Quantum Information with Continuous Variables

Philippe Grangier

Nicolas J. Cerf

Nicolas J. Cerf

Kuanshou Zhang, Jinxia Feng, Yuanji Li

Metropolitan fiber quantum communication network is the key step to construct quantum communication network. Owing to continuous variable (CV) quantum entangled states of optical field can be generated unconditionally and deterministically, high-performance quantum information processing with continuous variables based on quantum states of optical field can be achieved. However, quantum information processing with continuous variable over optical fiber is a great challenge.

Ulrik L. Andersen, Gerd Leuchs, Christine Silberhorn

Abstract Observables of quantum systems can possess either a discrete or a continuous spectrum. For example, upon measurements of the photon number of a light state, discrete outcomes will result whereas measurements of the light's quadrature amplitudes result in continuous outcomes. If one uses the continuous degree of freedom of a quantum system for encoding, processing or detecting information, one enters the field of continuous‐variable (CV) quantum information processing. In this paper we review the basic principles of CV quantum information processing with main focus on recent developments in the field. We will be addressing the three main stages of a quantum information system; the preparation stage where quantum information is encoded into CVs of coherent states and single‐photon states, the processing stage where CV information is manipulated to carry out a specified protocol and a detection stage where CV information is measured using homodyne detection or photon counting.

Nicolas J. Cerf, Gerd Leuchs, Eugene Simon Polzik

Quantum information describes the new field which bridges quantum physics and information science. The quantum world allows for completely new architectures and protocols. While originally formulated in continuous quantum variables, the field worked almost exclusively with discrete variables, such as single photons and photon pairs. The renaissance of continuous variables came with European research consortia such as ACQUIRE (Advanced Coherent Quantum Information Research) in the late 1990s, and QUICOV (Quantum Information with Continuous Variables) from 2000–2003. The encouraging research results of QUICOV and the new conference series CVQIP (Continuous Variable Quantum Information Processing) triggered the idea for this book.This book presents the state of the art of quantum information with continuous quantum variables. The individual chapters discuss results achieved in QUICOV and presented at the first five CVQIP conferences from 2002-2006. Many world-leading scientists working on continuous variables outside Europe also contribute to the book.