Quantum tetrachotomous states: Superposition of four coherent states on a line in phase space

TL;DR

This paper introduces quantum tetrachotomous states as superpositions of four distinguishable coherent states in phase space, analyzing their properties, creation methods, and potential realization in coupled-well systems, expanding the understanding of multichotomous quantum superpositions.

Contribution

The paper defines, characterizes, and proposes methods to create quantum tetrachotomous states, extending the concept of quantum superpositions beyond dichotomous states to four options.

Findings

QTS exhibit richer quantum phenomena than dichotomous states

Analysis of Wigner functions and photon-number distributions for QTS

Potential realization in coupled-well quantum systems

Abstract

The well studied quantum optical Schr\"{o}dinger cat state is a superposition of two distinguishable states, with quantum coherence between these macroscopically distinguishable states being of foundational and, in the context of quantum-information processing, practical use. We refer to these quantum-optical cat states as quantum dichotomous states, reflecting that the state is a superposition of two options, and we introduce the term quantum multichotomous state to refer to a superposition of multiple macroscopically distinguishable options. For a single degree of freedom, such as position, we construct the quantum multichotomous states as a superposition of Gaussian states on the position line in phase space. Using this nomenclature, a quantum tetrachotomous state (QTS) is a coherent superposition of four macroscopically distinguishable states. We define, analyze and show how to create such states, and our focus on the QTS is due to their exhibition of much richer phenomena than for the quantum dichotomous states with lessons to going to general multichotomous states with the quantum comb state as a limiting case. Our characterization of the QTS involves the Wigner function, its marginal distributions, and the photon-number distribution, and we discuss the QTS's approximate realization in a multiple coupled-well system.