Quantum physics articles within Nature Communications

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  • Article
    | Open Access

    Quantum annealing is usually discussed as a means of finding an optimal solution for a problem where there are many local minima, such as the travelling salesman. Here, Zhao et al present an intriguing example of quantum annealing in the case of the frustrated magnet α-CoV2O6, where a transverse magnetic field triggers the quantum annealing process.

    • Yuqian Zhao
    • , Zhaohua Ma
    •  & Yuesheng Li

  • Article
    | Open Access

    The authors experimentally study a chain of superconducting islands (SI) and quantum dots (QD), where a Bogoliubov quasiparticle occupies each SI. They demonstrate correlations between the quasiparticles in each SI mediated by a single spin on the QD, known as an “over-screened" doublet state of the QD.

    • Juan Carlos Estrada Saldaña
    • , Alexandros Vekris
    •  & Jesper Nygård

  • Article
    | Open Access

    Measuring quantum entanglement remains a demanding task. The authors introduce two functions to quantify entanglement induced by fermionic or bosonic statistics, in transport experiments. Both functions, in theory and experiment, are remarkably resilient against the nonuniversal effects of interactions.

    • Gu Zhang
    • , Changki Hong
    •  & Yuval Gefen

  • Article
    | Open Access

    Nearly a century after dark matter was proposed, yet its nature remains elusive. Here, authors present their dark photon dark matter search results using two atomic magnetometer arrays 1700 km apart in large magnetic shields and offer the strongest terrestrial constraint in this mass range to date.

    • Min Jiang
    • , Taizhou Hong
    •  & Jiangfeng Du

  • Article
    | Open Access

    The problem of reversibility within general quantum resource theories is still an open one. Here, the authors prove that a reversible entanglement manipulation framework (and, consequently, the concept of entanglement entropy) can be formally established by adjusting the setting to allow for probabilistic operations

    • Bartosz Regula
    •  & Ludovico Lami

  • Comment
    | Open Access

    Can many-body systems be beneficial to designing quantum technologies? We address this question by examining quantum engines, where recent studies indicate potential benefits through the harnessing of many-body effects, such as divergences close to phase transitions. However, open questions remain regarding their real-world applications.

    • Victor Mukherjee
    •  & Uma Divakaran

  • Article
    | Open Access

    Entangled local states can be made capable of violating Bell inequalities via nonlocality activation. Typical theoretical approaches require processing many copies of the original state and performing joint measurements on the ensemble. Here, instead, the authors experimentally demonstrate how to do so using a single copy of the state, broadcasting it to two spatially separated parties within a three-node network.

    • Luis Villegas-Aguilar
    • , Emanuele Polino
    •  & Geoff J. Pryde

  • Article
    | Open Access

    Interesting non-Hermitian quantum dynamics can be accessed in analogue quantum simulators consisting of Hermitian bosonic systems with squeezing and antisqueezing terms. Here, the authors use a coplanar waveguide resonator connected to a SQUID to simulate the bosonic version of the Kitaev chain.

    • Jamal H. Busnaina
    • , Zheng Shi
    •  & Christopher M. Wilson

  • Article
    | Open Access

    Parity detection is essential in quantum error correction. Here, authors propose a reliable joint parity measurement (JPM) scheme inspired by stimulated emission and experimentally implement the weight-2(4) JPM scheme in a tunable coupling superconducting circuit, which shows comparable performance to the standard CNOT-gate based scheme.

    • Sainan Huai
    • , Kunliang Bu
    •  & Yicong Zheng

  • Article
    | Open Access

    Solving combinatorial optimization problems using quantum or quantum-inspired machine learning models would benefit from strategies able to work with arbitrary objective functions. Here, the authors use the power of generative models to realise such a black-box solver, and show promising performances on some portfolio optimization examples.

    • Javier Alcazar
    • , Mohammad Ghazi Vakili
    •  & Alejandro Perdomo-Ortiz

  • Article
    | Open Access

    Usual multiqubit entangled states can be described using the graph formalism, where each edge connects only two qubits. Here, instead, the authors use a reprogrammable silicon photonics chip to showcase preparation, verification and processing of arbitrary four-qubit hypergraph states, where hyperedges describe entanglement within a subset of many qubits.

    • Jieshan Huang
    • , Xudong Li
    •  & Jianwei Wang

  • Article
    | Open Access

    Studying bounds on the speed of information propagation across interacting boson systems is notoriously difficult. Here, the authors find tight bounds for both the transport of boson particles and information propagation, for arbitrary time-dependent Bose-Hubbard-type Hamiltonians in arbitrary dimensions.

    • Tomotaka Kuwahara
    • , Tan Van Vu
    •  & Keiji Saito

  • Article
    | Open Access

    Manipulating quantum information encoded in a bosonic mode requires sizeable and controllable nonlinearities, but superconducting devices’ strong nonlinearities are normally static. Here, the authors use a SNAIL to suppress static nonlinearities and use drive-dependent ones to reach universal control of a bosonic mode.

