TWPA
Crescendo-S

In superconducting quantum computing, Dispersion-Engineered Josephson Travelling Wave Parametric Amplifiers (J-TWPA) play a pivotal role in reading out qubit states. These states are stored in low-power radio frequency (RF) excitations. During readout, equally weak readout pulses are used which would drown in thermal noise at higher temperatures stages without proper amplification.

To achieve fast and high-fidelity readout of the qubit state, ultra-low-noise amplification is required close to the qubit at cryogenic temperatures. The J-TWPA stands as the state-of-the-art solution for this task.

J-TWPAs comprise a long chain of Josephson elements that facilitate a nonlinear wave mixing process which transfers power from a strong pump tone to the low-power signal. By carefully engineering its dispersion properties, this J-TWPA exponentially amplifies the readout signal along its length while adding close to the fundamental lower limit of added noise that results from Heisenberg uncertainty.

Contrary to Josephson Parametric Amplifiers (JPAs), J-TWPAs are transmissive rather than resonant devices, granting them a broad bandwidth unconstrained by resonator limitations. This enables the high degree of frequency multiplexing within a single readout chain that is paramount to scaling quantum computers towards advantage.