Kim Y-S, Lee J-C, Kwon O, Kim Y-H. Protecting entanglement from decoherence using weak measurement and quantum measurement reversal. Nat Phys. 2012;8(2):117–20.
Abstract: Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death. Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing, quantum cryptography, quantum teleportation and quantum metrology. Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death.
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Saffman M. Quantum computing: A quantum telecom link. Nat Phys. 2010;6(11):838–9.
Abstract: Converting data-carrying photons to telecommunication wavelengths enables distribution of quantum information over long distances.
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Raussendorf R. Quantum computing: Shaking up ground states. Nat Phys. 2010;6(11):840–1.
Abstract: Measurement-based quantum computation with an Affleck-Kennedy-Lieb-Tasaki state is experimentally realized for the first time.
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Grinolds MS, Maletinsky P, Hong S, Lukin MD, Walsworth RL, Yacoby A. Quantum control of proximal spins using nanoscale magnetic resonance imaging. Nat Phys. 2011;7(9):687–92.
Abstract: Quantum control of individual spins in condensed-matter systems is an emerging field with wide-ranging applications in spintronics, quantum computation and sensitive magnetometry. Recent experiments have demonstrated the ability to address and manipulate single electron spins through either optical or electrical techniques. However, it is a challenge to extend individual-spin control to nanometre-scale multi-electron systems, as individual spins are often irresolvable with existing methods. Here we demonstrate that coherent individual-spin control can be achieved with few- nanometre resolution for proximal electron spins by carrying out single-spin magnetic resonance imaging (MRI), which is realized using a scanning-magnetic-field gradient that is both strong enough to achieve nanometre spatial resolution and sufficiently stable for coherent spin manipulations. We apply this scanning-field-gradient MRI technique to electronic spins in nitrogen-vacancy (NV) centres in diamond and achieve nanometre resolution in imaging, characterization and manipulation of individual spins. For NV centres, our results in individual-spin control demonstrate an improvement of nearly two orders of magnitude in spatial resolution when compared with conventional optical diffraction-limited techniques. This scanning-field-gradient microscope enables a wide range of applications including materials characterization, spin entanglement and nanoscale magnetometry.
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Hollenberg LCL. Quantum control: Through the quantum chicane. Nat Phys. 2012;8(2):113–4.
Abstract: In quantum control there is an inherent tension between high fidelity requirements and the need for speed to avoid decoherence. A direct comparison of quantum control protocols at these two extremes indicates where the sweet spot may lie.
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