Dc-powered Inelastic Cooper-pair Tunneling Amplifier Enables Quantum-Limited Gain

Quantum processors require rapid and accurate measurement of qubit states, a challenge that demands amplifiers capable of preserving the delicate quantum signals without adding excessive noise. Now, N. Nehra, N. Bourlet, A. H. Esmaeili, and colleagues demonstrate a groundbreaking new amplifier design that achieves near-perfect quantum performance with significantly reduced complexity. Their innovative device, an Inelastic Cooper-pair Tunneling Amplifier (ICTA), operates directly from a DC power source and delivers substantial gain across a wide range of microwave frequencies, approaching the theoretical limit of noise performance. This broadband ICTA eliminates the need for complex pump-tone systems commonly used in quantum amplification, promising a dramatic simplification of quantum processor hardware and paving the way for more scalable quantum computing.

It explains simulation details, presents experimental data, offers deeper insights into ICTA phenomena, and demonstrates the thoroughness of the research0.2 photons of the quantum limit. This breakthrough delivers 13 dB of average gain across a 3.5GHz bandwidth in a single stage, representing a significant advancement in quantum-limited amplification0.2 photons of the quantum limit using a DC-powered broadband amplifier0.5GHz bandwidth in a single stage. This eliminates the need for complex pump-tone infrastructure, promising significant reductions in hardware complexity, particularly for systems needing multiple amplification channels., Experiments demonstrate that the ICTA’s performance closely matches predictions from detailed semiclassical simulations, validating the design and enabling further optimization.

Measurements reveal an average added noise of less than 0.2 photons above the standard quantum limit, a crucial metric for preserving the integrity of quantum information. The team also measured the input-referred 1 dB compression point, finding an average value of −106 dBm across the 3.5GHz bandwidth. Further analysis revealed a correlation between cable length and gain structure, allowing for precise control and optimization of performance. The ICTA achieves this performance through a unique mechanism involving the tunneling of Cooper pairs and operates robustly near its designed operating point. This DC-powered design, combined with its high gain and low noise, promises to dramatically simplify quantum-limited amplification, particularly for applications requiring multiple channels, such as qubit readout in quantum processors.