Cooling microwave fields into general multimode Gaussian states

TL;DR

This paper demonstrates how to use lossy, multi-chromatically modulated qubits to dissipatively engineer arbitrary multimode Gaussian states in bosonic systems, with potential applications in quantum computation.

Contribution

It introduces a method to generate any multimode Gaussian state using lossy qubits, extending previous single- and two-mode schemes to many modes in superconducting circuits.

Findings

Able to cool N modes into any Gaussian state

Successfully generated GHZ and cluster states

Method compatible with current superconducting technology

Abstract

We show that a collection of lossy multi-chromatically modulated qubits can be used to dissipatively engineer arbitrary Gaussian states of a set of bosonic modes. Our ideas are especially suited to superconducting-circuit architectures, where all the required ingredients are experimentally available. The generation of such multimode Gaussian states is necessary for many applications, most notably measurement-based quantum computation. We build upon some of our previous proposals, where we showed how to generate single-mode and two-mode squeezed states through cooling and lasing. Special care must be taken when extending these ideas to many bosonic modes, and we discuss here how to overcome all the limitations and hurdles that naturally appear. We illustrate our ideas with a fully worked out example consisting of GHZ states, but have also tested several other examples such as cluster states. All these examples allow us to show that it is possible to use a set of N lossy qubits to cool down a bosonic chain of N modes to any desired Gaussian state.