Qubits articles within Nature Communications

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  • Article
    | Open Access

    Readout of remote spins in quantum dot arrays is a challenge for future quantum computing architectures. Here, the authors implement electron cascade for spin readout on quantum dots far away from a charge sensor in a quadruple quantum dot device and discuss its applicability to large-scale arrays.

    • Cornelis J. van Diepen
    • , Tzu-Kan Hsiao
    •  & Lieven M. K. Vandersypen

  • Article
    | Open Access

    As quantum computing devices become more complex, they enter the realm of correlated noise, which is difficult to characterise and mitigate. Here, the authors demonstrate, over a range of superconducting devices, a method for non-Markovian dynamics characterisation based on the process tensor framework.

    • G. A. L. White
    • , C. D. Hill
    •  & K. Modi

  • Article
    | Open Access

    To design and manipulate qubits, it is necessary to engineer multidimensional non-equilibrium steady states immune to decoherence in an open system. Here the authors devise a symmetry-based framework to create such non-equilibrium steady states showing characteristics of degenerate vacua of a unitary topological system.

    • Raul A. Santos
    • , Fernando Iemini
    •  & Yuval Gefen

  • Article
    | Open Access

    Time-dependent errors are one of the main obstacles to fully-fledged quantum information processing. Here, the authors develop a general methodology to monitor time-dependent errors, which could be used to make other characterisation protocols time-resolved, and demonstrate it on a trapped-ion qubit.

    • Timothy Proctor
    • , Melissa Revelle
    •  & Kevin Young

  • Article
    | Open Access

    Deterministic generation of photonic multi-partite entangled states has previously been achieved for specific states using ad-hoc devices. Here, the authors present a single superconducting circuit device to deterministically generate a variety of states, namely W, GHZ, and cluster states.

    • Jean-Claude Besse
    • , Kevin Reuer
    •  & Christopher Eichler

  • Article
    | Open Access

    The trade-off between long lifetime and inevitable radiative decay to a control line has become a key limitation for superconducting qubits. Here, the authors break the trade-off by coupling another qubit to the control line of the first one to suppress its relaxation, while enabling fast qubit control.

    • S. Kono
    • , K. Koshino
    •  & Y. Nakamura

  • Article
    | Open Access

    While most results so far in semiconductor spin-based quantum computation use electron spins, devices based on hole spins may have more favourable properties for quantum applications. Here, the authors demonstrate single-shot readout and coherent control of a qubit made from a single hole spin.

    • N. W. Hendrickx
    • , W. I. L. Lawrie
    •  & M. Veldhorst

  • Article
    | Open Access

    Here, the authors devise an exact protocol that simultaneously entangles arbitrary pairs of qubits on a trapped-ion quantum computer. The protocol requires classical computational resources polynomial in the system size, and very little overhead in the quantum control compared to a single-pair case.

    • Nikodem Grzesiak
    • , Reinhold Blümel
    •  & Yunseong Nam

  • Article
    | Open Access

    Individually addressed rare earth atoms in solid crystals are an emerging platform for quantum information processing. Here the authors demonstrate a key requirement, by realizing single-shot, quantum non-demolition measurements of the spin of single Er3+ ions in Y2SiO5 crystals with nearly 95% fidelity.

    • Mouktik Raha
    • , Songtao Chen
    •  & Jeff D. Thompson

  • Article
    | Open Access

    Conventional qubit readout methods in silicon spin qubits destroy the quantum state, precluding any further computations based on the outcome. Here, the authors demonstrate quantum non-demolition readout using a second qubit of the same kind, making for a scalable approach.

    • J. Yoneda
    • , K. Takeda
    •  & S. Tarucha

  • Article
    | Open Access

    Quantum process tomography represents one of the workhorses of quantum information processing, but suffers from exponential resource scaling. Here, the authors propose to efficiently infer general processes by approximating them through a sequence of two-qubit processes, and demonstrate it on a three-qubit case.

