Quantum physics articles within Nature Communications

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  • Article
    | Open Access

    Experimental studies about the trainability and generalization capacities of quantum neural networks are highly in need. Here, the authors implement a previously proposed parametrization and training scheme using a 6-qubit superconducting quantum processor.

    • Xiaoxuan Pan
    • , Zhide Lu
    •  & Luyan Sun

  • Article
    | Open Access

    Single-shot readout of optically active spin qubits is typically limited by low photon collection rates and measurement back-action. Here the authors overcome these limitations by using an open cavity approach for single-shot readout of a semiconductor quantum dot and demonstrate record readout time of a few ns.

    • Nadia O. Antoniadis
    • , Mark R. Hogg
    •  & Richard J. Warburton

  • Article
    | Open Access

    Generalization - that is, the ability to extrapolate from training data to unseen data - is fundamental in machine learning, and thus also for quantum ML. Here, the authors show that QML algorithms are able to generalise the training they had on a specific distribution and learn over different distributions.

    • Matthias C. Caro
    • , Hsin-Yuan Huang
    •  & Zoë Holmes

  • Article
    | Open Access

    Hybrid quantum acoustic systems integrating qubits with phonons offer a novel platform for investigating open quantum systems. Kitzman et al. report control of superposition states of a transmon qubit under the effect of drive and dissipation by engineering its coupling to a bath of surface acoustic wave phonons.

    • J. M. Kitzman
    • , J. R. Lane
    •  & J. Pollanen

  • Article
    | Open Access

    The emergence of relaxation in unitarily evolving systems can be seen as a paradox, but not once the distinction between local and global dynamics is considered. Here, the authors use photons in an integrated optical interferometer to show that, for a system evolving unitarily on a global level, single-mode measurements converge to those of a thermal state.

    • F. H. B. Somhorst
    • , R. van der Meer
    •  & J. J. Renema

  • Article
    | Open Access

    There are different quantum algorithms developed for the security of current cryptographic concepts. Here the authors demonstrate a method to perform quantum-secured digital payments using unforgeable quantum cryptograms over an optical fiber link and verify the information-theoretic security.

    • Peter Schiansky
    • , Julia Kalb
    •  & Philip Walther

  • Article
    | Open Access

    As the size of quantum processors scales up, accurate characterization of errors due to various crosstalks between qubits becomes important. Here the authors use a novel benchmarking protocol to study single-gate fidelities in a 2x2 hole spin qubit array in germanium when qubits are driven simultaneously.

    • W. I. L. Lawrie
    • , M. Rimbach-Russ
    •  & M. Veldhorst

  • Article
    | Open Access

    Future single-photon-based quantum networks will require both reliable telecom single-photon sources and improvements in security analysis. Here, the authors show how to use quantum dots and difference frequency generation to perform long-distance QKD, also reducing secure key acquisition time thanks to improved analytical bounds.

    • Christopher L. Morrison
    • , Roberto G. Pousa
    •  & Alessandro Fedrizzi

  • Article
    | Open Access

    Variational approaches combined with machine learning are promising for solving quantum many-body problems, but they often suffer from scaling and optimization issues. Here the authors demonstrate that a stochastic representation of wavefunctions enables reducing the ground state search to standard regression.

    • Hristiana Atanasova
    • , Liam Bernheimer
    •  & Guy Cohen

  • Article
    | Open Access

    Understanding the structure of the Kondo cloud formed by conduction electrons screening the impurity spin is a long-standing problem in many-body physics. Shim et al. propose the spatial and energy structure of the multichannel Kondo cloud, by studying quantum entanglement between the impurity and the channels.

    • Jeongmin Shim
    • , Donghoon Kim
    •  & H.-S. Sim

  • Article
    | Open Access

    Removing excess energy (cooling) and reducing noise in superconducting quantum circuits is central to improved coherence. Lucas et al. demonstrate cooling of a superconducting resonator and its noisy environment to sub-mK temperatures by immersion in liquid 3He.

    • M. Lucas
    • , A. V. Danilov
    •  & S. E. de Graaf

  • Article
    | Open Access

    Out-of-time-ordered correlators of local operators can quantify information scrambling in quantum many-body systems, but they are not easily accessible in experiments. Here the authors show that their global versions can be used for the same purpose and has been measured in nuclear magnetic resonance experiments.

    • Tianci Zhou
    •  & Brian Swingle

  • Article
    | Open Access

    The boron vacancy center in hBN has been intensively studied, but its characterizations have remained limited. Here the authors achieve a 5-fold enhancement of coherence time using dynamical decoupling, which enables the direct estimation of defect concentration and its electric field susceptibility.

    • Ruotian Gong
    • , Guanghui He
    •  & Chong Zu

  • Article
    | Open Access

    Low-energy excitations of strongly correlated systems are described by the Tomonaga–Luttinger liquid theory. Here the authors employ Bragg spectroscopy to demonstrate a spin-incoherent Luttinger liquid in 6Li atoms using charge and spin excitations.

