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Dissipative binding of atoms by non-conservative forces
It is well known that chemical bonds are determined by potential minimum between two interacting atoms/molecules. Lemeshko and Weimer propose that a bond can also be induced by a dissipative process and further demonstrate this idea in a pair of ultracold caesium atoms trapped by a laser.
- Mikhail Lemeshko
- & Hendrik Weimer
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Complete tomography of a high-fidelity solid-state entangled spin–photon qubit pair
Future quantum communication technologies require entanglement between stationary and flying qubits, in systems that are inherently scalable. To this end, De Greveet al.present full state tomography of a qubit pair formed by entangling a quantum dot spin and a photon, with a fidelity of over 90%.
- Kristiaan De Greve
- , Peter L. McMahon
- & Yoshihisa Yamamoto
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Spatial entanglement of bosons in optical lattices
Estimating the entanglement in a system is vital for quantum information processing, particularly in many-body systems. To this end, Cramer et al.experimentally quantify multi-partite entanglement in an optical lattice across the superfluid-Mott insulator phase transition and at different temperatures.
- M. Cramer
- , A. Bernard
- & M.B. Plenio
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| Open AccessSemiclassical Monte-Carlo approach for modelling non-adiabatic dynamics in extended molecules
Many interesting chemical problems like photosynthesis and photovoltaics involve non-adiabatic dynamical phenomena, which are difficult to predict theoretically. Here, the authors develop a new numerical method capable of recovering quantum interferences that are neglected by conventional methods.
- Vyacheslav N. Gorshkov
- , Sergei Tretiak
- & Dmitry Mozyrsky
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Connection between Bell nonlocality and Bayesian game theory
A Bayesian game is one in which each player has incomplete information about all other players in the game. Nicolas Brunner and Noah Linden establish a direct connection between Bayesian games and the abstract theory of Bell nonlocality, which has a prominent role in quantum physics.
- Nicolas Brunner
- & Noah Linden
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Realistic loophole-free Bell test with atom–photon entanglement
A violation of Bell’s inequality would prove that a classical deterministic view of the universe is incorrect; however, despite long-standing efforts, irrefutable experimental proof of such a violation has yet to be produced. Teo et al. propose a realistic scenario that may finally overcome this challenge.
- C. Teo
- , M. Araújo
- & M. França Santos
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Engineering p-wave interactions in ultracold atoms using nanoplasmonic traps
Controlling p-wave interactions between fermions would enable studies of interesting quantum phenomena. Towards this end, Juliá-Díaz et al. propose a combination of strongly confined nanoplasmonic traps and laser-induced gauge fields that could produce the necessary coupling of atomic states.
- B. Juliá-Díaz
- , T. Graß
- & M. Lewenstein
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Experimental signature of programmable quantum annealing
Quantum annealing is the quantum computational equivalent of the classical approach to solving optimization problems known as simulated annealing. Boixo et al.report experimental evidence for the realization of quantum annealing processes that are unexpectedly robust against noise and imperfections.
- Sergio Boixo
- , Tameem Albash
- & Daniel A. Lidar
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Realistic control of network dynamics
Nonlinearity is a hallmark of complex networks, but has generally been regarded as an obstacle to controlling their behaviour. Here Cornelius et al.show how nonlinear dynamics can be harnessed to control a network and drive it to desired states.
- Sean P. Cornelius
- , William L. Kath
- & Adilson E. Motter
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Truly work-like work extraction via a single-shot analysis
Thermodynamics and information theory are closely related but the fundamental limitations of this relation are difficult to determine. Combining concepts from one-shot information theory, probability theory and statistical mechanics, the author quantifies extractable work in a non-equilibrium system.
- Johan Åberg
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Fundamental limitations for quantum and nanoscale thermodynamics
The usual laws of thermodynamics that are valid for macroscopic systems do not necessarily apply to the nanoscale, where quantum effects become important. Here, the authors develop a theoretical framework based on quantum information theory to properly treat thermodynamics at the nanoscale.
- Michał Horodecki
- & Jonathan Oppenheim
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Designing a practical high-fidelity long-time quantum memory
Future quantum computers need quantum memories that store arbitrary states for long periods, without incurring significant access latencies. Using high-order dynamical decoupling sequences, this work shows a practical scheme to suppress physical errors and guarantee high-fidelity storage for long times.
- Kaveh Khodjasteh
- , Jarrah Sastrawan
- & Lorenza Viola
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Magnetoelectric effects and valley-controlled spin quantum gates in transition metal dichalcogenide bilayers
Exploiting as many degrees of freedom of the electron as possible will make future electronic devices more versatile. Here, the authors show that coupling of spin, layer pseudospin and valley degrees of freedom in transition metal dichalcogenide bilayers makes them a promising platform for this purpose.
