A Schrodinger Cat Living in Two Boxes

TL;DR

This paper demonstrates the creation and full quantum state tomography of a two-mode Schrödinger cat state across two microwave cavities linked by a superconducting atom, advancing quantum information processing capabilities.

Contribution

It introduces a method to generate and characterize complex two-mode cat states in microwave cavities, enabling new avenues for fault-tolerant quantum computing.

Findings

Successful realization of a two-mode cat state in microwave cavities

Full quantum state tomography over a 100-dimensional Hilbert space

Potential for logical operations in quantum computation

Abstract

Quantum superpositions of distinct coherent states in a single-mode harmonic oscillator, known as "cat states", have been an elegant demonstration of Schrodinger's famous cat paradox. Here, we realize a two-mode cat state of electromagnetic fields in two microwave cavities bridged by a superconducting artificial atom, which can also be viewed as an entangled pair of single-cavity cat states. We present full quantum state tomography of this complex cat state over a Hilbert space exceeding 100 dimensions via quantum non-demolition measurements of the joint photon number parity. The ability to manipulate such multi-cavity quantum states paves the way for logical operations between redundantly encoded qubits for fault-tolerant quantum computation and communication.