New amplifier boosts weak radio signals for quantum computing

The performance of quantum computing readout chains is largely determined by their initial amplifier stage, demanding innovations in sensitivity and efficiency. Researchers have now developed a radio frequency parametric amplifier based on modulating the quantum capacitance of an ultrahigh mobility two-dimensional electron gas, offering a potential alternative to existing superconducting and semiconductor designs. These amplifiers use the fluctuation-dissipation theorem, focusing on superconductivity to achieve minimal noise levels. This new approach addresses limitations of current amplifiers, including restricted frequency operation and difficulty functioning in magnetic fields, while potentially bridging the gap between superconducting and semiconductor technologies. A variable quantum capacitance, achieved over a 10 millivolt range, forms the core of a new radio frequency parametric amplifier designed to boost weak signals critical for applications like quantum computing and radio astronomy. This capacitance, modulated by controlling electron density within a two-dimensional electron gas formed in a gallium arsenide/aluminum gallium arsenide heterostructure, acts as the bottom plate of a capacitor with a niobium titanium nitride gate layer as the top plate. The resulting device, termed a Quantum Capacitance Parametric Amplifier or QCPA, demonstrates gain through an increase in reflected signal power when activated, compared to…