    • L. C. G. Govia
    • , G. J. Ribeill
    •  & H. Krovi

  • Article
    | Open Access

    Quantum dots are often referred to as “artificial atoms” as they create zero-dimensional traps for electrons, with characteristic atom-like spectra. Leon et al. demonstrate that higher shell and orbital states of a multi-electron silicon quantum dot with better control fidelity than single electron dots.

    • R. C. C. Leon
    • , C. H. Yang
    •  & A. S. Dzurak

  • Article
    | Open Access

    Qubits in solid state systems like point defects in diamond can be influenced by local strain. Here the authors use surface acoustic waves to coherently control silicon vacancies in diamond, which have the potential to reach the strong coupling regime necessary for many applications.

    • Smarak Maity
    • , Linbo Shao
    •  & Marko Lončar

  • Article
    | Open Access

    Semiconductor quantum dots are controlled by external fields that are tuned in order to optimise for information storage or inter-qubit interaction. Here the authors identify a working point for long-range interactions that can be reached with continuous protection from environmental noise.

    • J. C. Abadillo-Uriel
    • , M. A. Eriksson
    •  & Mark Friesen

  • Article
    | Open Access

    Certain point defects in crystals can be used as optically addressable quantum bits, much like atoms trapped in vacuum. Ivády et al. show that embedding such artificial atoms in stacking faults can actually improve their optical properties, making them function even more like true atoms.

    • Viktor Ivády
    • , Joel Davidsson
    •  & Adam Gali

  • Article
    | Open Access

    One of the main sources of decoherence in silicon electron spin qubits is their interaction with nearby fluctuating nuclear spins. Zhao et al. present a device made from enriched silicon to reduce the nuclear spin density and find its performance is still limited by fluctuations of residual spins.

    • R. Zhao
    • , T. Tanttu
    •  & A. S. Dzurak

  • Article
    | Open Access

    Checking the quality of operations of quantum computers in a reliable and scalable way is still an open challenge. Here, the authors show how to characterise multi-qubit operations in a way that scales favourably with the system’s size, and demonstrate it on a 10-qubit ion-trap device.

    • Alexander Erhard
    • , Joel J. Wallman
    •  & Rainer Blatt

  • Article
    | Open Access

    Different qubit platforms each have their own advantages and disadvantages. By engineering couplings between them it may be possible to create a more capable hybrid device. Here the authors demonstrate coherent coupling between a semiconductor spin qubit and a superconducting transmon.

    • A. J. Landig
    • , J. V. Koski
    •  & K. Ensslin

  • Article
    | Open Access

    Surface acoustic waves are promising candidates to convey flying qubits through semiconductor circuits. The authors investigate the central building block of such a circuit in an experiment and present a route to realise quantum logic gates with flying electrons that are surfing on a sound-wave.

    • Shintaro Takada
    • , Hermann Edlbauer
    •  & Christopher Bäuerle

  • Article
    | Open Access

    Accurately characterizing the noise influencing quantum devices is instrumental to improve coherence properties and design more robust control protocols. Sung et al. demonstrate non-Gaussian noise spectroscopy with a superconducting qubit, enabling the detection and characterization of dephasing noise without assuming Gaussian statistics.

    • Youngkyu Sung
    • , Félix Beaudoin
    •  & William D. Oliver

  • Article
    | Open Access

    The coherence times of nitrogen-vacancy centres are key factors influencing their performance in quantum applications. Here the authors show that synthesising phosphorus-doped diamond yields nitrogen-vacancy centres with significantly improved \(T_2^ \ast\) and T2.

    • E. D. Herbschleb
    • , H. Kato
    •  & N. Mizuochi

  • Article
    | Open Access

    Measurement-based quantum computing is one of the most promising approaches for photon-based universal quantum computation. Here, the authors realise a universal encoder of four-photon graph states on a silicon chip, and use Bayesian inference methods to characterise the error sources.

