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Barreiro JT. Quantum physics: Environmental effects controlled. Nat Phys. 2011;7:927–928.
Abstract: An open quantum system loses its 'quantumness' when information about the state leaks into its surroundings. Researchers now show how this decoherence can be controlled between two incompatible regimes in the case of a single photon.
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Bozyigit D, Lang C, Steffen L, Fink JM, Eichler C, Baur M, et al. Antibunching of microwave-frequency photons observed in correlation measurements using linear detectors. Nat Phys. 2011;7(2):154–8.
Abstract: At optical frequencies the radiation produced by a source, such as a laser, a black body or a single-photon emitter, is frequently characterized by analysing the temporal correlations of emitted photons using single-photon counters. At microwave frequencies, however, there are no efficient single-photon counters yet. Instead, well-developed linear amplifiers allow for efficient measurement of the amplitude of an electromagnetic field. Here, we demonstrate first- and second-order correlation function measurements of a pulsed microwave-frequency single-photon source integrated on the same chip with a 50/50 beam splitter followed by linear amplifiers and quadrature amplitude detectors. We clearly observe single-photon coherence in first-order and photon antibunching in second-order correlation function measurements of the propagating fields.
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Mineev VP. Superfluid helium: Order in disorder. Nat Phys. 2012;8:253–254.
Abstract: Confining liquid 3He in porous silica aerogel prepared with strong anisotropy stabilizes a state of axial superfluidity.
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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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Haviland D. Superconducting circuits: Quantum phase slips. Nat Phys. 2010;6:565–566.
Abstract: Coulomb interactions can cause a rapid change in the phase of the wavefunction along a very narrow superconducting system. Such a phase slip at the quantum level is now measured in a chain of Josephson junctions.
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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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Home J. Quantum entanglement: Watching correlations disappear. Nat Phys. 2010;6(12):938–9.
Abstract: Engineered decoherence enables tracking of multipartite entanglement as a quantum state decays.
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Zhu J, Christensen J, Jung J, Martin-Moreno L, Yin X, Fok L, et al. A holey-structured metamaterial for acoustic deep-subwavelength imaging. Nat Phys. 2011;7(1):52–5.
Abstract: For classical waves such as light or sound, diffraction sets a natural limit on how finely the details of an object can be recorded on its image. Recently, various optical superlenses based on the metamaterials concept have shown the possibility of overcoming the diffraction limit. Similar two-dimensional (2D) acoustic hyperlens designs have also been explored. Here we demonstrate a 3D holey-structured metamaterial that achieves acoustic imaging down to a feature size of λ/50. The evanescent field components of a subwavelength object are efficiently transmitted through the structure as a result of their strong coupling with Fabry-Pérot resonances inside the holey plate. This capability of acoustic imaging at a very deep-subwavelength scale may open the door for a broad range of applications, including medical ultrasonography, underwater sonar and ultrasonic non-destructive evaluation.
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Zakka-Bajjani E, Nguyen Fçois, Lee M, Vale LR, Simmonds RW, Aumentado J. Quantum superposition of a single microwave photon in two different 'colour' states. Nat Phys. 2011;7(8):599–603.
Abstract: Fully controlled coherent coupling of arbitrary harmonic oscillators is an important tool for processing quantum information. Coupling between quantum harmonic oscillators has previously been demonstrated in several physical systems using a two-level system as a mediating element. Direct interaction at the quantum level has only recently been realized by means of resonant coupling between trapped ions. Here we implement a tunable direct coupling between the microwave harmonics of a superconducting resonator by means of parametric frequency conversion. We accomplish this by coupling the mode currents of two harmonics through a superconducting quantum interference device (SQUID) and modulating its flux at the difference (~7GHz) of the harmonic frequencies. We deterministically prepare a single-photon Fock state and coherently manipulate it between multiple modes, effectively controlling it in a superposition of two different 'colours'. This parametric interaction can be described as a beamsplitter-like operation that couples different frequency modes. As such, it could be used to implement linear optical quantum computing protocols on-chip.
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Lu C-Y, Zhou X-Q, Gühne O, Gao W-B, Zhang J, Yuan Z-S, et al. Experimental entanglement of six photons in graph states. Nat Phys. 2007;3(2):91–5.
Abstract: Graph states-multipartite entangled states that can be represented by mathematical graphs-are important resources for quantum computation, quantum error correction, studies of multiparticle entanglement and fundamental tests of non-locality and decoherence. Here, we demonstrate the experimental entanglement of six photons and engineering of multiqubit graph states. We have created two important examples of graph states, a six-photon Greenberger-Horne-Zeilinger state, the largest photonic Schrödinger cat so far, and a six-photon cluster state, a state-of-the-art `one-way quantum computer'. With small modifications, our method allows us, in principle, to create various further graph states, and therefore could open the way to experimental tests of, for example, quantum algorithms or loss- and fault-tolerant one-way quantum computation.
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