Squeezing and quantum state engineering with Josephson traveling wave amplifiers

TL;DR

This paper presents a quantum theory for Josephson traveling wave amplifiers, demonstrating their ability to generate nonclassical radiation, tailored squeezing spectra, and multi-mode entangled states for quantum computing applications.

Contribution

It introduces a comprehensive quantum model for Josephson traveling wave amplifiers, enabling tailored nonclassical state generation and advancing continuous variable quantum computing.

Findings

Device can generate broadband and discrete squeezing spectra.

Output can produce multi-mode entangled states for quantum computing.

The scheme scales favorably for microwave quantum information processing.

Abstract

We develop a quantum theory describing the input-output properties of Josephson traveling wave parametric amplifiers. This allows us to show how such a device can be used as a source of nonclassical radiation, and how dispersion engineering can be used to tailor gain profiles and squeezing spectra with attractive properties, ranging from genuinely broadband spectra to "squeezing combs" consisting of a number of discrete entangled quasimodes. The device's output field can be used to generate a multi-mode squeezed bath--a powerful resource for dissipative quantum state preparation. In particular, we show how it can be used to generate continuous variable cluster states that are universal for measurement based quantum computing. The favourable scaling properties of the preparation scheme makes it a promising path towards continuous variable quantum computing in the microwave regime.