    • Danyel Cavazos-Cavazos
    • , Ruwan Senaratne
    •  & Randall G. Hulet

  • Article
    | Open Access

    Wigner molecules, or correlated localized electron states, has been reported in semiconductor quantum dots, but their interaction with environment has been less explored. Here the authors use the spin multiplet structure of a three-electron Wigner molecule to enhance and control dynamic nuclear polarization.

    • Wonjin Jang
    • , Jehyun Kim
    •  & Dohun Kim

  • Article
    | Open Access

    Measurement-induced phase transitions are notoriously difficult to observe. Here, the authors propose a neural-network-based method to map measurement outcomes to the state of reference qubits, allowing observation of the transition and extracting its critical exponents.

    • Hossein Dehghani
    • , Ali Lavasani
    •  & Michael J. Gullans

  • Article
    | Open Access

    Optically active defects in hBN are promising for quantum sensing and information applications, however, coherent control of a single defect has not been achieved so far. By using an efficient method to produce arrays of defects in hBN, Guo et al. isolate a new carbon-related defect and show its coherent control.

    • Nai-Jie Guo
    • , Song Li
    •  & Guang-Can Guo

  • Article
    | Open Access

    Classical mechanics predicts a bistability in the dynamics of the Duffing oscillator, a key model of nonlinear dynamics. By performing quantum simulations of the model, Chen et al. explain the bistability by quantum metastable states with long lifetimes and reveal a first-order dissipative phase transition.

    • Qi-Ming Chen
    • , Michael Fischer
    •  & Rudolf Gross

  • Article
    | Open Access

    In quantum technologies, scalable ways to characterise errors in quantum hardware are highly needed. Here, the authors propose an approximate version of quantum process tomography based on tensor network representations of the processes and data-driven optimisation.

    • Giacomo Torlai
    • , Christopher J. Wood
    •  & Leandro Aolita

  • Article
    | Open Access

    Interaction between localized electron spins and nuclear spins causes shifts in nuclear spin energy levels, but how this affects nuclear spin diffusion in quantum dots is not fully understood. Here the authors show that the central electron accelerates nuclear spin diffusion in GaAs/AlGaAs quantum dots.

    • Peter Millington-Hotze
    • , Santanu Manna
    •  & Evgeny A. Chekhovich

  • Article
    | Open Access

    Quantum technologies allow memory advantages in simulating stochastic processes, but a demonstration of this for non-Markovian processes (where the advantage would be stronger) has been missing so far. Here the authors fill this gap analytically and experimentally, using a single qubit memory to model non-Markovian processes.

    • Kang-Da Wu
    • , Chengran Yang
    •  & Thomas J. Elliott

  • Article
    | Open Access

    The authors present a method for super-resolution quantum microscopy at the Heisenberg limit by using pairs of entangled photons with balanced pathlengths. They improve the spatial resolution, imaging speed, and contrast-to-noise ratio in practice while providing a theoretical interpretation of the super-resolution feature.

    • Zhe He
    • , Yide Zhang
    •  & Lihong V. Wang

  • Article
    | Open Access

    Superconducting quantum simulators are promising platforms for simulations of quantum many-body systems. Here the authors simulate a periodically driven 1D quantum spin model hosting Majorana zero modes on a superconducting qubit processor and propose new protocols for their detection and braiding.

    • Nikhil Harle
    • , Oles Shtanko
    •  & Ramis Movassagh

  • Article
    | Open Access

    Encoding quantum information in qudits instead of qubits allows for several advantages, but scalable native entangling techniques would be needed. Here, the authors show how to use light-shift gates to perform entangling operations on trapped ion systems, with a calibration overhead which is independent on the qudit dimension.

    • Pavel Hrmo
    • , Benjamin Wilhelm
    •  & Martin Ringbauer

  • Article
    | Open Access

    The properties of edge states at the boundary between a quantum Hall insulator and a superconductor have recently been under scrutiny. Here, the authors find theoretically that Andreev reflection of an edge state is possible only if the superconductor is in the disordered limit, leading to stochastic edge state conductance and providing an explanation of a recent experiment.

    • Vladislav D. Kurilovich
    • , Zachary M. Raines
    •  & Leonid I. Glazman

  • Article
    | Open Access

    A measure of symmetry breaking in a quantum many-body system could provide insight into its dynamics. Ares et al. introduce a subsystem measure of symmetry breaking dubbed entanglement asymmetry and apply it to quantum quench dynamics in spin chains, revealing a quantum analogue of the Mpemba effect.

    • Filiberto Ares
    • , Sara Murciano
    •  & Pasquale Calabrese

  • Article
    | Open Access

    It has been predicted that entanglement phase diagrams of Haar-measure random states can show interesting phenomenology, including entanglement phase transitions. Here, the authors confirm these predictions using up to 15 qubits in a fully-connected superconducting quantum processor.

    • Tong Liu
    • , Shang Liu
    •  & Heng Fan

  • Article
    | Open Access

    The extent of problems in quantum chemistry for which quantum algorithms could provide a speedup is still unclear, as well as the kind of speedup one should expect. Here, the authors look at the problem of ground state energy estimation, and gather theoretical and numerical evidence for the fact that an exponential quantum advantage is unlikely for generic problems of interest.

