 120 k Hz to 1.3 GHz and consuming only 3.1 m W.Excluding the chip pads,the amplifier chip core area was only about 0.073 mm^(2).

A 400 MHz Low Noise Amplifier at Cryogenic Temperature for Superconductor Filter System

A cryogenic low noise amplifier （LNA） using Agilent high electron mobility transistor （HEMT） for 380 MHzto 480 MHz is designed and fabricated, and the excellent cryogenic performance in superconducting receiver front-end for communication system is achieved. A special input impedance matching topology is implemented to provide low noise figure （NF） and good input matching in this cryogenic LNA design. The measurement results show that the NF is within 0.25 dB from the minimum NF of a single transistor, the power gain is above 20 dB, the flatness is within 1 dB, and the maximum input return loss is lower than -20 dB in bandwidth.

Squeezed state generation using cryogenic InP HEMT nonlinearity

This study focuses on generating and manipulating squeezed states with two external oscillators coupled by an InP HEMT operating at cryogenic temperatures.First,the small-signal nonlinear model of the transistor at high frequency at 5 K is analyzed using quantum theory,and the related Lagrangian is theoretically derived.Subsequently,the total quantum Hamiltonian of the system is derived using Legendre transformation.The Hamiltonian of the system includes linear and nonlinear terms by which the effects on the time evolution of the states are studied.The main result shows that the squeezed state can be generated owing to the transistor’s nonlinearity;more importantly,it can be manipulated by some specific terms introduced in the nonlinear Hamiltonian.In fact,the nonlinearity of the transistors induces some effects,such as capacitance,inductance,and second-order transconductance,by which the properties of the external oscillators are changed.These changes may lead to squeezing or manipulating the parameters related to squeezing in the oscillators.In addition,it is theoretically derived that the circuit can generate two-mode squeezing.Finally,second-order correlation(photon counting statistics)is studied,and the results demonstrate that the designed circuit exhibits antibunching,where the quadrature operator shows squeezing behavior.