Preparation of Knill-Laflamme-Milburn states using tunable controlled phase gate

TL;DR

This paper proposes a method to generate Knill-Laflamme-Milburn states using a tunable controlled phase gate, optimizing the process in linear optics and extending it to arbitrary multi-qubit states.

Contribution

It introduces a novel scheme employing a tunable controlled phase gate for preparing KLM states, including an optimization and generalization to n-qubit states.

Findings

Successful scheme for two-qubit KLM state preparation

Optimized linear optics implementation

Generalization to arbitrary n-qubit KLM states

Abstract

A specific class of partially entangled states known as Knill-Laflamme-Milburn states (or KLM states) has been proved to be useful in relation to quantum information processing [Knill et al., Nature 409, 46 (2001)]. Although the usage of such states is widely investigated, considerably less effort has been invested into experimentally accessible preparation schemes. This paper discusses the possibility to employ a tunable controlled phase gate to generate an arbitrary Knill-Laflamme-Milburn state. In the first part, the idea of using the controlled phase gate is explained on the case of two-qubit KLM states. Optimization of the proposed scheme is then discussed for the framework of linear optics. Subsequent generalization of the scheme to arbitrary n-qubit KLM state is derived in the second part of this paper.