Quantum physics articles within Nature Communications

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  • Article
    | Open Access

    The authors propose an implementation of Floquet non-Abelian topological insulators in a 1D three-band system with parity-time symmetry. Furthermore, they demonstrate that the bulk-edge correspondence is multifold and follows the multiplication rule of a quaternion group.

    • Tianyu Li
    •  & Haiping Hu

  • Article
    | Open Access

    Realising a quantum-backaction-limited oscillator in the acoustic frequency range would have applications in sensing and metrology. Here, the authors reach this goal by demonstrating destructive interference between quantum back-action noise and shot noise down to sub-kHz range in a warm atomic vapor cell.

    • Jun Jia
    • , Valeriy Novikov
    •  & Eugene S. Polzik

  • Article
    | Open Access

    Schrodinger’s cat states constitute an important resource for quantum information processing, but present challenges in terms of scalabilty and controllability. Here, the authors exploit fast Kerr nonlinearity modulation to generate and store cat states in superconducting circuits in a more scalable way.

    • X. L. He
    • , Yong Lu
    •  & Z. R. Lin

  • Article
    | Open Access

    Circuit QED with strongly driven cavities is a powerful framework for quantum technologies, but often undesired effects on the qubit are introduced. Here, by using an external tone tailored to destructively interfere with the cavity field, the authors show how a transmon can be protected from these unwanted effects.

    • Cristóbal Lledó
    • , Rémy Dassonneville
    •  & Alexandre Blais

  • Article
    | Open Access

    Nanodiamonds containing NV centers are promising electron paramagnetic resonance sensors, however applications are hindered by their random orientation. Qin et al. propose a new protocol that makes the technique insensitive to the sensor’s orientation and present a proof-of-principle in situ demonstration.

    • Zhuoyang Qin
    • , Zhecheng Wang
    •  & Jiangfeng Du

  • Article
    | Open Access

    Multiparameter sensors in quantum optics are often complex due to use of external fields. Here the authors demonstrate a simple single-shot all-optical vector atomic magnetometer based on machine learning for the correspondence of the measured signals and the magnetic field.

    • Xin Meng
    • , Youwei Zhang
    •  & Yanhong Xiao

  • Article
    | Open Access

    Our current understanding of the computational abilities of near-intermediate scale quantum (NISQ) computing devices is limited, in part due to the absence of a precise definition for this regime. Here, the authors formally define the NISQ realm and provide rigorous evidence that its capabilities are situated between the complexity classes BPP and BQP.

    • Sitan Chen
    • , Jordan Cotler
    •  & Jerry Li

  • Article
    | Open Access

    Performing quantum computing in the NISQ era requires reliable information on the gate noise characteristics and their performance benchmarks. Here, the authors show how to estimate the individual noise properties of any quantum process from the noisy eigenvalues of its corresponding quantum channel.

    • Yanwu Gu
    • , Wei-Feng Zhuang
    •  & Dong E. Liu

  • Article
    | Open Access

    Quantum theory allows for indefinite causal order, but experimental demonstrations of such scenarios have so far required trust in the internal functioning of the apparatus. Here, the authors point out a scenario where indefinite causal order could be certified in a device-independent way, if one excludes superluminal and retrocausal influences.

    • Tein van der Lugt
    • , Jonathan Barrett
    •  & Giulio Chiribella

  • Article
    | Open Access

    The beamsplitter operation is a key component for quantum information processing, but implementations in superconducting circuit-QED usually introduce additional decoherence. Here, the authors exploit the symmetry within a SQUID, driven in a purely differential manner, to realise clean BS operations between two SC cavity modes.

    • Yao Lu
    • , Aniket Maiti
    •  & Robert J. Schoelkopf

  • Article
    | Open Access

    Axions are hypothetical particles that constitute leading candidates for the identity of dark matter. Here, the authors improve previous exclusion bounds on axion-like particles in the range of 1.4–200 peV, and report direct terrestrial limits on the coupling of protons and neutrons with axion-like dark matter.

    • Itay M. Bloch
    • , Roy Shaham
    •  & Or Katz

  • Article
    | Open Access

    Quantum simulations of topological matter with superconducting qubits have been attracting attention recently. Xiang et al. realize 2D and bilayer Chern insulators with synthetic dimensions on a programmable 30-qubit-ladder superconducting processor, showing bulk-boundary correspondence.

