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Taming Entanglement

Taming Entanglement

Taming Entanglement

Taming Entanglement

Taming Entanglement

Taming Entanglement

Taming Entanglement

Taming Entanglement

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TO APPEAR IN THE PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON QUAUNTUM COMMUNICATION,MEASUREMENT AND COMPUTING (QCMC 2002),BOSTON,MASSACHUSETTS,JULY 22-26,2002.TAMING ENTANGLEMENT PAUL KWIAT,JOE ALTEPETER,DAVID BRANNING,EVAN JEFFREY,NICHOLAS PETERS,AND TZU-CHIEH WEI Using a spontaneous parametric-downconversion source of photon pairs,we are working towards the creation of arbitrary 2-qubit quantum states with high fidelity.Currently,all physically allowable combinations of polarization entanglement and mixture can be produced,including maximally-entangled mixed states.The states are experimentally measured and refined via computer-automated quantum-state tomography,and this system has also been used to perform single-qubit and ancilla-assisted quantum process tomography.Central to the long-term future of quantum information processing is the capability of performing extremely accurate and reproducible gate opera-tions.The restrictions for fault-tolerant quantum computation are extremely demanding:the tolerable error-per-gate operation should be less than 10−4to 10−6.Implementing such precise gate operations and preparing the req-uisite input states is therefore one of the key milestones for quantum in-formation http://www.doczj.com/doc/5b17050879563c1ec5da71aa.html ing optical realizations of qubits,e.g.,polarization states of photons,we have the potential to meet these demanding tolerances.Therefore,although
large-scale quantum computers will perhaps never be con-structed solely using optical qubits,these systems nevertheless form a unique and convenient testbed with which to experimentally investigate the issues surrounding state creation,manipulation,and characterization,and also ways of dealing with decoherence.

TO APPEAR IN THE PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON QUAUNTUM COMMUNICATION,MEASUREMENT AND COMPUTING (QCMC 2002),BOSTON,MASSACHUSETTS,JULY 22-26,2002.TAMING ENTANGLEMENT PAUL KWIAT,JOE ALTEPETER,DAVID BRANNING,EVAN JEFFREY,NICHOLAS PETERS,AND TZU-CHIEH WEI Using a spontaneous parametric-downconversion source of photon pairs,we are working towards the creation of arbitrary 2-qubit quantum states with high fidelity.Currently,all physically allowable combinations of polarization entanglement and mixture can be produced,including maximally-entangled mixed states.The states are experimentally measured and refined via computer-automated quantum-state tomography,and this system has also been used to perform single-qubit and ancilla-assisted quantum process tomography.Central to the long-term future of quantum information processing is the capability of performing extremely accurate and reproducible gate opera-tions.The restrictions for fault-tolerant quantum computation are extremely demanding:the tolerable error-per-gate operation should be less than 10−4to 10−6.Implementing such precise gate operations and preparing the req-uisite input states is therefore one of the key milestones for quantum in-formation http://www.doczj.com/doc/5b17050879563c1ec5da71aa.html ing optical realizations of qubits,e.g.,polarization states of photons,we have the potential to meet these demanding tolerances.Therefore,although large-scale quantum computers will perhaps never be con-structed solely using optical qubits,these systems nevertheless form a unique and convenient testbed with which to experimentally investigate the issues surrounding state creation,manipulation,and characterization,and also ways of dealing with decoherence.

Figure 1.Spontaneous parametric downconversion.

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