Quantum information articles within Nature Communications

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  • 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

    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

    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

  • Article
    | Open Access

    Topological quantum error correction is a promising approach towards fault-tolerant quantum computing, but suffers from large time overhead. Here, the authors generalise the stabiliser toric code to a single-shot 3D subsystem toric code, featuring good performance and resilience to measurement errors.

    • Aleksander Kubica
    •  & Michael Vasmer

  • Article
    | Open Access

    The use of machine learning to characterise quantum states has been demonstrated, but usually training the algorithm using data from the same state one wants to characterise. Here, the authors show an algorithm that can learn all states that share structural similarities with the ones used for the training.

    • Yan Zhu
    • , Ya-Dong Wu
    •  & Giulio Chiribella

  • Article
    | Open Access

    Investigations of quantum thermal machines and Liouvillian exceptional points have rarely crossed each other. Here, the authors realize experimentally a quantum Otto engine using a single trapped ion, and show that crossing a Liouvillian exceptional point during the cycle increases the engine performance.

    • J.-W. Zhang
    • , J.-Q. Zhang
    •  & M. Feng

  • Article
    | Open Access

    Fibre-based entanglement distribution represents a key primitive for quantum applications such as QKD. Here, the authors demonstrate it across 248 km of deployed fiber, observing stable detected pair rates of 9 Hz for 110 h.

    • Sebastian Philipp Neumann
    • , Alexander Buchner
    •  & Rupert Ursin

  • Article
    | Open Access

    The Fermi-Hubbard model represents one of the benchmarks for testing quantum computational methods for condensed matter. Here, the authors are able to reproduce qualitative properties of the model on 1 × 8 and 2 × 4 lattices, by running a VQE-based algorithm on a superconducting quantum processor.

    • Stasja Stanisic
    • , Jan Lukas Bosse
    •  & Ashley Montanaro

  • Comment
    | Open Access

    What is an optimal parameter landscape and geometric layout for a quantum processor so that its qubits are sufficiently protected for idling and simultaneously responsive enough for fast entangling gates? Quantum engineers pondering the dilemma might want to take a look on tools developed for many-body localization.

    • Matti Silveri
    •  & Tuure Orell

  • Article
    | Open Access

    A coherent quantum link between distant quantum processors is desirable for scaling up of quantum computation. Noiri et al. demonstrate a strategy to link distant quantum processors in silicon, by implementing a shuttling-based two-qubit gate between spin qubits in a Si/SiGe triple quantum dot.

    • Akito Noiri
    • , Kenta Takeda
    •  & Seigo Tarucha

  • Article
    | Open Access

    There are several proposals for quantum algorithms solving optimisation problems, but so far none of them has provided a clear speedup. Here, the authors propose an iterative protocol featuring periodic cycling around the tricritical point of a many-body localization transition.

    • Hanteng Wang
    • , Hsiu-Chung Yeh
    •  & Alex Kamenev

  • Article
    | Open Access

    Signals that look the same from their low-order correlations can often be distinguished by looking at higher-order ones. Here, the authors exploit the sensitivity of quantum nonlinear spectroscopy to fourth-order correlations to identify Gaussian noises, random-phased AC fields, and quantum spins.

    • Jonas Meinel
    • , Vadim Vorobyov
    •  & J. Wrachtrup

  • Article
    | Open Access

    The power of quantum machine learning algorithms based on parametrised quantum circuits are still not fully understood. Here, the authors report rigorous bounds on the generalisation error in variational QML, confirming how known implementable models generalize well from an efficient amount of training data.

    • Matthias C. Caro
    • , Hsin-Yuan Huang
    •  & Patrick J. Coles

  • Article
    | Open Access

    It has been predicted that longitudinal coupling between a qubit and a superconducting resonator can mediate efficient interactions among distant qubits. Here the authors implement such a coupling between a singlet-triplet qubit in a semiconductor double quantum dot and a high-impedance superconducting resonator.

    • C. G. L. Bøttcher
    • , S. P. Harvey
    •  & A. Yacoby

  • Article
    | Open Access

    Continuous-variable QKD protocols are usually easier to implement than discrete-variables ones, but their security analyses are less developed. Here, the authors propose and demonstrate in the lab a CVQKD protocol that can generate composable keys secure against collective attacks.

    • Nitin Jain
    • , Hou-Man Chin
    •  & Ulrik L. Andersen

  • Article
    | Open Access

    In strong field ionization, entanglement between an electron and an ion has been discussed previously. Here the authors explore orbital angular momentum entanglement between the electrons released in non-sequential double ionization.

