We report an rf parametric amplifier that exploits the gate-tunable quantum capacitance of a semiconductor two-dimensional electron gas at cryogenic temperatures. The prototype amplifier exhibits a gain approximately 30 dB up to an input power of − 66 dBm and a noise temperature T N ∼ 2 K at approximately 370 MHz while dissipating approximately a microwatt of power. Operable at tesla-scale magnetic fields and temperatures ranging from millikelvin to a few kelvin, the quantum capacitance parametric amplifier may find utility in the readout circuit of spin qubits. Here, a quantum dot system is used to verify amplifier performance, improving the signal-to-noise ratio of the readout by approximately 9 dB.
We report an rf parametric amplifier that exploits the gate-tunable quantum capacitance of a semiconductor two-dimensional electron gas at cryogenic temperatures. The prototype amplifier exhibits a gain approximately 30 dB up to an input power of − 66 dBm and a noise temperature T N ∼ 2 K at approximately 370 MHz while dissipating approximately a microwatt of power. Operable at tesla-scale magnetic fields and temperatures ranging from millikelvin to a few kelvin, the quantum capacitance parametric amplifier may find utility in the readout circuit of spin qubits. Here, a quantum dot system is used to verify amplifier performance, improving the signal-to-noise ratio of the readout by approximately 9 dB.
We demonstrate a radio-frequency parametric amplifier that exploits the gate-tunable quantum capacitance of an ultra high mobility two dimensional electron gas (2DEG) in a GaAs heterostructure at cryogenic temperatures. The prototype narrowband amplifier exhibits a gain greater than 20 dB up to an input power of - 66 dBm (1 dB compression), and a noise temperature TN of 1.3 K at 370 MHz. In contrast to superconducting amplifiers, the quantum capacitance parametric amplifier (QCPA) is operable at tesla-scale magnetic fields and temperatures ranging from milli kelvin to a few kelvin. These attributes, together with its low power (microwatt) operation when compared to conventional transistor amplifiers, suggest the QCPA may find utility in enabling on-chip integrated readout circuits for semiconductor qubits or in the context of space transceivers and radio astronomy instruments.
Josephson parametric amplifiers (JPAs) approaching quantum-limited noise performance have been instrumental in enabling high fidelity readout of superconducting qubits and, recently, semiconductor quantum dots (QDs). We propose that the quantum capacitance arising in electronic two-level systems (the dual of Josephson inductance) can provide an alternative dissipation-less non-linear element for parametric amplification. We experimentally demonstrate phase-sensitive parametric amplification using a QD-reservoir electron transition in a CMOS nanowire split-gate transistor embedded in a 1.8~GHz superconducting lumped-element microwave cavity, achieving parametric gains of -3 to +3 dB, limited by Sisyphus dissipation. Using a semi-classical model, we find an optimised design within current technological capabilities could achieve gains and bandwidths comparable to JPAs, while providing complementary specifications with respect to integration in semiconductor platforms or operation at higher magnetic fields.
In microwave-based quantum circuits, including double quantum dots (DQDs), superconducting qubits and spin qubits, parametric amplifiers are indispensable in achieving high-fidelity qubit readouts. Despite its importance, the application of parametric amplifiers is hampered by several challenges, such as high insertion losses, constrained tunability, and a pronounced vulnerability to magnetic fields. Here, we demonstrate an on-site single-atom parametric amplifier (SAPA) within a reconfigurable quantum circuit, which consists of a superconducting microwave cavity and two GaAs gate-defined DQDs. Leveraging the inherent nonlinearity of the DQD, a parametric gain exceeding 11 dB is achieved. This gain contributes to enhance the qubit readout, as evidenced by exceeding two times improvement in the signal-to-noise ratio (SNR) when employing the DQD-based amplifier for reading out another DQD. Our work not only presents a versatile experimental platform with enhanced readout capabilities in quantum computing, but also introduces alternative choices of parametric amplifiers for a variety of microwave-based quantum circuits.
Josephson parametric amplifiers (JPAs) approaching quantum-limited noise performance have been instrumental in enabling high fidelity readout of superconducting qubits and, recently, semiconductor quantum dots (QDs). We propose that the quantum capacitance arising in electronic two-level systems (the dual of Josephson inductance) can provide an alternative dissipationless nonlinear element for parametric amplification. We experimentally demonstrate phase-sensitive parametric amplification using a QD-reservoir electron transition in a CMOS nanowire split-gate transistor embedded in a 1.8 GHz superconducting lumped-element microwave cavity, achieving parametric gains of -3 to +3 dB, limited by Sisyphus dissipation. Using a semiclassical model, we find an optimized design within current technological capabilities could achieve gains and bandwidths comparable to JPAs, while providing complementary specifications with respect to integration in semiconductor platforms or operation at higher magnetic fields.
Spins in semiconductor quantum dots hold great promise as building blocks of quantum processors. Trapping them in Si MOS transistorlike devices eases future industrial-scale fabrication. Among the potentially scalable readout solutions, gate-based dispersive radio-frequency reflectometry only requires the already existing transistor gates to read a quantum dot state, which alleviates the need for additional elements. In this effort toward scalability, traveling-wave superconducting parametric amplifiers significantly enhance the readout signal-to-noise ratio (SNR) by reducing the noise below that of typical cryogenic low-noise amplifiers, while offering a broad amplification band, essential to multiplex the readout of multiple resonators. In this work, we demonstrate a 3-GHz gate-based reflectometry readout of electron charge states trapped in quantum dots formed in Si MOS multigate devices, with SNR enhanced due to a Josephson traveling-wave parametric amplifier (JTWPA). The broad tunable 2-GHz amplification bandwidth combined with more than 10-dB ON-OFF SNR improvement of the JTWPA enables frequency and time-division-multiplexed readout of interdot transitions, and noise performance consistent with JTWPA characteristics at higher frequencies. In addition, owing to a design without superconducting loops and with a metallic ground plane, the JTWPA is flux insensitive and shows stable performance up to a magnetic field of 1.1 T at the quantum dot device, compatible with standard Si MOS spin-qubit experiments.
Spins in silicon quantum devices are promising candidates for large-scale quantum computing. Gate-based sensing of spin qubits offers a compact and scalable readout with high fidelity, however, further improvements in sensitivity are required to meet the fidelity thresholds and measurement timescales needed for the implementation of fast feedback in error correction protocols. Here, we combine radio-frequency gate-based sensing at 622 MHz with a Josephson parametric amplifier, that operates in the 500-800 MHz band, to reduce the integration time required to read the state of a silicon double quantum dot formed in a nanowire transistor. Based on our achieved signal-to-noise ratio, we estimate that singlet-triplet single-shot readout with an average fidelity of 99.7% could be performed in 1 μs, well below the requirements for fault-tolerant readout and 30 times faster than without the Josephson parametric amplifier. Additionally, the Josephson parametric amplifier allows operation at a lower radio-frequency power while maintaining identical signal-to-noise ratio. We determine a noise temperature of 200 mK with a contribution from the Josephson parametric amplifier (25%), cryogenic amplifier (25%) and the resonator (50%), showing routes to further increase the readout speed.