Q-ESSENCE

Simulation of noise-assisted transport via optical cavity networks

Date: 
2011-01-11
Reference: 

Filippo Caruso, Nicolò Spagnolo, Chiara Vitelli, Fabio Sciarrino, and Martin B. Plenio
Phys. Rev. A 83, 013811 (2011)
http://link.aps.org/doi/10.1103/PhysRevA.83.013811

Efficient quantum state tomography

Date: 
2010-12-21
Author(s): 

Marcus Cramer, Martin B. Plenio, Steven T. Flammia, Rolando Somma, David Gross, Stephen D. Bartlett, Olivier Landon-Cardinal, David Poulin and Yi-Kai Liu

Reference: 

Nat. Commun. 1, 149 (2010)
doi:10.1038/ncomms1147

Quantum state tomography—deducing quantum states from measured data—is the gold standard for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger systems it becomes unfeasible because the number of measurements and the amount of computation required to process them grows exponentially in the system size. Here, we present two tomography schemes that scale much more favourably than direct tomography with system size.

Tensor Rank and Stochastic Entanglement Catalysis for Multipartite Pure States

Date: 
2010-11-08
Author(s): 

Lin Chen, Eric Chitambar, Runyao Duan, Zhengfeng Ji, and Andreas Winter

Reference: 

Phys. Rev. Lett. 105, 200501 (2010)

Quantum networks reveal quantum nonlocality

Date: 
2011-02-08
Author(s): 

Daniel Cavalcanti, Mafalda L. Almeida, Valerio Scarani and Antonio Acín

Reference: 

Nat. Commun. 2 , 184 (2011)
doi:10.1038/ncomms1193 (2011)

The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also a valuable resource for information-processing tasks, for example, quantum communication, quantum key distribution, quantum state estimation or randomness extraction. Still, deciding whether a quantum state is nonlocal remains a challenging problem.

Hybrid Long-Distance Entanglement Distribution Protocol

Date: 
2010-10-11
Author(s): 

J. B. Brask, I. Rigas, E. S. Polzik, U. L. Andersen, and A. S. Sørensen

Reference: 

Phys. Rev. Lett. 105, 160501 (2010)

We propose a hybrid (continuous-discrete variable) quantum repeater protocol for long-distance entanglement distribution. Starting from states created by single-photon detection, we show how entangled coherent state superpositions can be generated by means of homodyne detection. We show that near-deterministic entanglement swapping with such states is possible using only linear optics and homodyne detectors, and we evaluate the performance of our protocol combining these elements.

 

Giant Stark effect in the emission of single semiconductor quantum dots

Date: 
2010-07-19
Author(s): 

Anthony J. Bennett, Raj B. Patel, Joanna Skiba-Szymanska, Christine A. Nicoll, Ian Farrer, David A. Ritchie, and Andrew J. Shields

Reference: 

Appl. Phys. Lett. 97, 031104 (2010)

We study the quantum-confined Stark effect in single InAs/GaAs quantum dots embedded within a AlGaAs/GaAs/AlGaAs quantum well. By significantly increasing the barrier height we can observe emission from a dot at electric fields of 500 kV cm−1, leading to Stark shifts of up to 25 meV. Our results suggest this technique may enable future applications that require self-assembled dots with transitions at the same energy.

 

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