Teleportation-Assisted Optical CSIGN Gates

TL;DR

This paper introduces two methods for implementing high-fidelity, near-deterministic controlled-sign-shift (CSIGN) gates using quantum teleportation techniques in linear optics, comparing their efficiency and resource use.

Contribution

It presents novel approaches for optical CSIGN gates via teleportation in both discrete and continuous variable regimes, achieving over 90% fidelity and near-deterministic operation.

Findings

Discrete-variable teleportation offers near-deterministic success with high fidelity.

Continuous-variable teleportation achieves over 90% fidelity despite finite squeezing.

Resource consumption varies significantly between the two approaches.

Abstract

Reliable entangling gates for qubits encoded in single-photon states represent a major challenge on the road to scalable quantum computing architectures based on linear optics. In this work, we present two approaches to develop high-fidelity, near-deterministic controlled-sign-shift gates based on the techniques of quantum gate teleportation. On the one hand, teleportation in a discrete-variable setting, i.e., for qubits, offers unit-fidelity operations but suffers from low success probabilities. Here, we apply recent results on advanced linear optical Bell measurements to reach a near-deterministic regime. On the other hand, in the setting of continuous variables, associated with coherent states, squeezing, and, typically, Gaussian states, teleportation can be performed in a deterministic fashion, but the finite amount of squeezing implies an inevitable deformation of a teleported single-mode state. Using a new generalized form of the nonlinear-sign-shift gate for gate teleportation, we are able to achieve fidelities of the resulting CSIGN gate above 90%. A special focus is also put on a comparison of the two approaches, not only with respect to fidelity and success probability, but also in terms of resource consumption.