pling α and the inverse of the total capacitance of the resonator [22]. Recently, single-shot readout of the singlettriplet states in a double QD has been demonstrated with gate-based sensors, using a variety of resonator parameters to achieve a range of readout fidelities (for a given integration time): 73% (2.6 ms) [23], 82.9% (300 µs) [24], 98% (6 µs) [25] to 99% (1 ms; using ancillary 'sensor' QD and reservoir) [26].Amplifiers based on Josephson junctions have greatly improved signal-to-noise ratios (SNRs) in the field of superconducting circuits [27-32] -they typically operate at frequencies of several GHz and near the quantum limit of noise introduced by the amplifier (or indeed below, for a single quadrature using squeezing) [33][34][35][36][37][38]. Adopting such approaches in the measurement of QDs at RF/microwave frequencies is expected to lead to corresponding improvements in SNR. While this can in principle be achieved at operating frequencies of 4-8 GHz that are typical for Josephson-junction based amplifiers, as demonstrated using an InAs double QD, Josephson parametric amplifier (JPA) and coplanar waveguide resonator [39], lower frequency operation ( 1 GHz) becomes necessary [40] for studying lower QD tunneling rates, at which exchange interaction is more easily controlled, and for enabling off-chip resonator fabrication. Suitable amplifiers are available in such a frequency range, for example: a JPA operating at 600 MHz with a noise temperature of T JPA = 105 mK [41] or a SQUID amplifier chain with T SQUID = 52 mK at 538 MHz [42]. Building on such developments, readout of a GaAs based arXiv:1907.09429v2 [cond-mat.mes-hall]

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