    • Axel M. Eriksson
    • , Théo Sépulcre
    •  & Simone Gasparinetti

  • Article
    | Open Access

    Ensuring high-fidelity quantum gates while increasing the number of qubits poses a great challenge. Here the authors present a scalable strategy for optimizing frequency trajectories as a form of error mitigation on a 68-qubit superconducting quantum processor, demonstrating high single- and two-qubit gate fidelities.

    • Paul V. Klimov
    • , Andreas Bengtsson
    •  & Hartmut Neven

  • Article
    | Open Access

    Topological properties of a photonic environment are crucial to engineer robust photon-mediated interactions between quantum emitters. Here, the authors find general theorems on the topology of photon-mediated interactions, unveiling the phenomena of topological preservation and reversal.

    • Federico Roccati
    • , Miguel Bello
    •  & Angelo Carollo

  • Article
    | Open Access

    T centers in silicon are promising candidates for quantum applications yet suffer from weak optical transitions. Here, by integrating with a silicon nanocavity, the authors demonstrate an enhancement of the photon emission rate for a single T center.

    • Adam Johnston
    • , Ulises Felix-Rendon
    •  & Songtao Chen

  • Article
    | Open Access

    Strongly interacting interlayer excitons and the interplay between excitons and electronic states have recently been studied in moire superlattices. Here the authors study moire WS2/WSe2 heterobilayer with tuneable electron and exciton populations and find signatures of an excitonic Mott insulating state.

    • Beini Gao
    • , Daniel G. Suárez-Forero
    •  & Mohammad Hafezi

  • Article
    | Open Access

    Understanding machine learning models’ ability to extrapolate from training data to unseen data - known as generalisation - has recently undergone a paradigm shift, while a similar understanding for their quantum counterparts is still missing. Here, the authors show that uniform generalization bounds pessimistically estimate the performance of quantum machine learning models.

    • Elies Gil-Fuster
    • , Jens Eisert
    •  & Carlos Bravo-Prieto

  • Article
    | Open Access

    Interfacing single-photon emitters (SPEs) with high-finesse cavities can prevent decoherence processes, especially at elevated temperature, but its implementation remains challenging. Here, the authors report room-temperature strong coupling of SPEs in hexagonal boron nitride with a dielectric cavity based on bound states in the continuum, showing a Rabi splitting of ~ 4 meV.

    • T. Thu Ha Do
    • , Milad Nonahal
    •  & Son Tung Ha

  • Article
    | Open Access

    The ability to characterize large and complex nuclear-spin networks could enable quantum applications, such as quantum simulations of many-body physics. Here the authors develop a high-resolution quantum-sensing method and use it to image a network of 50 nuclear spins surrounding a single NV center in diamond.

    • G. L. van de Stolpe
    • , D. P. Kwiatkowski
    •  & T. H. Taminiau

  • Article
    | Open Access

    Studying out-of-equilibrium entanglement fluctuations is beyond the scope of current theories. Lim et al. present an analytical theory of fluctuations in long-time dynamics of entanglement in two classes of integrable lattice models, showing features reminiscent of universal mesoscopic fluctuations.

    • Lih-King Lim
    • , Cunzhong Lou
    •  & Chushun Tian

  • Article
    | Open Access

    Autonomous quantum error correction protects quantum systems against decoherence through engineered dissipation. Here the authors introduce the Star code, which actively corrects single-photon loss and passively suppresses low-frequency dephasing and implement it in a two-transmon device.

    • Ziqian Li
    • , Tanay Roy
    •  & David I. Schuster

  • Article
    | Open Access

    Real-time adaptive control of a qubit has been demonstrated but limited to single-axis Hamiltonian estimation. Here the authors implement two-axis control of a singlet-triplet spin qubit with two fluctuating Hamiltonian parameters, resulting in improved quality of coherent oscillations.

    • Fabrizio Berritta
    • , Torbjørn Rasmussen
    •  & Ferdinand Kuemmeth

  • Article
    | Open Access

    Detection of topological phases in experiments is challenging, especially in the presence of incoherent noise. Cong et al. introduce a novel method combining error correction and renormalization-group flow and apply it to characterization of quantum spin liquid phases realized in a Rydberg-atom simulator.

    • Iris Cong
    • , Nishad Maskara
    •  & Mikhail D. Lukin

  • Article
    | Open Access

    Qudits, higher-dimensional analogues of qubits, expand quantum state space for information processing using fewer physical units. Here the authors demonstrate control over a 16-dimensional Hilbert space, equivalent to four qubits, using combined electron-nuclear states of a single Sb donor atom in Si.

    • Irene Fernández de Fuentes
    • , Tim Botzem
    •  & Andrea Morello

  • Article
    | Open Access

    Electron charge and spin shuttling is a promising technique for connecting distant spin qubits. Here the authors use conveyor-mode shuttling to achieve high-fidelity transport of a single electron spin in Si/SiGe by separation and rejoining of two spin-entangled electrons across a shuttling distance of 560 nm.

    • Tom Struck
    • , Mats Volmer
    •  & Lars R. Schreiber

  • Article
    | Open Access

    R.-J. Slager et al. extend the theory of multigap topology from static to non-equilibrium systems. They identify Floquet-induced non-Abelian braiding, resulting in a phase characterized by anomalous Euler class, a multi-gap topological invariant. They also find a gapped anomalous Dirac string phase. Both phases have no static counterparts and exhibit distinct boundary signatures.