    • Andrew S. Maxwell
    • , Lars Bojer Madsen
    •  & Maciej Lewenstein

  • Article
    | Open Access

    In quantum computing, realistic error models can allow tailored correction schemes for specific platforms. Here, while considering the case of qubits encoded in metastable electronic levels of atomic arrays, the authors propose a way to convert a large fraction of occurring errors into detectable leakages, or erasure errors, which are vastly easier to correct.

    • Yue Wu
    • , Shimon Kolkowitz
    •  & Jeff D. Thompson

  • Article
    | Open Access

    Full tomography of biphoton frequency comb states requires frequency mixing operations which are hard to scale. Here, the authors propose and demonstrate a protocol exploiting advanced Bayesian statistical methods and randomized measurements coming from complex mode mixing in electro-optic phase modulators.

    • Hsuan-Hao Lu
    • , Karthik V. Myilswamy
    •  & Joseph M. Lukens

  • Article
    | Open Access

    Quantum neural networks could help analysing the output of quantum computers and quantum simulators of growing complexity. Here, the authors use a 7-qubit superconducting quantum processor to show how a quantum convolutional neural network can correctly recognise the phase of a quantum many-body state.

    • Johannes Herrmann
    • , Sergi Masot Llima
    •  & Christopher Eichler

  • Article
    | Open Access

    Hybrid quantum devices based on coupled nuclear and electron spins offer promising applications, but require long nuclear spin coherence times. Here the authors demonstrate millisecond coherence times for a nuclear spin ensemble coupled to a single electron spin qubit in a semiconductor quantum dot.

    • George Gillard
    • , Edmund Clarke
    •  & Evgeny A. Chekhovich

  • Article
    | Open Access

    The approach to stabilizing a quantum state by coupling to engineered reservoirs is limited by a trade-off between state fidelity and stabilization rate. Here the authors implement a protocol based on parametric system-bath coupling to achieve fast and high-fidelity Bell state stabilization in a qutrit-qubit system.

    • T. Brown
    • , E. Doucet
    •  & L. Ranzani

  • Article
    | Open Access

    Measurement-device-independent QKD schemes suffer from a trade-off between ease of implementation (avoiding the need for global phase locking) and high rates (quadratic improvement in rate). Here, the authors propose a protocol which offers both simple implementation and strong performances.

    • Pei Zeng
    • , Hongyi Zhou
    •  & Xiongfeng Ma

  • Article
    | Open Access

    Graphene has long been considered to be a promising host for spin qubits, however a demonstration of long spin relaxation times for a potential qubit has been lacking. Here, the authors report the electrical measurement of the single-electron spin relaxation time exceeding 200 μs in a bilayer graphene quantum dot.

    • L. Banszerus
    • , K. Hecker
    •  & C. Stampfer

  • Article
    | Open Access

    Exotic quantum states can be advantageous for sensing, but are very fragile, so that some form of quantum error correction is needed. Here, the authors show how approximate QEC helps overcoming decoherence due to noise when measuring the excitation population of a receiver mode in a superconducting circuit.

    • W. Wang
    • , Z.-J. Chen
    •  & L. Sun

  • Article
    | Open Access

    Superconducting quantum processors need to balance intentional disorder (to protect qubits) and nonlinear resonator coupling (to manipulate qubits), while avoiding chaotic instabilities. Berke et al. use the techniques of many-body localization theory to study the stability of current platforms against quantum chaos.

    • Christoph Berke
    • , Evangelos Varvelis
    •  & David P. DiVincenzo

  • Article
    | Open Access

    Quantum memories usually suffer from a trade-off between efficiency and excess noise. Here, by exploiting the time-reversal approach for improving modes matching, the authors show a warm-atomic-cell-based cavity-enhanced memory with 67% efficiency and noise level close to quantum noise limit.

    • Lixia Ma
    • , Xing Lei
    •  & Kunchi Peng

  • Article
    | Open Access

    Continuous quantum error correction requires less ancillary resources compared to standard QEC methods. Here, the authors demonstrate experimentally a continuous quantum error correction code in a planar superconducting architecture.

    • William P. Livingston
    • , Machiel S. Blok
    •  & Irfan Siddiqi

  • Article
    | Open Access

    The presence of various noises in the qubit environment is a major limitation on qubit coherence time. Here, the authors demonstrate the use a closed-loop feedback to stabilize frequency noise in a flux-tunable superconducting qubit and suggest this as a scalable approach applicable to other types of noise.

    • Antti Vepsäläinen
    • , Roni Winik
    •  & William D. Oliver

  • Article
    | Open Access

    Quantum channel correction could provide a remedy to unavoidable losses in long-distance quantum communication, but the break-even point has escaped demonstration so far. Here, the authors fill this gap using distillation by heralded amplification, followed by teleportation of entanglement.