    • Jeremy C. Adcock
    • , Caterina Vigliar
    •  & Mark G. Thompson

  • Article
    | Open Access

    Molecular spin qubits show great promise for quantum information processing, but loss of phase information due to noise interference hinders their applicability. Here the authors engineer the electronic configurations of the metal centres in a series of divalent rare-earth complexes and succeed in prolonging their phase memory times.

    • Ana-Maria Ariciu
    • , David H. Woen
    •  & Floriana Tuna

  • Article
    | Open Access

    Magnetic-based isolators are critical components for protecting qubits against noise in quantum setups but unsuitable for large processors. Here, Abdo et al. show good protection of a qubit in a high-fidelity quantum readout setup using a Josephson-based isolator devoid of magnetic materials.

    • Baleegh Abdo
    • , Nicholas T. Bronn
    •  & Jerry M. Chow

  • Article
    | Open Access

    Gate-reflectometry is a recently demonstrated measurement technique for single spin states in silicon. It is potentially able to perform quantum non-demolition measurements and uses compact circuitry that can be scaled up to larger quantum computers. Crippa et al. successfully combine gate-reflectometry qubit readout and coherent control.

    • A. Crippa
    • , R. Ezzouch
    •  & S. De Franceschi

  • Article
    | Open Access

    There is an extensive literature discussing the potential applications of individual nitrogen vacancy centres but some proposed developments require the use of multiple, coupled defects. Here the authors demonstrate a method to fabricate coupled nitrogen vacancy centre triplets.

    • Moriyoshi Haruyama
    • , Shinobu Onoda
    •  & Osamu Hanaizumi

  • Article
    | Open Access

    High-dimensional quantum bits advance the application of quantum sensing and information processing technologies but suffer from the low spectral selectivity and working temperature. Here the authors present the selective excitation and control of spin qudits modes based on an ensemble of silicon vacancy defects in silicon carbide at room temperature.

    • V. A. Soltamov
    • , C. Kasper
    •  & V. Dyakonov

  • Article
    | Open Access

    Controllable two-qubit interactions are necessary to build a functional quantum computer. Here the authors demonstrate fast, coherent swapping of two spin states mediated by a long, multi-electron quantum dot that could act as a tunable coupler mediating interactions between multiple qubits.

    • Filip K. Malinowski
    • , Frederico Martins
    •  & Ferdinand Kuemmeth

  • Article
    | Open Access

    Universal cluster states for quantum computing can be assembled without feed-forward by fusing n-photon clusters with linear optics if the fusion success probability is above a threshold p. The authors bound p in terms of n and provide protocols for n = 3 clusters requiring lower fusion probability than before.

    • Mihir Pant
    • , Don Towsley
    •  & Saikat Guha

  • Article
    | Open Access

    As quantum computers grow in complexity the challenge of moving information between physically separated qubits becomes more pressing. Mills et al. demonstrate transfer of single electrons across an array of nine silicon quantum dots three orders of magnitude faster than spin qubit decoherence times.

    • A. R. Mills
    • , D. M. Zajac
    •  & J. R. Petta

  • Article
    | Open Access

    Quantum sensors can have exceptional properties but the limits on their performance involve nonclassical effects such as quantum backaction. Here the authors show how to mitigate the effects of backaction on the spectral resolution of an NV centre nuclear spin sensor by controlling the measurement strength.

    • Matthias Pfender
    • , Ping Wang
    •  & Jörg Wrachtrup

  • Article
    | Open Access

    The observation of magnetic field dependence of defects hosted in hBN has been elusive so far. Here, the authors perform an investigation of spin-related effects in the optical emission from hBN defects, and observe a magnetic field dependence in the intensity of the photoluminescence spectrum.

    • Annemarie L. Exarhos
    • , David A. Hopper
    •  & Lee C. Bassett

  • Article
    | Open Access

    Information Theoretically-secure deterministic programs that self-destruct after a single use are known to be impossible to implement. Here, the authors use quantum states to implement a probabilistic version of this fundamental cryptographic primitive, and provide a proof-of-principle implementation with single photons.

