Quantum physics articles within Nature Communications

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  • 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

  • Article
    | Open Access

    Light interaction with atoms depends on the strength of the light-matter coupling and the energy splitting of the modes involved. Here the authors study of quantum Rabi dynamics in a deep strong coupling regime by using a cloud of cold rubidium atoms.

    • Johannes Koch
    • , Geram R. Hunanyan
    •  & Martin Weitz

  • Article
    | Open Access

    Twin-field QKD should allow secure quantum communication with favourable rate-loss scaling, but requires interferometric implementations which are often impractical for long distances. Here, the authors show how to realise it without the need for closed interferometers.

    • Lai Zhou
    • , Jinping Lin
    •  & Zhiliang Yuan

  • Article
    | Open Access

    Fusion gates are common operations in photonic quantum information platforms, where they are employed to create entanglement. Here, the authors propose a quantum computation scheme where the same measurements used to generate entanglement can also be used to achieve fault-tolerance leading to an increased tolerance to errors.

    • Sara Bartolucci
    • , Patrick Birchall
    •  & Chris Sparrow

  • Article
    | Open Access

    The triangle causal structure represents a departure from the usual Bell scenario, as it should allow to violate classical predictions without the need for external inputs setting the measurement bases. Here the authors realise this scenario using a photonic setup with three independent photon sources.

    • Emanuele Polino
    • , Davide Poderini
    •  & Fabio Sciarrino

  • Article
    | Open Access

    Spins defined in single-walled carbon nanotubes promise ultra-long spin relaxation times, but qubit implementations require confinement of isolated spins. Here the authors report highly confined long-lived electron spins in chemically functionalized nanotubes and demonstrate their coherent control.

    • Jia-Shiang Chen
    • , Kasidet Jing Trerayapiwat
    •  & Xuedan Ma

  • Article
    | Open Access

    A possible route to scalability of trapped-ion-based quantum computing platforms is to connect multiple modules where ions can be shuttled across different registers. Here, the authors demonstrate fast and low-loss transfer of trapped ions between two microchip modules.

    • M. Akhtar
    • , F. Bonus
    •  & W. K. Hensinger

  • Article
    | Open Access

    Halide perovskites have a variety of attractive feature such as high quantum yield, and tunable optical properties, combined with easy fabrication. Here, Kirstein et al demonstrate spin-mode locking in CsPb(Cl0.56Br0.44)3 lead halide perovskite nanocrystals embedded in a fluorophosphate glass matrix, and a hole spin lifetime extending into the microsecond range.

    • E. Kirstein
    • , N. E. Kopteva
    •  & A. Greilich

  • Article
    | Open Access

    Rigorous results about the real computational advantages of quantum machine learning are few. Here, the authors prove that a PROMISEBQP-complete problem can be expressed by variational quantum classifiers and quantum support vector machines, meaning that a quantum advantage can be achieved for all ML classification problems that cannot be classically solved in polynomial time.

    • Jonas Jäger
    •  & Roman V. Krems

  • Article
    | Open Access

    Comparing the capabilities of different quantum machine learning protocols is difficult. Here, the authors show that different learning models based on parametrized quantum circuits can all be seen as quantum linear models, thus driving general conclusions on their resource requirements and capabilities.

    • Sofiene Jerbi
    • , Lukas J. Fiderer
    •  & Vedran Dunjko

  • Article
    | Open Access

    Electron spins in diamond allow magnetometry with high sensitivity, but the bandwidth in the microwave regime is limited to a narrow band around their resonance frequency. Here, the authors solve this problem by coupling the spins to a thin film of yttrium iron garnet, exploiting the non-linear spin-wave dynamics of the magnet.

    • Joris J. Carmiggelt
    • , Iacopo Bertelli
    •  & Toeno van der Sar

  • Article
    | Open Access

    Spin defects in 2D hBN are promising for magnetic field sensing but suffer from short spin coherence times. Here the authors extend the coherence time for an ensemble of spins in hBN to 4 microseconds by using a continuous microwave drive and demonstrate qubit control in a protected spin space.

    • Andrew J. Ramsay
    • , Reza Hekmati
    •  & Isaac J. Luxmoore

  • Article
    | Open Access

    Computational search for defect centers in semiconductors typically assumes that the defects realize the most thermodynamically stable configuration. Here the authors demonstrate, for a complex defect in silicon, that this is not always the case if the kinetics of defect formation is taken into account.

    • Peter Deák
    • , Péter Udvarhelyi
    •  & Adam Gali

  • Article
    | Open Access

    Quantum random number generators should ideally rely on few assumptions, have high enough generation rates, and be cost-effective and easy to operate. Here, the authors show an untrusted-homodyne-based MDI scheme that does not rely on i.i.d. assumption and is secure against quantum side information.

    • Chao Wang
    • , Ignatius William Primaatmaja
    •  & Charles Lim

  • Article
    | Open Access

    Studies on the fractional Schrödinger equation (FSE) remain mostly theoretical, due to the lack of materials supporting fractional dispersion or diffraction. Here, the authors indirectly realized the FSE using two programmable holograms acting as an optical Lévy waveguide.

