# Quantum teleportation of qudits by means of generalized quasi-Bell states of light

## TL;DR

This paper develops a theoretical framework for teleporting qudits encoded in superpositions of coherent states using generalized quasi-Bell states, achieving high fidelity and near-unit success probability with finite resources.

## Contribution

It introduces a new class of generalized quasi-Bell states for multicomponent Schr"odinger cat states and proposes a teleportation protocol with unit fidelity for qudits.

## Key findings

- Teleportation fidelity is unit for all input states.
- Success probability approaches unity with increasing photon number.
- Protocol is deterministic and resource-efficient.

## Abstract

Quantum superpositions of coherent states are produced both in microwave and optical domains, and are considered realizations of the famous "Schr\"odinger cat" state. The recent progress shows an increase in the number of components and the number of modes involved. Our work creates a theoretical framework for treatment of multicomponent two-mode Schr\"odinger cat states. We consider a class of single-mode states, which are superpositions of $N$ coherent states lying on a circle in the phase space. In this class we consider an orthonormal basis created by rotationally-invariant circular states (RICS). A two-mode extension of this basis is created by splitting a single-mode RICS on a balanced beam-splitter. We show that these states are generalizations of Bell states of two qubits to the case of $N$-level systems encoded into superpositions of coherent states on the circle, and we propose for them the name of generalized quasi-Bell states. We show that using a state of this class as a shared resource, one can teleport a superposition of coherent states on the circle (a qudit). Differently from some other existing protocols of quantum teleportation, the proposed protocol provides the unit fidelity for all input states of the qudit. We calculate the probability of success for this type of teleportation and show that it approaches unity for the average number of photons in one component above $N^2$. Thus, the teleportation protocol can be made unit-fidelity and deterministic at finite resources.