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IEEE Transactions on Applied Superconductivity

Cryogenic Semiconductor Amplifier for RSFQ-Circuits With High Data Rates at 4.2 K

S. Wünsch, Thomas Ortlepp, E. Crocoll, Friedrich Uhlmann, M. Siegel

Published Jun 1, 2009• 16 citations
Publisher

Abstract

The connection of RSFQ circuits with commercial room temperature electronics and amplifying SFQ pulses with high data rates require cryogenic interface amplifiers. Such amplifiers should provide extremely high bandwidth, low noise and low power consumption at the same time. Various hybrid amplifiers based on commercial p-HEMT transistors in an embedded microwave design were designed and characterized. Towards the p-HEMT transistor characterization at cryogenic temperature the biasing settings according to an optimum between voltage gain and low power consumption were determined. Thus a total power consumption of 2 mW and a voltage gain of 12 dB per single stage were achieved. For a preamplifier and an amplifier concept a multiple number of these stages were implemented in a microstrip and a coplanar transmission line design with a special matched interconnect taper towards the RSFQ components. Measurements of the amplifiers, the combination of an amplifier with a RSFQ circuit at 4.2 K showed their good performances without any disturbance of the RSFQ circuit. Due to the losses between the stages a total gain of 25 dB with a four stage amplifier was achieved; pulse rates went up to 3 Gb/s. The total power consumption was in the range of 8 mW. Further increase of data rates will be achieved by improving the matching between RSFQ output stage and amplifier.

DOI
10.1109/tasc.2009.2018425

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The connection of RSFQ circuits with commercial room temperature electronics and amplifying SFQ pulses with high data rates require cryogenic interface amplifiers. Such amplifiers should provide extremely high bandwidth, low noise and low power consumption at the same time. Various hybrid amplifiers based on commercial p-HEMT transistors in an embedded microwave design were designed and characterized. Towards the p-HEMT transistor characterization at cryogenic temperature the biasing settings according to an optimum between voltage gain and low power consumption were determined. Thus a total power consumption of 2 mW and a voltage gain of 12 dB per single stage were achieved. For a preamplifier and an amplifier concept a multiple number of these stages were implemented in a microstrip and a coplanar transmission line design with a special matched interconnect taper towards the RSFQ components. Measurements of the amplifiers, the combination of an amplifier with a RSFQ circuit at 4.2 K showed their good performances without any disturbance of the RSFQ circuit. Due to the losses between the stages a total gain of 25 dB with a four stage amplifier was achieved; pulse rates went up to 3 Gb/s. The total power consumption was in the range of 8 mW. Further increase of data rates will be achieved by improving the matching between RSFQ output stage and amplifier.
There is a great deal of interest in amplifiers with extremely high bandwidth, low noise and low power consumption which interface RSFQ circuits with commercial room temperature electronics or amplifying SFQ pulses. In this special application a hybrid amplifier should interface an RSFQ circuitry with a Josephson junction array quantizer chip (JA-Q) at 4.2 K. The input signal for the amplifier is generated by an RSFQ signal generator and the output signal fed-in to a Josephson array quantizer. A voltage gain of about 10 4 with a pattern frequency of 2 GHz for a good transfer of the SFQ pulses is required. Additionally, the JA-Q requires a high output current at low power consumption of the amplifier at the same time. Various hybrid amplifiers based on commercially available p-HEMT transistors in an embedded microwave design were designed and characterized. For the p-HEMT transistor characterization at cryogenic temperatures the biasing settings according to an optimum between voltage gain A V and low power consumption P V were determined. Thus a power consumption of P V = 2 mW and a voltage gain of about A V = 4 per stage were achieved. For a preamplifier and an amplifier concept a number of these stages were implemented in a microstrip and a coplanar transmission line design with a special matched interconnect taper towards the RSFQ components. Measurements of the amplifiers and the combination of the amplifiers and the JA-Q at 4.2 K showed their good performance without any disturbances of the quantized voltage steps.
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The cryogenic indium phosphide (InP) high-electron-mobility transistor (HEMT) low-noise amplifier (LNA) is used for the readout amplification of qubits at444K where cooling capabilities are limited implying that the dc power of the active circuits is an essential design constraint. In this article, the RF and noise performance of the InP HEMT under ultralow-power (ULP) operation at444K has been characterized. The small-signal and noise parameter model of the InP HEMT was extracted down to 1μ\muμW. The tradeoff between noise performance and dc power consumption was analyzed in terms of the drain current and drain voltage. A 4–6 GHz hybrid cryogenic HEMT LNA designed for qubit readout and optimized for lowest noise below111mW dc power consumption was fabricated. The measured performance of the LNA at444K attained 23.1 dB average gain and 2.0 K average noise temperature at 200μ\muμW dc power.
A broadband low-noise four-stage high-electron-mobility transistor amplifier was designed and characterized in a cryogen-free dilution refrigerator at the 3.8 K temperature stage. The obtained power dissipation of the amplifier is below 20 mW. In the frequency range from 6 to 12 GHz its gain exceeds 30 dB. The equivalent noise temperature of the amplifier is below 6 K for the presented frequency range. The amplifier is applicable for any type of cryogenic microwave measurements. As an example we demonstrate here the characterization of the superconducting X-mon qubit coupled to an on-chip coplanar waveguide resonator.
We present a new kind of rapid-single-flux-quantum (RSFQ) output driver together with a pseudomorphic high electron mobility transistor (p-HEMT) amplifier both operating at liquid helium temperature. The passive interconnect including the interchip connection between the RSFQ output driver and the first transistor stage of the semiconductor amplifier is the key element for signal matching and was optimized for minimizing the reflections to the RSFQ circuit. The RSFQ output driver is based on a single-flux-quantum to dc converter and a voltage doubler. The circuit is realized in the Niobium based 1 kA/cm2process of FLUXONICS Foundry and provides up to 438-muV output voltage. We demonstrate high-speed experiments of the output driver in combination with two different semiconductor amplifier circuits at liquid helium temperature. The output voltage of a 2-Gb/s data stream was measured to be about 3.5 mV.
Large-scale superconducting quantum computers require massive numbers of high-performance cryogenic low-noise amplifiers (cryo-LNA) for qubit readout. Here we present a C-Band monolithic microwave integrated circuit (MMIC) cryo-LNA for this purpose. This cryo-LNA is based on 150 nm GaAs pseudomorphic high electron mobility transistor (pHEMT) process and implemented with a three-stage cascaded architecture, where the first stage adopts careful impedance match to optimize the noise and return loss. The integration of negative feedback loops adopted in the second and third-stage enhances the overall stability. Moreover, the pHEMT-self bias and current multiplexing circuitry structure facilitate the reduction of power consumption and require only single bias line. Operating at an ambient temperature of 3.6 K and consuming 15 mW, the cryo-LNA demonstrates good performance in the C-band, reaching a 5 K equivalent noise temperature and an average gain of 40 dB. We further benchmark this cryo-LNA with superconducting qubits, achieving an average single-shot dispersive readout fidelity of 98.3% without assistance from a quantum-limited parametric amplifier. The development of GaAs cryo-LNA diversifies technical support necessary for large-scale quantum applications.