Probing single charge dynamics in solids can give insights into various quantum transport phenomena, most of which are fragile and short-time-scaled. Detection of these events in real-time requires a mesoscopic electrical amplifier with unprecedented sensitivity and operational bandwidth. In this work, we explore a hybrid electrical amplifier consisting of a semiconducting quantum point contact galvanically coupled to a superconducting λ/2 transmission-line resonator for ultra-fast and ultra-sensitive charge amplification. The resonator, made of aluminium with a coplanar waveguide geometry, is designed to operate at its first harmonic resonant mode ∼3.4GHz, where the reflected power from the resonator is amplitude-modulated by the conductance changes in the quantum point contact channel. From the sidebands of the amplitude modulated reflected signal we extract a conductance sensitivity of ). This sensitivity translates to a unit signal-to-noise measurement time ∼1.62ns for a variation of 0.01 ( in the conductance. From the analysis of the noise characteristics of the device, we find that up to a few MHz of signal frequency the sensitivity is limited by the photon assisted shot-noise associated with the electron tunnelling in the QPC channel. The optimization of various operational parameters of the device reveals a bandwidth of ∼155MHz which corresponds to a rise-time ∼2.2ns. Both the sensitivity and bandwidth that we obtain are greater by an order compared to the existing reports. In addition, the device also exhibits very good sensitivities up to a measurable frequency of 240MHz. The extremely high sensitivity, shot-noise limited detection, ultra-fast operation reaching the nanosecond time-scales, and the circuit QED architecture makes this scheme an attractive choice for single charge detection and counting experiments for spin-qubit readout and quantum electrical metrology.

探索固体中的单电荷动力学可以深入了解各种量子传输现象，其中大多数是脆弱的和短时间尺度的。实时检测这些事件需要具有前所未有的灵敏度和操作带宽的介观电放大器。在这项工作中，我们探索了一种混合电放大器，该放大器由与超导λ电流耦合的半导体量子点接触组成/2 传输线谐振器，用于超快速和超灵敏电荷放大。谐振器由铝制成，具有共面波导几何形状，设计为在其一次谐波谐振模式下工作~3.4GHz，其中来自谐振器的反射功率通过量子点接触通道中的电导变化进行幅度调制。从幅度调制反射信号的边带中，我们提取的电导灵敏度为 )。对于 0.01 (在电导中。通过对器件噪声特性的分析，我们发现在高达几 MHz 的信号频率时，灵敏度受到与 QPC 通道中电子隧穿相关的光子辅助散粒噪声的限制。器件各种操作参数的优化揭示了~155MHz 的带宽，对应于~2.2ns 的上升时间。与现有报告相比，我们获得的灵敏度和带宽都大了一个订单。此外，该设备还表现出非常好的灵敏度高达 240MHz 的可测量频率。极高的灵敏度、散粒噪声限制检测、达到纳秒时间尺度的超快操作以及电路 QED 架构使该方案成为自旋量子位读出和量子电计量的单电荷检测和计数实验的有吸引力的选择。