    • Seunghoon Lee
    • , Joonho Lee
    •  & Garnet Kin-Lic Chan

  • Article
    | Open Access

    Usually, increasing the temperature of a system leads to disorder but supersolids can show the opposite trend. Here, the authors discuss the observation of a supersolid phase in a dilute gas of dysprosium atoms by increasing their temperature.

    • J. Sánchez-Baena
    • , C. Politi
    •  & T. Pohl

  • Article
    | Open Access

    Quantum-enhanced versions of weak coin flipping (a cryptographic primitive where two mistrustful parties agree on a random bit while favouring opposite outcomes) have been proposed in the past but never realised. Here, the authors fill this gap by improving on a previous proposal and implementing it with single photons in a fibre-based setup.

    • Simon Neves
    • , Verena Yacoub
    •  & Eleni Diamanti

  • Article
    | Open Access

    Authors model programmable photonic circuits targeting universal unitaries and verify that a type of unit rotation operator has a heavy-tailed distribution. They suggest hardware pruning for random unitary and present design strategies for high fidelity and energy efficiency in large-scale quantum computations and photonic deep learning accelerators.

    • Sunkyu Yu
    •  & Namkyoo Park

  • Article
    | Open Access

    Probing single rare earth ions is highly desirable for several quantum applications, but it is difficult due to low emission rates. Here, the authors demonstrate the detection and control of single Erbium ions emission using electro-optically active photonic crystal cavities patterned from thin-film lithium niobate.

    • Likai Yang
    • , Sihao Wang
    •  & Hong X. Tang

  • Article
    | Open Access

    Understanding phonon-induced relaxation in molecular qubits is a crucial step in realizing their application potential. Garlatti at al. use a combination of inelastic X-ray scattering and density functional theory to investigate the role of low-energy phonons on spin relaxation of a prototypical molecular qubit.

    • E. Garlatti
    • , A. Albino
    •  & S. Carretta

  • Article
    | Open Access

    Polarons are quasi-particles that emerge when impurity particle is mixed with the low-energy excitations of a medium. Here the authors study the case of atom-ion quantum mixtures and identify three separate bipolaronic regimes which can arise depending on the interaction range and strength.

    • Grigory E. Astrakharchik
    • , Luis A. Peña Ardila
    •  & Antonio Negretti

  • Article
    | Open Access

    Usually, observation of quantum interference in a non-local scenario (that is, when Alice’s measurement settings and Bob’s outcomes are space-like separated) relies on entanglement. Here, the authors experimentally show four-photon frustrated interference originating from the sources’ indistinguishability, without the need for entanglement.

    • Kaiyi Qian
    • , Kai Wang
    •  & Xiao-song Ma

  • Article
    | Open Access

    Quantum theory can describe scenarios with an indefinite causal order, but whether such processes could be witnessed in real scenarios by violating causal inequalities is still subject to debate. Here, the authors give an affirmative answer, showing that noncausal processes admit a description using the framework of time-delocalised subsystems.

    • Julian Wechs
    • , Cyril Branciard
    •  & Ognyan Oreshkov

  • Article
    | Open Access

    Previous demonstrations of quantum interference in solids have mainly been limited to intra-layer transport within single conductors. Zhu et al. report a new type of inter-layer quantum interference in graphene-based double-layer devices, due to interference between carrier diffusion paths across the constituent layers.

    • Lijun Zhu
    • , Xiaoqiang Liu
    •  & Changgan Zeng

  • Article
    | Open Access

    Previous demonstrations of electrically and optically detected magnetic resonance in OLED materials have established these systems as promising candidates for magnetic field sensing. Here the authors present an integrated OLED-based device for magnetic field imaging with sub-micron resolution.

    • Rugang Geng
    • , Adrian Mena
    •  & Dane R. McCamey

  • Article
    | Open Access

    Active field theories are powerful tools to explain phenomena such as motility-induced phase separation. The authors report an active analogue to the quantum mechanics tunneling effect, showing similarity to the Schrödinger equation, by introducing an extended model applicable to active particles with inertia.

    • Michael te Vrugt
    • , Tobias Frohoff-Hülsmann
    •  & Raphael Wittkowski

  • Article
    | Open Access

    Quantum sensors based on NV centers in diamond are well established, however the sensitivity of detection of high-frequency radio signals has been limited. Here the authors use nanoscale field-focusing to enhance sensitivity and demonstrate ranging for GHz radio signals in an interferometer set-up.

    • Xiang-Dong Chen
    • , En-Hui Wang
    •  & Fang-Wen Sun

  • Article
    | Open Access

    In quantum multiparameter estimation, achieving the best precision for each parameter is hindered by the Heisenberg principle. Here, the authors demonstrate how to mitigate this problem by using appropriate probe states.

    • Binke Xia
    • , Jingzheng Huang
    •  & Guihua Zeng

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