- Zhirui Gong
- , Gui-Bin Liu
- & Wang Yao
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Spin readout and addressability of phosphorus-donor clusters in silicon
The spin of an electron bound to a single phosphorus atom in silicon is of interest for spin-based electronics such as quantum computing. Here, Büch et al. show these spin properties are retained even for clusters of a few phosphorus atoms, providing an additional means for quantum bit addressability.
- H. Büch
- , S. Mahapatra
- & M. Y. Simmons
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Emergence of bimodality in controlling complex networks
The control of a complex network can be achieved by different combinations of relatively few driver nodes. Tao Jia and colleagues show that this can lead to two distinct control modes—centralized or distributed—that determine the number of nodes that can act as driver node.
- Tao Jia
- , Yang-Yu Liu
- & Albert-László Barabási
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Dynamical spin–orbital correlation in the frustrated magnet Ba3CuSb2O9
Spin–orbital quantum liquids are exotic quantum phases in frustrated magnets that arise if frustrated spin and orbital degrees of freedom are coupled. Here, the authors find a dynamical spin–orbital state in the frustrated magnet Ba3CuSb2O9, which indicates the formation of a spin–orbital quantum liquid.
- Yuki Ishiguro
- , Kenta Kimura
- & Yusuke Wakabayashi
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A scanning transmon qubit for strong coupling circuit quantum electrodynamics
Superconducting circuits may be useful as quantum simulators, but new tools are needed to fully characterize their behaviour. Shankset al.present a scanning transmon qubit, map its coupling strength to a separate resonator, and propose its use to probe photon number in a superconducting resonator lattice.
- W. E. Shanks
- , D. L. Underwood
- & A. A. Houck
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| Open AccessEngineering three-dimensional topological insulators in Rashba-type spin-orbit coupled heterostructures
Presently, the design of 3D topological insulators is limited to single-compound synthesis with appropriate symmetries. Here, the authors propose a new design principle for 3D topological insulators based on stacked 2D Fermi gases, which may allow for better control of topological properties.
- Tanmoy Das
- & A. V. Balatsky
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Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect
The spin Seebeck effect, which refers to a spin current induced by a temperature gradient, is experimentally well established but a comprehensive theoretical framework is still missing. Here the authors succeed in explaining the non-locality and in predicting a non-magnon origin of the effect.
- Konstantin S. Tikhonov
- , Jairo Sinova
- & Alexander M. Finkel’stein
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Thermally assisted quantum annealing of a 16-qubit problem
Quantum annealing is one strategy that may enable quantum computations that are robust to noise, despite the system’s interaction with the environment. Dickson et al. explore quantum annealing for a 16-qubit system and find that for a small energy-gap avoided crossing, it can be robust against thermal noise.
- N G Dickson
- , M W Johnson
- & G Rose
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Casimir forces on a silicon micromechanical chip
The Casimir effect is based on quantum electrodynamical effects between two electrically neutral objects in close proximity. Here Zou et al. observe the Casimir effect between two silicon components on a single micromechanical chip, allowing for an on-chip exploitation of the Casimir force.
- J. Zou
- , Z. Marcet
- & H. B. Chan
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| Open AccessControlled formation and reflection of a bright solitary matter-wave
Bright solitary waves in Bose–Einstein condensates are analogues of solitons in conventional wave systems, and may enable interesting tests of many-body quantum systems. Using 85Rb, Marchant et al.show the controlled formation of bright solitary matter-waves, and their reflection from a repulsive barrier.
- A. L. Marchant
- , T. P. Billam
- & S. L. Cornish
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Separation of neutral and charge modes in one-dimensional chiral edge channels
The Coulomb force between charges has a much greater influence on the electronic characteristics of 1D conductors than it does in 3D. Bocquillon et al. identify the separation of neutral and charged 1D edge modes, driven by Coulomb interactions in a quantum Hall system.
- E. Bocquillon
- , V. Freulon
- & G. Fève
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An information-theoretic principle implies that any discrete physical theory is classical
Quantum mechanics dictates that the act of obtaining information about a system must disturb the system. Pfister and Wehner show that if the converse is also true—that no information gain implies no disturbance—then state space can only be discrete if it is classical.
- Corsin Pfister
- & Stephanie Wehner
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A versatile source of single photons for quantum information processing
High-quality narrow bandwidth single-photon states with tunable frequency are essential for quantum and atomic technologies. Using a whispering gallery mode resonator, Förtsch et al. build such a source with wavelength tuning across 100 nm and controllable narrow bandwidth.
- Michael Förtsch
- , Josef U. Fürst
- & Christoph Marquardt
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| Open AccessTomonaga–Luttinger physics in electronic quantum circuits
When physicists study the characteristics of quantum conductors they usually take great pains to limit the resistance of other elements in the system. But Jezouin et al. show that when a single quantum channel is measured in series with a resistor, it exhibits analogous characteristics to a Tomonaga–Luttinger liquid.