    • Sergei Slussarenko
    • , Morgan M. Weston
    •  & Geoff J. Pryde

  • Article
    | Open Access

    The current efforts to look for Majorana bound states (MBS) still cannot probe the hallmark property, the non-Abelian statistics. Here, the authors propose to realize non-Abelian statistics through MBS fusion in mini-gate controlled planar Josephson junctions.

    • Tong Zhou
    • , Matthieu C. Dartiailh
    •  & Igor Žutić

  • Article
    | Open Access

    Faithful conversion of quantum states between electrical circuits and light requires adding less than one input noise photon during conversion. Here, the authors demonstrate this based on coherent electro-optic upconversion with a transduction efficiency of 15%.

    • Rishabh Sahu
    • , William Hease
    •  & Johannes M. Fink

  • Article
    | Open Access

    Qudit-based quantum devices can outperform qubit-based ones, but a programmable qudit-based quantum computing device is still missing. Here, the authors fill this gap using a programmable silicon photonic chip employing ququart-based encoding, showing the scaling advantages compared to the qubit counterpart.

    • Yulin Chi
    • , Jieshan Huang
    •  & Jianwei Wang

  • Article
    | Open Access

    Applying the language of computational complexity to study real-world experiments requires a rigorous framework. Here, the authors provide such a framework and establish that there can be an exponential savings in resources if an experimentalist can entangle apparatuses with experimental samples.

    • Dorit Aharonov
    • , Jordan Cotler
    •  & Xiao-Liang Qi

  • Article
    | Open Access

    Spin-orbit coupling in gate-defined quantum dots in silicon metal-oxide semiconductors provides a promising route for electrical control of spin qubits. Here, the authors demonstrate that intervalley spin–orbit interaction enables fast singlet–triplet qubit rotations in this platform, at frequencies exceeding 200MHz.

    • Ryan M. Jock
    • , N. Tobias Jacobson
    •  & Dwight R. Luhman

  • Article
    | Open Access

    Fluctuations, both quantum and classical, contain important information about the underlying system. Here, the authors show that for measurements on a subregion with a sharp corner, fluctuations have the same shape dependence for a large variety of systems.

    • Benoit Estienne
    • , Jean-Marie Stéphan
    •  & William Witczak-Krempa

  • Article
    | Open Access

    Hole-spin qubits in germanium are promising candidates for rapid, all-electrical qubit control. Here the authors report Rabi oscillations with the record frequency of 540 MHz in a hole-based double quantum dot in a germanium hut wire, which is attributed to strong spin-orbit interaction of heavy holes.

    • Ke Wang
    • , Gang Xu
    •  & Guo-Ping Guo

  • Article
    | Open Access

    Implementations of shortcuts to adiabaticity for open quantum systems have proven challenging so far. Here, thanks to a multi-mode open loop and a unitary control counteracting the diabatic part of the Liouvillian, the authors demonstrate how to close this gap using a superconducting circuit QED system.

    • Zelong Yin
    • , Chunzhen Li
    •  & Shuoming An

  • Article
    | Open Access

    Exploiting technologies derived from the optical clocks community, the authors demonstrate a setup for twin-field QKD which extends the coherence times by three orders of magnitude, overcoming the main challenge towards real-world implementation.

    • Cecilia Clivati
    • , Alice Meda
    •  & Davide Calonico

  • Article
    | Open Access

    Aumann’s agreement theorem states that observers of classical systems can’t “agree to disagree." Here, the authors show that the same epistemic consistency holds for observers of quantum states, but not for observers of post-quantum no-signalling boxes, hinting at its potential status as a physical principle.

    • Patricia Contreras-Tejada
    • , Giannicola Scarpa
    •  & Pierfrancesco La Mura

  • Article
    | Open Access

    Variational quantum algorithms (VQAs) are a leading candidate for useful applications of near-term quantum computing, but limitations due to unavoidable noise have not been clearly characterized. Here, the authors prove that local Pauli noise can cause vanishing gradients rendering VQAs untrainable.

    • Samson Wang
    • , Enrico Fontana
    •  & Patrick J. Coles

  • Article
    | Open Access

    The combination of superconducting nanowire single photon detectors and electro-optically reconfigurable circuits in a cryogenic environment is notoriously difficult to reach. Here, the authors realise this on a Lithium-Niobate-On-Insulator platform, reaching high speed modulation at a frequency up to 1 GHz.

    • Emma Lomonte
    • , Martin A. Wolff
    •  & Francesco Lenzini

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