    • Zhong-Cheng Xiang
    • , Kaixuan Huang
    •  & Heng Fan

  • Article
    | Open Access

    Rydberg atom arrays are a promising platform for simulating many-body systems. The authors introduce a tensor-network method to compute phase diagrams of infinite arrays with long-range interactions and experimental-scale finite arrays, unveiling a new entangled phase and offering a guide for experiments.

    • Matthew J. O’Rourke
    •  & Garnet Kin-Lic Chan

  • Article
    | Open Access

    By carefully inducing twists or lattice stacking offsets between two adjacent van der Waals crystals, a superlattice potential can be introduced. This Moire lattice offers an incredibly rich physics, ranging from superconductivity to exotic magnetism, depending on van der Waals materials in question. Here, Du et al. study the magnetic domains in twisted CrI3, and show that despite this domain structure, spin fluctuations are spatially homogenous.

    • Mengqi Huang
    • , Zeliang Sun
    •  & Chunhui Rita Du

  • Article
    | Open Access

    Security proofs against general attacks are the ultimate goal of QKD. Here, the authors show how the Generalised Entropy Accumulation Theorem can be used, for some classes of QKD scenarios, to translate security proofs against collective attacks in the asymptotic regime into proofs against general attacks in the finite-size regime.

    • Tony Metger
    •  & Renato Renner

  • Article
    | Open Access

    Negatively-charged boron vacancy centers in hBN have short coherence times, hindering their potential as quantum sensors. By employing dynamical decoupling, the authors achieve an ensemble coherence time approaching the fundamental relaxation limit, enabling sensitive detection of MHz range electromagnetic fields.

    • Roberto Rizzato
    • , Martin Schalk
    •  & Dominik B. Bucher

  • Article
    | Open Access

    In order to be practical, schemes for characterizing quantum operations should require the simplest possible gate sequences and measurements. Here, the authors show how random gate sequences and native measurements (followed by classical post-processing) are sufficient for estimating several gate set properties.

    • J. Helsen
    • , M. Ioannou
    •  & I. Roth

  • Article
    | Open Access

    Machine learning methods in condensed matter physics are an emerging tool for providing powerful analytical methods. Here, the authors demonstrate that convolutional neural networks can identify nematic electronic order from STM data of twisted double-layer graphene—even in the presence of heterostrain.

    • João Augusto Sobral
    • , Stefan Obernauer
    •  & Mathias S. Scheurer

  • Article
    | Open Access

    Testing general relativity with optical clocks is important both as a fundamental test and for metrological applications. Here, a vertical linear array of 5 separate ensembles of strontium atoms trapped in a single optical lattice is used to perform a blinded lab-based test of the gravitational redshift at the mm to cm scale.

    • Xin Zheng
    • , Jonathan Dolde
    •  & Shimon Kolkowitz

  • Article
    | Open Access

    Continuous-variable quantum networks are easier to implement than discrete-variable ones, but suffer from a lower teleportation fidelity. Here, the authors demonstrate a CV teleportation protocol exploiting heralded noiseless amplification to increase the fidelity, at the expense of probabilistic operation.

    • Jie Zhao
    • , Hao Jeng
    •  & Ping Koy Lam

  • Article
    | Open Access

    Hybrid quantum systems, such as superconducting qubits interacting with microwave photons in resonators, offer a rich platform for exploring fundamental physics. Wang et al. observe parity symmetry breaking in a probe qubit dispersively coupled to a resonator in the deep-strong coupling regime.

    • Shuai-Peng Wang
    • , Alessandro Ridolfo
    •  & J. Q. You

  • Article
    | Open Access

    The ability to perform nonlinear feedforward operations - that is, conditional operations controlled by nonlinear function of the measurement outcomes - is still a missing ingredient for measurement-based quantum computation. Here, the authors fill this gap using nonlinear electro-optical feedforward and non-Gaussian ancillary states.

    • Atsushi Sakaguchi
    • , Shunya Konno
    •  & Akira Furusawa

  • Article
    | Open Access

    It is often assumed that systems that can be analyzed accurately via mean-field theory would not be worth looking at using quantum algorithms, given entanglement plays no key role. Here, the authors show instead that a quantum advantage can be expected for simulating the exact time evolution of such electronic systems.

    • Ryan Babbush
    • , William J. Huggins
    •  & Joonho Lee

  • 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

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