Minsu Kang

Generation of hybrid entanglement of light

Hyunseok Jeong, Alessandro Zavatta, Minsu Kang, Seung-Woo Lee, Luca S. Costanzo, Samuele Grandi, Timothy C. Ralph & Marco Bellini Center for Macroscopic Quantum Control, Department of Physics and Astronomy, Seoul National University, Seoul, 151-742, Korea Istituto Nazionale di Ottica (INO-CNR), L.go E. Fermi 6, 50125 Florence, Italy LENS and Department of Physics, University of Firenze, 50019 Sesto Fiorentino, Florence, Italy Centre for Quantum Computation and Communication Technology, School of Mathematics and Physics, University of Queensland, Qld 4072, Australia.

Characterizations and quantifications of macroscopic quantumness and its implementations using optical fields

Abstract We present a review and discussions on characterizations and quantifications of macroscopic quantum states as well as their implementations and applications in optical systems. We compare and criticize different measures proposed to define and quantify macroscopic quantum superpositions and extend such comparisons to several types of optical quantum states actively considered for experimental implementations within recent research topics.

Quantum macroscopicity measure for arbitrary spin systems and its application to quantum phase transitions

We explore a previously unknown connection between two important problems in physics, i.e., quantum macroscopicity and the quantum phase transition. We devise a general and computable measure of quantum macroscopicity that can be applied to arbitrary spin states. We find that a macroscopic quantum superposition of an extremely large size arises during the quantum phase transition of the transverse Ising model in contrast to some seeming macroscopic quantum phenomena such as superconductivity, superfluidity, and Bose-Einstein condensates. Our result may be an important step forward in understanding macroscopic quantum properties of many-body systems.

Experimental hybrid entanglement between quantum and classical states of light

The realization of hybrid entanglement between a microscopic (quantum) and a macroscopic (classical) system, in analogy to the situation of the famous Schrodingers cat paradox, is an important milestone, both from the fundamental perspective and for possible applications in the processing of quantum information. The most straightforward optical implementation of this condition is that of the entanglement between a single-photon and a coherent state. In this work, we describe the first step towards the generation of this type of hybrid entanglement from the experimental perspective.

Macroscopic entanglement in many-particle quantum states

We elucidate the relationship between Schrodinger-cat-like macroscopicity and geometric entanglement and argue that these quantities are not interchangeable. While both properties are lost due to decoherence, we show that macroscopicity is rare in uniform and in so-called random physical ensembles o...

Properties of hybrid entanglement between discrete- and continuous-variable states of light

We discuss some of the main features of a recently-generated form of hybrid entanglement between discrete- and continuous-variable states of light. Ideally, such a kind of entanglement should involve single-photon and coherent states as key representatives of the respective categories of states. Here we investigate the characteristics and limits of a scheme that, relying on a superposition of photon-creation operators onto two distinct modes, realizes the above ideal form of hybrid entanglement in an approximate way.

Production of entanglement with highly mixed states

We study production of entanglement with highly mixed states. We find that entanglement between highly mixed states can be generated via a direct unitary interaction even when both states have purities arbitrarily close to zero. This indicates that purity of a subsystem is not required for entanglement generation. This result is in contrast to previous studies where the importance of the subsystem purity was emphasized.