- S. Jezouin
- , M. Albert
- & F. Pierre
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Evolution of Landau levels into edge states in graphene
It is difficult to observe the edge-bulk correspondence in two-dimensional electron systems, which display the quantum Hall effect. Here Li et al. follow the spatial evolution of Landau levels towards an edge of graphene by scanning tunnelling studies, revealing that the edge-bulk correspondence can be preserved.
- Guohong Li
- , Adina Luican-Mayer
- & Eva Y. Andrei
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Solid-state electronic spin coherence time approaching one second
Nitrogen-vacancy centres in diamond are a promising route for solid-state quantum information processing and magnetometry, but longer coherence times are needed to optimize protocols. Here, Bar-Gill et al. suppress decoherence to realize nitrogen-vacancy spin coherence times approaching one second.
- N. Bar-Gill
- , L.M. Pham
- & R.L. Walsworth
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| Open AccessTopological quantum computing with a very noisy network and local error rates approaching one percent
One approach to build a scalable quantum computer is to connect many smaller cells into a larger whole, but for realistic systems this quickly becomes prone to errors. Nickerson et al. present a noisy network protocol that can withstand high error rates within each cell but still perform stable purification.
- Naomi H. Nickerson
- , Ying Li
- & Simon C. Benjamin
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Efficient room-temperature nuclear spin hyperpolarization of a defect atom in a semiconductor
In order to use nuclear spins for the creation of qubits, an efficient nuclear spin hyperpolarisation at room temperature is crucial. Here the authors show how this can be achieved by spin polarized conduction-band electrons in a semiconductor, exploiting the defect-engineered spin-filtering effect.
- Y. Puttisong
- , X.J. Wang
- & W.M. Chen
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Theory of quantum oscillations in the vortex-liquid state of high-Tc superconductors
Quantum oscillations in the underdoped cuprate superconductors suggest the existence of a continuous Fermi surface, but specific heat measurements in strong magnetic fields suggest singular behaviour characteristic of point nodes. Banerjee et al. show how a vortex-liquid state could resolve this dichotomy.
- Sumilan Banerjee
- , Shizhong Zhang
- & Mohit Randeria
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A violation of the uncertainty principle implies a violation of the second law of thermodynamics
The laws of thermodynamics and of quantum mechanics are usually derived within different theoretical frameworks. But, Haenggi and Wehner show they are intimately related, such that a violation of quantum uncertainty would allow a heat cycle with a net work gain, violating the second law of thermodynamics.
- Esther Hänggi
- & Stephanie Wehner
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| Open AccessQuantum engineering at the silicon surface using dangling bonds
The ability to add and move individual atoms on a surface with a scanning tunnelling microscope enables precise control over the electronic quantum states of the surface. Schofield et al. show that removing hydrogen atoms from a passivated silicon surface can be used to generate and control such states.
- S. R. Schofield
- , P. Studer
- & D. R. Bowler
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| Open AccessQuantum coherence controls the charge separation in a prototypical artificial light-harvesting system
In artificial photosynthetic devices, conversion of light into electricity is thought to involve an incoherent electron transfer process. Rozzi et al.provide evidence for quantum-correlated wavelike motion inducing the ultrafast photoinduced electronic charge transfer in a light-harvesting supramolecular triad.
- Carlo Andrea Rozzi
- , Sarah Maria Falke
- & Christoph Lienau
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Controlling colloidal phase transitions with critical Casimir forces
Colloids consist of small particles distributed in another medium such as liquids or gases. Here, the demonstration that forces arising from the critical Casimir effect can control the interaction between particles offers new possibilities for the formation of colloidal nanostructures.
- Van Duc Nguyen
- , Suzanne Faber
- & Peter Schall
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Topologically protected quantum state transfer in a chiral spin liquid
Most quantum technologies rely upon quantum wires to ensure the faithful transfer of quantum states between remote locations—a process that is especially vulnerable to decoherence. Yao et al.propose a means to harness topological protection to design a quantum wire that is intrinsically robust against decoherence.
- N.Y. Yao
- , C.R. Laumann
- & M.D. Lukin
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Topological states in a ladder-like optical lattice containing ultracold atoms in higher orbital bands
Arrays of ultracold gas atoms trapped in an optical lattice can mimic many of the behaviours of conventional matter and give rise to exotic quantum states of matter as well. Li et al. suggest that a system of atoms in a two-legged ladder-like lattice could exhibit topological insulator and topological superconductor states.