    • Robert-Jan Slager
    • , Adrien Bouhon
    •  & F. Nur Ünal

  • Article
    | Open Access

    By coupling a spin-qubit to a superconducting resonator, remote spin-entanglement becomes feasible. Here, Ungerer et al achieve strong coupling between a superconducting resonator and a singlet-triplet spin qubit, in an InAs nanowire.

    • J. H. Ungerer
    • , A. Pally
    •  & C. Schönenberger

  • Article
    | Open Access

    Trapped ion quantum systems based on sympathetic cooling use ions of different species. Here the authors demonstrate exchange cooling using two ions of the same species (40Ca+) by taking advantage of the exchange of energy when the ions are brought close together.

    • Spencer D. Fallek
    • , Vikram S. Sandhu
    •  & Kenton R. Brown

  • Article
    | Open Access

    Highly polarized nuclear spins can supress decoherence of electron spin qubits, but this requires near-unity polarization. Here the authors implement a protocol combining optical excitation and fast carrier tunnelling to achieve nuclear spin polarizations above 95% in GaAs quantum dots on a timescale of 1 minute.

    • Peter Millington-Hotze
    • , Harry E. Dyte
    •  & Evgeny A. Chekhovich

  • Article
    | Open Access

    Recent work proposed a machine learning algorithm for predicting ground state properties of quantum many-body systems that outperforms any non-learning classical algorithm but requires extensive training data. Lewis et al. present an improved algorithm with exponentially reduced training data requirements.

    • Laura Lewis
    • , Hsin-Yuan Huang
    •  & John Preskill

  • Article
    | Open Access

    The use of NISQ devices for useful quantum simulations of materials and chemistry is still mainly limited by the necessary circuit depth. Here, the authors propose to combine classically-generated effective Hamiltonians, hybrid fermion-to-qubit mapping and circuit optimisations to bring this requirement closer to experimental feasibility.

    • Laura Clinton
    • , Toby Cubitt
    •  & Evan Sheridan

  • Article
    | Open Access

    Thermal fluctuations can induce ordering in frustrated magnetic systems, yet the impact of quantum fluctuations is less explored. Here, in the controlled environment of a quantum annealer composed of superconducting qubits, the authors study a frustrated magnetic system finding that quantum fluctuations enhance magnetic correlations.

    • Alejandro Lopez-Bezanilla
    • , Andrew D. King
    •  & Avadh Saxena

  • Article
    | Open Access

    Light-matter interfaces implementing arbitrary conditional operations on incoming photons would have several applications in quantum computation and communications. Here, the authors demonstrate conditional polarization rotation induced by a single quantum dot spin embedded in an electrically contacted micropillar, spanning up to a pi flip.

    • E. Mehdi
    • , M. Gundín
    •  & L. Lanco

  • Article
    | Open Access

    Enhanced sensitivity is a key parameter in quantum metrology. Here the authors demonstrate a distributed quantum phase sensing method that uses fewer photons than the number of parameters needed, and an enhanced quantum sensitivity is achieved.

    • Dong-Hyun Kim
    • , Seongjin Hong
    •  & Hyang-Tag Lim

  • Article
    | Open Access

    The authors demonstrate a method controlling the lattice filling of doped 1D Bose-Hubbard system of Rb atoms composed of chains of 3 to 6 sites in an optical lattice. The control is achieved by changing of the light potential and interaction strength.

    • Andrea Di Carli
    • , Christopher Parsonage
    •  & Stefan Kuhr

  • Article
    | Open Access

    It is still unclear whether and how quantum computing might prove useful in solving known large-scale classical machine learning problems. Here, the authors show that variants of known quantum algorithms for solving differential equations can provide an advantage in solving some instances of stochastic gradient descent dynamics.

    • Junyu Liu
    • , Minzhao Liu
    •  & Liang Jiang

  • Article
    | Open Access

    Efficient characterisation of quantum many-body Hamiltonians has important applications for benchmarking NISQ devices. Here, the authors propose a method employing Chebyshev regression to learn the full Hamiltonian of a quantum system, with a sample complexity that scales efficiently with the system size.

    • Andi Gu
    • , Lukasz Cincio
    •  & Patrick J. Coles

  • Article
    | Open Access

    Learning Hamiltonians or Lindbladians of quantum systems from experimental data is important for characterization of interactions and noise processes in quantum devices. Here the authors propose an efficient protocol based on estimating time derivatives using multiple temporal sampling points and robust polynomial interpolation.

    • Daniel Stilck França
    • , Liubov A. Markovich
    •  & Johannes Borregaard

  • Article
    | Open Access

    Periodically driven quantum systems have been extensively studied but with a predominant focus on long-time dynamics. Here, the authors study short-to-intermediate-time dynamics of an isolated many-body system, showing that its response to driving is supressed for the initial state close to thermal equilibrium.

    • Lennart Dabelow
    •  & Peter Reimann

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