From linear quantum system graphs to qubit graphs: Heralded generation of graph states

A graph picture of linear quantum systems (LQSs) is introduced in Quantum, 5:611 (2021) and arXiv:2211.04042 (2022) to provide systematic methods for generating multipartite genuine entanglement with and without postselection. An intriguing and pertinent question emerges from this approach: Can we find a shared structure between LQS graphs and qubit graphs, commonly referred to as graph states? If such a structure can be identified, it can be exploited to generate graph states with LQSs. Our work presents a partial but noteworthy answer to this question. Within this research, \emph{we suggest a directed graph structure, which enables the generation of arbitrary caterpillar graph states employing heralded schemes in LQSs}. The caterpillar graph states encompass various useful graph states for one-way quantum computing such as linear graphs, star graphs, and networks of star graphs. The states generated through this approach will serve as valuable resource states for arbitrary graph states with fusion gates.Comment: Comments are welcom

ABJM Amplitudes in U-gauge and a Soft Theorem

We report progress in computing and analyzing all tree amplitudes in ABJM theory. Inspired by the isomorphism between the orthogonal Grassmannian and the pure spinor geometries, we adopt a new gauge, called u-gauge, for evaluating the orthogonal Grassmannian integral for ABJM amplitudes. We carry out the integral explicitly for the 8-point amplitude and obtain the complete supersymmetric amplitude. The physical and spurious poles arise from the integral as expected from on-shell diagrams. We also derive a double scalar soft theorem of ABJM amplitudes and verify it for known amplitudes.Comment: 35 pages, 6 figures; v2. minor correction

Graph approach to entanglement generation by boson subtractions

Entanglement is at the heart of quantum information science in the fundamental and practical aspects. A priority for studying and utilizing entanglement is to find reliable procedures to generate entangled states. In this work, we propose a graph method to systematically search for schemes that obtains genuine entanglement in arbitrary $N$-partite boson systems without postselection. Our physical setup is based on the sculpting protocol, which converts the bosonic symmetrization into entanglement through an indeterministic $N$ boson subtraction operator. This protocol can be realized as heralded schemes of many-boson systems. We show that our graph picture of the sculpting protocol provides an organized strategy to find suitable sculpting protocols for various genuinely entangled states. We have found general schemes for qubit $N$-partite GHZ and W states which are much more efficient than former schemes with sculpting protocol. We also have found a qudit $N$-partite GHZ state generation scheme, which shows our approach provides a significantly powerful insight into finding simple solutions for complicated entangled states. As proof of concept that our theoretical schemes can be realized in many-boson systems, we propose a Bell state generation scheme in linear optical systems with polarization qubit encoding and heralded detections.Comment: REVTeX 4.2, 16 pages, comments are welcom

Quantum circuit simulation of linear optics using fermion to qubit encoding

This work proposes a digital quantum simulation protocol for the linear scattering process of bosons, which provides a simple extension to partially distinguishable boson cases. Our protocol is achieved by combining the boson-fermion correspondence relation and fermion to qubit encoding protocols. As a proof of concept, we designed quantum circuits for generating the Hong-Ou-Mandel dip by varying particle distinguishability. The circuits were verified with the classical and quantum simulations using the IBM Quantum and IonQ cloud services.Comment: 10 pages, 7 figure