    • Marie-Christine Roehsner
    • , Joshua A. Kettlewell
    •  & Philip Walther

  • Article
    | Open Access

    The race to produce a quantum computer has driven the development of many different qubit designs with different benefits and drawbacks. Noiri et al. demonstrate a hybrid device with two coupled semiconductor spin qubits of different designs, which should allow each qubit’s advantages to be exploited.

    • A. Noiri
    • , T. Nakajima
    •  & S. Tarucha

  • Article
    | Open Access

    A transmon qubit insensitive to magnetic fields is a crucial element in topological quantum computing. Here, Kroll et al. create graphene transmons by integrating monolayer graphene Josephson junctions into microwave frequency superconducting circuits, allowing them to operate in a parallel magnetic field of 1 T.

    • J. G. Kroll
    • , W. Uilhoorn
    •  & L. P. Kouwenhoven

  • Article
    | Open Access

    Significant progress has been made developing the different methods needed for a spin-based quantum computer but the challenge of integrating them remains. Fogarty et al. present a system with single-spin addressability, spin-spin interactions and high-fidelity readout that provides a scalable foundation for error-corrected devices.

    • M. A. Fogarty
    • , K. W. Chan
    •  & A. S. Dzurak

  • Article
    | Open Access

    Bounding the capacity of thermal attenuators would give a powerful instrument to describe decoherence occurring in optical fibres and free space links. Here, the authors improve on the existing upper bounds in the region of small thermal noise, which is of interest for quantum communication.

    • Matteo Rosati
    • , Andrea Mari
    •  & Vittorio Giovannetti

  • Article
    | Open Access

    Quantum nonlocality is known to be reducible to quantum uncertainty and steering, but it is unclear whether steering is actually as essential as uncertainty. Here, the authors show that both steering and uncertainty play a role in determining optimal strategies in nonlocal games.

    • Ravishankar Ramanathan
    • , Dardo Goyeneche
    •  & Paweł Horodecki

  • Article
    | Open Access

    Germanium’s electronic structure and large, tunable spin-orbit coupling makes it a good material for constructing hole-based quantum devices. Here the authors demonstrate the fabrication and two-axis control of a hole spin qubit in a germanium double quantum dot.

    • Hannes Watzinger
    • , Josip Kukučka
    •  & Georgios Katsaros

  • Article
    | Open Access

    Metamaterials remain relatively unexplored in quantum optics. Here, the authors couple a transmon qubit to a superconducting metamaterial with a deep sub-wavelength lattice constant and probe the coherent and dissipative dynamics of the system by measuring the Lamb shift and radiative lifetime of the qubit.

    • Mohammad Mirhosseini
    • , Eunjong Kim
    •  & Oskar Painter

  • Article
    | Open Access

    Interfacing quantum information between discrete and continuous would allow exploiting the best of both worlds, but it has been shown only for single-rail encoding. Here, the authors extend this to the more practical dual-rail encoding, realizing teleportation between a polarization qubit and a CV qubit.

    • Demid V. Sychev
    • , Alexander E. Ulanov
    •  & A. I. Lvovsky

  • Article
    | Open Access

    Holonomic quantum gates represent a promising route to noise-tolerant quantum operations. Here, the authors use polarised microwaves to implement nonadiabatic holonomic quantum gates at room temperature and zero magnetic field on NV centers, both on single-qubit and between electron and nuclear spins.

    • Kodai Nagata
    • , Kouyou Kuramitani
    •  & Hideo Kosaka

  • Article
    | Open Access

    Methods for coherently transferring quantum states are needed in order to develop larger scale quantum devices. Here the authors implement an adiabatic transfer protocol in a triple quantum dot and show that dephasing noise can accelerate the process while maintaining the coherence of the transferred state.

    • Takashi Nakajima
    • , Matthieu R. Delbecq
    •  & Seigo Tarucha

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