    • Shilong Liu
    • , Yingwen Zhang
    •  & Ebrahim Karimi

  • Article
    | Open Access

    Characterisation of quantum hardware requires clear indications on what can and cannot be learned about quantum noise. Here, the authors show how to characterise learnable degrees of freedom of a Clifford gate using tools from algebraic graph theory.

    • Senrui Chen
    • , Yunchao Liu
    •  & Liang Jiang

  • Article
    | Open Access

    Quantifying communication capabilities produced by sharing an entangled qubit pair is still a subject of debate. Here the authors show that there are communication tasks for which sharing an entangled pair gives higher power than sharing two classical bits, even when there is no entanglement in the measurements.

    • Amélie Piveteau
    • , Jef Pauwels
    •  & Armin Tavakoli

  • Article
    | Open Access

    Ultracold ensembles are promising sources for precision measurements when their quantum state can precisely be prepared. Here the authors achieve a quantum state engineering of Bose-Einstein condensates in space using NASA’s Cold Atom Lab aboard the International Space Station making a step forward towards space quantum sensing.

    • Naceur Gaaloul
    • , Matthias Meister
    •  & Nicholas P. Bigelow

  • Article
    | Open Access

    Implementations of shallow quantum machine learning models are a promising application of near-term quantum computers, but rigorous results on their trainability are sparse. Here, the authors demonstrate settings where such models are untrainable.

    • Eric R. Anschuetz
    •  & Bobak T. Kiani

  • Article
    | Open Access

    Spin qubits in Si/SiGe quantum dots suffer from variability in the valley splitting which will hinder device scalability. Here, by using 3D atomic characterization, the authors explain this variability by random Si and Ge atomic fluctuations and propose a strategy to statistically enhance the valley splitting

    • Brian Paquelet Wuetz
    • , Merritt P. Losert
    •  & Giordano Scappucci

  • Article
    | Open Access

    Applications of ultra-low-loss photonic circuitry in quantum photonics, in particular including triggered single photon sources, are rare. Here, the authors show how InAs quantum dot single photon sources can be integrated onto wafer-scale, CMOS compatible ultra-low loss silicon nitride photonic circuits.

    • Ashish Chanana
    • , Hugo Larocque
    •  & Marcelo Davanco

  • Article
    | Open Access

    Renormalisation group methods serve for finding analytic solutions, critical points and computing phase diagrams of many-body systems. Here the authors demonstrate that renormalisation group schemes can be constructed for undecidable many-body systems, giving rise to the types of renormalisation group flow which are strictly more unpredictable than chaotic flows.

    • James D. Watson
    • , Emilio Onorati
    •  & Toby S. Cubitt

  • Article
    | Open Access

    Interaction-free measurements typically use repeated interrogations of an object that suppress the coherent evolution of the system. Dogra et al. demonstrate in a superconducting circuit a novel protocol that employs coherent repeated interrogations, and show that it yields a higher detection probability.

    • Shruti Dogra
    • , John J. McCord
    •  & Gheorghe Sorin Paraoanu

  • Article
    | Open Access

    The existing paradigms of system-bath control typically assume that the bath state is unchanged. By using spin defects in diamond, Dasari et al. demonstrate a scheme for controlling the state of the nuclear spin bath via selective measurements of the central qubit as a way of extending the qubit coherence time.

    • Durga Bhaktavatsala Rao Dasari
    • , Sen Yang
    •  & Jörg Wrachtrup

  • Article
    | Open Access

    Qutrits, or quantum three-level systems, can provide advantages over qubits in certain quantum information applications, and high-fidelity single-qutrit gates have been demonstrated. Goss et al. realize high-fidelity entangling gates between two superconducting qutrits that are universal for ternary computation.

    • Noah Goss
    • , Alexis Morvan
    •  & Irfan Siddiqi

  • Article
    | Open Access

    Getting a grip on the chaotic properties of quantum systems is difficult. Now, the effect of translational invariance in space in time in an ensemble of random quantum circuits is shown to lead to largely universal scaling laws describing the system without the need of knowing microscopic details.

    • Amos Chan
    • , Saumya Shivam
    •  & Andrea De Luca

  • Article
    | Open Access

    Quantum simulators allow for experimental studies of many-body systems in complex geometries, which has rarely been addressed by theory. Here the authors study many-body Hamiltonians on generic random graphs and show that many-body effects emerge only in a small class of exceptional, highly structured graphs.

    • Joseph Tindall
    • , Amy Searle
    •  & Dieter Jaksch

  • Article
    | Open Access

    Non-equilibrium quantum many-body systems undergoing repeated measurements exhibit phase transitions in their entanglement properties. Here the authors use a superconducting quantum simulator to demonstrate an entanglement phase transition that can be mapped to a vitrification transition in the spin glass theory.

