Featured
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Coherent electron–phonon coupling in tailored quantum systems
Graphene and InAs nanowires are both promising materials for coherent spin manipulation, but coupling between a quantum system and its environment leads to decoherence. Here, the contribution of electron–phonon coupling to decoherence in graphene and InAs nanowire is studied.
- P. Roulleau
- , S. Baer
- & T. Ihn
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| Open AccessMultimode quantum interference of photons in multiport integrated devices
Multimode interference devices could allow the implementation of multiport circuits for quantum technologies. Here, quantum interference is demonstrated in 2×2 and 4×4 multimode interference devices, and a technique is reported to characterize such devices.
- Alberto Peruzzo
- , Anthony Laing
- & Jeremy L. O'Brien
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Heisenberg-limited sensitivity with decoherence-enhanced measurements
Quantum-enhanced measurements use quantum mechanical effects to enhance measurement sensitivity of classical quantities; but the required quantum states are generally highly entangled and difficult to produce. In this study, the use of entangled states is avoided allowing Heisenberg-limited measurements.
- Daniel Braun
- & John Martin
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Quantum networks reveal quantum nonlocality
The nonlocality of a quantum state is often difficult to predict. Here, Cavalcanti and colleagues devise a method based on networks that makes this characterization much easier, revealing that the nonlocality of a quantum state depends on the context of the measurement.
- Daniel Cavalcanti
- , Mafalda L. Almeida
- & Antonio Acín
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Experimental magic state distillation for fault-tolerant quantum computing
Error correction in quantum computing can be implemented using transversal gates, which in turn rely on the availability of so-called magic states. The authors experimentally show that it is possible to improve the fidelity of these states by distilling five of them into one.
- Alexandre M. Souza
- , Jingfu Zhang
- & Raymond Laflamme
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Efficient quantum state tomography
Direct quantum state tomography—deducing the state of a system from measurements—is mostly unfeasible due to the exponential scaling of measurement number with system size. The authors present two new schemes, which scale linearly in this respect, and can be applied to a wide range of quantum states.
- Marcus Cramer
- , Martin B. Plenio
- & Yi-Kai Liu
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Macroscopically local correlations can violate information causality
Two principles have recently been proposed as attempts to provide physical axioms for quantum mechanics: causality and macroscopic locality. Cavalcanti and colleagues show here that the two are not equivalent, giving confidence in information causality as a constraint for correlations obtained in experiments.
- Daniel Cavalcanti
- , Alejo Salles
- & Valerio Scarani
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| Open AccessSingle-molecule identification via electric current noise
Molecular fluctuations are a source of noise that can impede single-molecule identification. Here, quantum-fluctuation-induced inelastic noise is observed as current fluctuations in individual molecules, suggesting that inelastic noise could be used as a molecular signature.
- Makusu Tsutsui
- , Masateru Taniguchi
- & Tomoji Kawai
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| Open AccessAll-linear time reversal by a dynamic artificial crystal
Signal processing by time reversal has thus far only been realized through nonlinear mechanisms. The authors describe an all-linear, and thus low-power, time-reversal process based on frequency inversion in a dynamically controlled artificial periodic structure, a dynamic magnonic crystal.
- Andrii V. Chumak
- , Vasil S. Tiberkevich
- & Burkard Hillebrands
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Review Article |
Quantum metrology for gravitational wave astronomy
Gravitational waves are predicted by general relativity, but their direct observation from astronomical sources hinges on large improvements in detection sensitivity. The authors review how squeezed light and other quantum optical concepts are being applied in the development of next generation interferometric detectors.
- Roman Schnabel
- , Nergis Mavalvala
- & Ping K. Lam
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| Open AccessAnisotropic structure of the order parameter in FeSe0.45Te0.55 revealed by angle-resolved specific heat
The structure of the superconducting gap of iron pnictide superconductors is controversial. In this paper, angle-resolved specific heat measurements are used to show that the gap is anisotropic, which is consistent with an extended s-wave model of superconducting pairing.
- B. Zeng
- , G. Mu
- & H.-H. Wen
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'Quantized' states of the charge-density wave in microcrystals of K0.3MoO3
In low-temperature one-dimensional metals, electrons condense into collective charge-density wave states. Zybtsevet al. observe conductivity jumps with temperature in a metal bar, as only specific wavelengths are permitted in the bar for the charge-density wave modes.
- S.G. Zybtsev
- , V.Ya. Pokrovskii
- & S.V. Zaitsev-Zotov
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No-go theorem for superradiant quantum phase transitions in cavity QED and counter-example in circuit QED
The authors show theoretically that in cavity quantum electrodynamics (QED), superradiant quantum phase transitions are forbidden. Conversely, for circuit QED, the quantum phase transition remains possible. This may pave the way for the study of interesting quantum phases.
- Pierre Nataf
- & Cristiano Ciuti
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Sustaining the Internet with hyperbolic mapping
Routing packets on the growing and changing underlying structure of the Internet is challenging and currently based only on local connectivity. Here, a global Internet map is devised: with a greedy forwarding algorithm, it is robust with respect to network growth, and allows speeds close to the theoretical best.
- Marián Boguñá
- , Fragkiskos Papadopoulos
- & Dmitri Krioukov
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Phase diagram of bismuth in the extreme quantum limit
Electrons in metals at extremely high magnetic fields show interesting quantum structures. The authors measure the angle-dependent Nernst effect with high precision and show that, for bismuth, Coulomb interactions between the electrons become important in this ultraquantum regime.
- Huan Yang
- , Benoît Fauqué
- & Kamran Behnia
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Magnetic flux lines in type-II superconductors and the 'hairy ball' theorem
The magnetic flux lines in a superconductor present intricate patterns, whose origins are seldom understood. Here the authors link them to geometrical effects by means of the 'hairy ball' theorem, which states that for a vector field on a sphere there will always be at least one singularity.
- Mark Laver
- & Edward. M. Forgan
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Experimental investigation of classical and quantum correlations under decoherence
Different types of correlations in quantum mechanical systems are crucial for quantum information processing. Xu and colleagues determine the sizes of classical correlations, entanglement and other types of quantum correlations in an optical setup.
- Jin-Shi Xu
- , Xiao-Ye Xu
- & Guang-Can Guo
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Mapping multiple photonic qubits into and out of one solid-state atomic ensemble
Quantum communication applications require memories capable of storing multiple qubits. To implement scalable architectures for this purpose, Usmani and coworkers turn to a rare-earth doped silicate, in which they demonstrate coherent and reversible mapping of 64 optical modes at the single photon level.
- Imam Usmani
- , Mikael Afzelius
- & Nicolas Gisin