RAMBOQ

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Contract no.: IST-2001-38864Contract no.: IST-2001-38864

Coordinator:

J.G. RarityJ.G. Rarity

Abstract

We will explore the possibility of building scalable quantum information processors using novel ideas of linear quantum logic. This will include probabilistic CNOT gates assembled from single photon sources and sources of entangled states.

We will also investigate the development of higher dimensional quantum logic aimed at developing error

resilient quantum networks. Supporting work will develop more efficient detectors and practical single and multi-

photon sources suitable for logic realisations. A theoretical effort will aim to increase the efficiency of simple gates and look a scalability, error correction and the overall limits to

this technology.

Objectives RAMBOQ seeks to develop scalable quantum processors Robust optical links between quantum processors. Efficient quantum computation using conditional linear logic. Evaluate theoretical limits to conditional linear logic Reduce gate complexity and increase efficiency. Efficient creation of single photon input states, single mode entangled states and

efficient read out detectors. Single gate to cascaded (few gate) quantum logic. Novel quantum communication schemes: sharing/teleportation of quantum states Novel logic schemes using higher order states for multi-party quantum protocols.

2003 2004 2005

WP2 Input-output: Single/pair Photon Sources and Detectors

WP0 Management

WP1 Theory of linear quantum logic

WP3 Implementation of quantum logic.

WP4 Tools for Quantum Networks

WP5 Higher dimensional Hilbert spaces

WP6 Applications

six monthly meetings in WP0 feed through of theoretical support throughout the programme,feed out of sources and detectors to to WP3-5 during months 18-27 feed simple gate concepts to WP4/5 during months 12-24,

feed near term application ideas to WP6 in months 22-30.

Simplified Workplan

Partners

C P01 E & EE Department, Universityof Bristol, UK

UoB UK

P P02 Toshiba Research EuropeLimited, Cambridge, UK

TREL UK

P P03 Hewlett Packard EuropeanLaboratories, UK

HPLB UK

P P04 University of Queensland,Centre for Quantum ComputerTechnology, Australia

UQ AU

P P05 Group of Applied Physics,University of Geneva, Switz.

GAP Swiss

P P06 Institut FuerExperimentalphysik,Universitaet Wien, Austria

UNIVIE AT

P P07 Sektion Physik, Ludwig-Maximillians-Universität,Munchen,De

LMU DE

A to

P02P08 University of Cambridge,

Department of PhysicsCAM UK

A to

P07P09 Friedrich-Alexander-Universität

Erlangen-NürnbergFAU DE

A toP06 P10 Id Quantique, Geneva,

Switzerland.IDQ Swiss

P P11 THALES Research andTechnology

TRT FR

P P12 INFM/LONO at the Universityof Rome III

INFM/LONO

IT

P P13 Quantum Phenomena andMaterials, University of Paris 7

QPM FR

Original KLM gate, based on 2-mode interferometers.

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A compact twin photon source

Key features:• narrow spectral width• generation of entangled pairs of photons• coupling into fibers

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Main steps towards a twin photon source

• Modelisation Losses measurements (University Paris 7)

• Growth and processing (THALES)

• Surface emitting SHG and index measurements (University of Rome)

• Twin photon source charcaterisation Quantum optics experiments (University of Geneva)

MicroscopeObjective

Pum p Beam

DichroicMirror

Long-passFilter

Photon countingdetectors

2-D Scan table

L-B film containing dilute dyeCryostat

Confocal microscope for study of single dot emitters

Single photon interference: characterisation of single photon source

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We a k la se r O Rsing le p ho to nso urc e

Be a msp litte r

Sing lep ho to nd e te c to rs

C o inc id e nc eG a te

Requires a time bandwidth limited single photon source

Scalable gate?

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Sing le p ho to nso urc e

Pum pPDC

Pa rity g a te

C NO T g a te

Enta ng le dp a ir so urc e

Enc o d e

Enc o d e C o nfirm

C o nfirm

Destructive CNOT Using teleportation to make non-destructive gates

Higher order Hilbert Spaces

Pum pPDC Enta ng le d

p a ir so urc e

Ho lo g ra p hicEnc o d e

Ho lo g ra p hicEnc o d e

Ho lo g ra p icDe c o d e rs

Ho lo g ra p icDe c o d e rs

Will also be implemented in time bin entanglement scheme

Alice BobPulse

BBO

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a3

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Entanglement Purification

Key deliverables Simple experimentally achievable two qubit gate design M12 Prototype single photon source displaying quantum interference

M24 Novel pair photon sources for Q Logic applications M24 Demonstration of destructive CNOT function M12 Demonstration of entanglement purification, long distance

entanglement swapping and quantum telecloning M24 Demonstration of Byzantine agreement and multiparty secret

sharing M24 Review of applications of linear quantum logic, quantum networking

and higher Hilbert space encoding M36 Report on experiments to demonstrate scalable and cascadable

CNOT gates M36