    • Jeremy Côté
    •  & Stefanos Kourtis

  • Article
    | Open Access

    Exotic spin-dependent force are among the possible extensions of the Standard Model that can be probed by precision measurements. Here, the authors use a spin-exchange-relaxation free (SERF) K-Rb-21Ne comagnetometer to improve limits on spin- and velocity dependent forces.

    • Kai Wei
    • , Wei Ji
    •  & Dmitry Budker

  • Article
    | Open Access

    Breaking of Lorentz symmetry is related to the unification of fundamental forces and the extension of the standard model. Here the authors provide updated bounds on the Lorentz violation, by using measurements with trapped Yb+ ion, that represent an improvement over existing results.

    • Laura S. Dreissen
    • , Chih-Han Yeh
    •  & Tanja E. Mehlstäubler

  • Article
    | Open Access

    Quasiparticles, or broken Cooper pairs, are a major source of decoherence in superconducting qubits but their origin is debated. Pan et al. confirm the dominant mechanism due to photon absorption in the Josephson junction and demonstrate mitigation strategies based on tuning of the qubit geometry.

    • Xianchuang Pan
    • , Yuxuan Zhou
    •  & Dapeng Yu

  • Article
    | Open Access

    Storage of information, in any form, relies on patterns standing out from thermal fluctuations. In this work, the authors highlight a fundamental tradeoff quantifying the minimum amount of nonequilibrium resources needed to achieve a target level of accuracy in the processing of information.

    • Giulio Chiribella
    • , Fei Meng
    •  & Man-Hong Yung

  • Article
    | Open Access

    Quantum bath engineering in the context of circuit quantum electrodynamics typically relies on single-photon losses. Aiello et al. demonstrate an approach for engineering higher-order photon losses in a microwave resonator coupled to a tunnel junction, which may be utilized in quantum information applications.

    • Gianluca Aiello
    • , Mathieu Féchant
    •  & Jérôme Estève

  • Article
    | Open Access

    Hybrid quantum technologies synergistically combine different types of systems with complementary strengths. Here, the authors show monolithic integration and control of quantum dots and the emitted single photons in a surface acoustic wave-driven GaAs integrated quantum photonic circuit.

    • Dominik D. Bühler
    • , Matthias Weiß
    •  & Hubert J. Krenner

  • Article
    | Open Access

    Atoms and molecules under extreme temperature and pressure can be investigated using dense plasmas achieved by laser-driven implosion. Here the authors report spectral change of copper in billions atmosphere pressure that can only be explained by a self-consistent approach.

    • S. X. Hu
    • , David T. Bishel
    •  & Timothy Walton

  • Article
    | Open Access

    The effects of detection noise on quantum metrology performances have not been rigorously investigated yet. Here, the authors fill this gap by generalising the quantum Fisher information to the case of noisy readout, and showing the consequences the imperfect measurements bring.

    • Yink Loong Len
    • , Tuvia Gefen
    •  & Jan Kołodyński

  • Article
    | Open Access

    While transmon is the most widely used superconducting qubit, the search for alternative qubit designs with improved characteristic is ongoing. Hyyppä et al. demonstrate a novel superconducting qubit, the unimon, that combines high anharmonicity and protection against low-frequency charge noise and flux noise.

    • Eric Hyyppä
    • , Suman Kundu
    •  & Mikko Möttönen

  • Article
    | Open Access

    Atomically precise artificial lattices of dopant-based quantum dots offer a tunable platform for simulations of interacting fermionic models. By leveraging advances in fabrication and atomic-state control, Wang et al. report quantum simulations of the 2D Fermi-Hubbard model on a 3 × 3 few-dopant quantum dot array.

    • Xiqiao Wang
    • , Ehsan Khatami
    •  & Richard Silver

  • Article
    | Open Access

    A unified metric to assess the performances of quantum transducers, i.e., converters of quantum information between different physical systems - is still lacking. Here the authors propose quantum capacity as such metric, and use it to investigate the optimal designs of generic quantum transduction schemes.

    • Chiao-Hsuan Wang
    • , Fangxin Li
    •  & Liang Jiang

  • Article
    | Open Access

    Efficient protocols for comparing quantum states generated on different quantum computing platforms are becoming increasingly important. Zhu et al. demonstrate cross-platform verification using randomized measurements that allow for scaling to larger systems as compared to full quantum state tomography.

    • D. Zhu
    • , Z. P. Cian
    •  & C. Monroe

  • Article
    | Open Access

    Coherently interfacing microwave and optical radiation at the single photon level is an outstanding challenge in quantum technologies. Here, the authors show bi-directional on-chip conversion between MW and optical frequencies exploiting piezoelectric actuation of a gallium phosphide optomechanical resonator.

    • Robert Stockill
    • , Moritz Forsch
    •  & Simon Gröblacher

  • Article
    | Open Access

    High-energy particle impacts due to background or cosmic radiation have been identified as sources of correlated errors in superconducting qubit arrays. Iaia et al. achieve a suppression of correlated error rate by channeling the energy away from the qubits via a thick metal layer at the bottom of the chip.

    • V. Iaia
    • , J. Ku
    •  & B. L. T. Plourde

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