- Xiaopeng Li
- , Erhai Zhao
- & W. Vincent Liu
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Structural domain walls in polar hexagonal manganites
Domain walls in multiferroic materials exhibit novel properties that are not present in the bulk. This work reports first-principle calculations that relate the structure of the domain-wall to its electronic properties in multiferroic hexagonal manganites.
- Yu Kumagai
- & Nicola A. Spaldin
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Gated silicene as a tunable source of nearly 100% spin-polarized electrons
Silicene is a silicon-based analogue of graphene, but with subtle and potentially useful differences. Wei-Feng Tsai and colleagues show that these differences could be exploited to build electrically-gated silicene devices that generate and control spin-polarized currents with near perfect efficiency.
- Wei-Feng Tsai
- , Cheng-Yi Huang
- & A. Bansil
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| Open AccessUltrafast universal quantum control of a quantum-dot charge qubit using Landau–Zener–Stückelberg interference
Universal control of the state of qubits on timescales much shorter than the coherence time is necessary for quantum computation. The authors demonstrate electrical control of a charge qubit in quantum dots on the picosecond scale, which is orders of magnitude faster than previously reported.
- Gang Cao
- , Hai-Ou Li
- & Guo-Ping Guo
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Motional averaging in a superconducting qubit
One of the advantages that it is hoped quantum computers will have over classical computers is their ability to accurately simulate quantum phenomena. Silveri et al.take a step towards this goal by simulating so-called motional averaging in an artificial atom realized by a superconducting quantum bit.
- Jian Li
- , M.P. Silveri
- & G.S. Paraoanu
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Quantum-coupled radial-breathing oscillations in double-walled carbon nanotubes
Double-walled carbon nanotubes are a convenient system for studying quantum mechanical interactions in distinct but coupled nanostructures. Liu et al.characterize the coupling between radial-breathing mode oscillations of inner and outer walls of many double-walled nanotubes of different diameter and chirality.
- Kaihui Liu
- , Xiaoping Hong
- & Feng Wang
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| Open AccessUnraveling quantum pathways using optical 3D Fourier-transform spectroscopy
Knowledge of the Hamiltonian of a quantum system is essential for predicting and controlling its behaviour. Li et al.use optical three-dimensional Fourier-transform spectroscopy to separate and study each pathway, gaining quantitative insight into the quantum pathways of an atomic vapour Hamiltonian.
- Hebin Li
- , Alan D. Bristow
- & Steven T. Cundiff
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Exotic non-Abelian anyons from conventional fractional quantum Hall states
Non-Abelian anyons are exotic quasiparticles envisioned to be promising candidates for solid-state quantum computation. Clarkeet al. propose a device fabricated from fractional quantum Hall states and superconductors that supports a new type of non-Abelian defect that binds parafermionic zero modes.
- David J. Clarke
- , Jason Alicea
- & Kirill Shtengel
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Experimental implementation of bit commitment in the noisy-storage model
In quantum communication, the noisy-storage model assumes that an attacker’s memory device is imperfect, thus enabling two parties to implement protocols securely. Using polarization-entangled photon pairs, Ng et al.analyse and verify a two-party bit commitment protocol within the noisy-storage.
- Nelly Huei Ying Ng
- , Siddarth K. Joshi
- & Stephanie Wehner
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Quantum and classical confinement of resonant states in a trilayer graphene Fabry-Pérot interferometer
Multilayer graphene is a promising electronic material because of its tunable band structure and pseudospin properties. Campos et al.show giant conductance oscillations in a ballistic trilayer graphene Fabry-Pérot interferometer that can be suppressed both classically and quantum mechanically.
- L.C. Campos
- , A.F. Young
- & P. Jarillo-Herrero
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Experimental observation of quantum chaos in a beam of light
Chaotic dynamics can arise in quantum systems as well as classical ones, leading to its own interesting phenomena. Using an all-optical approach, Lemos et al. study the quantum-kicked harmonic oscillator and its nonlinear dynamics, controlling and mapping the transition into quantum chaotic behaviour.
- Gabriela B. Lemos
- , Rafael M. Gomes
- & Fabricio Toscano
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Level statistics of disordered spin-1/2 systems and materials with localized Cooper pairs
Quantum phase transitions are most commonly found to occur at zero temperature. Cuevaset al.present numerical evidence confirming that a quantum phase transition can also occur at finite temperature, provided strong disorder is present.
- Emilio Cuevas
- , Mikhail Feigel'man
- & Marc Mezard
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Quantum oscillations of nitrogen atoms in uranium nitride
Crystals containing atoms with widely disparate masses can exhibit unusual lattice dynamics. Using time-of-flight neutron scattering, Aczelet al. show that at high frequencies individual nitrogen atoms in uranium nitride behave as independent quantum harmonic oscillators.
- A.A. Aczel
- , G.E. Granroth
- & S.E. Nagler