Quantum physics

  • Article
    | Open Access

    Strong light-matter coupling has been realized at the level of single atoms and photons throughout most of the electromagnetic spectrum, except for the THz range. Here, the authors report a THz-scale transport gap, induced by vacuum fluctuations in carbon nanotube quantum dot through the deep strong coupling of a single electron to a THz resonator.

    • F. Valmorra
    • , K. Yoshida
    •  & T. Kontos
  • Article
    | Open Access

    N00N states are a key resource in quantum metrology, but the use of their multi-mode extension for multiparameter estimation has been elusive so far. Here, the authors use multi-mode N00N states - with N=2 photons in 4 modes - for multiple-phase estimation saturating the quantum Cramer-Rao bound.

    • Seongjin Hong
    • , Junaid ur Rehman
    •  & Hyang-Tag Lim
  • Article
    | Open Access

    So far, experimental results have favoured the often unstated assumption that quantum statistical properties of multiparticle systems are preserved in plasmonic platforms. Here, the authors show how multiparticle interference in photon-plasmon scattering can modify the excitation mode of plasmonic systems.

    • Chenglong You
    • , Mingyuan Hong
    •  & Omar S. Magaña-Loaiza
  • Article
    | Open Access

    Quantifying dimensionality of high-dimensional entangled states is challenging, especially in the presence of mixedness and noise. Here, the authors propose and demonstrate a method to quantify the dimensionality and purity of a bi-photon HD entangled state, scaling linearly with entanglement dimension.

    • Isaac Nape
    • , Valeria Rodríguez-Fajardo
    •  & Andrew Forbes
  • Article
    | Open Access

    Efficient conversion of microwave photons into electrical current would enable several applications in quantum technologies, especially if one could step outside of the gated-time regime. Here, the authors demonstrate continuous-time microwave photoconversion in double quantum dots with 6% efficiency.

    • Waqar Khan
    • , Patrick P. Potts
    •  & Ville F. Maisi
  • Article
    | Open Access

    The question whether a given isolated quantum many-body system would thermalize has currently no general answer. Here, Shiraishi and Matsumoto demonstrate the computational universality of thermalization phenomena already for simplified 1D systems, thus proving that the thermalization problem is undecidable.

    • Naoto Shiraishi
    •  & Keiji Matsumoto
  • Article
    | Open Access

    The way quantum simulation algorithms are translated into specific hardware implementations often translates into additional overhead. Here, the authors improve the efficiency of Hamiltonian simulation using a method that allows efficient synthesis of multi-qubit evolutions from two-qubit interactions.

    • Laura Clinton
    • , Johannes Bausch
    •  & Toby Cubitt
  • Article
    | Open Access

    In quantum mechanics, counterfactual behaviours are generally associated with particles being affected by events taking place where they can’t be found. Here, the authors consider extended quantum Cheshire cat scenarios where a particle can be influenced in regions where only its disembodied property has entered.

    • Yakir Aharonov
    • , Eliahu Cohen
    •  & Sandu Popescu
  • Article
    | Open Access

    Microcavity exciton-polaritons in atomically thin semiconductors are a promising platform for valley manipulation. Here, the authors show valley-selective control of polariton energies in monolayer WS2 using the optical Stark effect, thereby extending coherent valley manipulation to a hybrid light-matter regime

    • Trevor LaMountain
    • , Jovan Nelson
    •  & Nathaniel P. Stern
  • Article
    | Open Access

    It was predicted that complex thermalizing behaviour can arise in many-body systems in the absence of disorder. Here, the authors observe non-ergodic dynamics in a tilted optical lattice that is distinct from previously studied regimes, and propose a microscopic mechanism that is due to emergent kinetic constrains.

    • Sebastian Scherg
    • , Thomas Kohlert
    •  & Monika Aidelsburger
  • Article
    | Open Access

    Current hypotheses towards quantisation of gravity imply the presence of a minimal length scale, which may have a role in explaining quantum-to-classical transition. Here, the authors show how assuming the minimal length scale to be a fluctuating quantity leads to a possible universal decoherence mechanism.

    • Luciano Petruzziello
    •  & Fabrizio Illuminati
  • Article
    | Open Access

    Spin defects in two-dimensional materials potentially offer unique advantages for quantum sensing in terms of sensitivity and functionality. Here, the authors demonstrate the use of spin defects in hexagonal boron nitride as sensors of magnetic field, temperature and pressure, and show that their performance is comparable or exceeds that of existing platforms.

    • Andreas Gottscholl
    • , Matthias Diez
    •  & Vladimir Dyakonov
  • Article
    | Open Access

    Single-molecular magnets (SMM) are promising candidates for quantum technologies given the ease of repeatable manufacture and potential as qudits. Here, Biard et al succeed in electronically reading out a SMM containing two high-spin terbium atoms, allowing for a 16 dimensional Hilbert space.

    • Hugo Biard
    • , Eufemio Moreno-Pineda
    •  & Franck Balestro
  • Article
    | Open Access

    Several key tasks in quantum information processing can be regarded as channel manipulation. Here, focusing on the class of distillation protocols, the authors derive general bounds on resource overhead and incurred errors, showing application to magic state distillation and quantum channel capacities.

    • Bartosz Regula
    •  & Ryuji Takagi
  • Article
    | Open Access

    Nuclear spins in diamond are promising for applications in quantum technologies due to their long coherence times. Here, the authors demonstrate a scalable electrical readout of individual intrinsic 14N nuclear spins in diamond, mediated by hyperfine coupling to electron spin of the NV center, as a step towards room-temperature nanoscale diamond quantum devices.

    • Michal Gulka
    • , Daniel Wirtitsch
    •  & Milos Nesladek
  • Article
    | Open Access

    Photon echo techniques are difficult to implement in the quantum regime due to coherent and spontaneous emission noise. Here, the authors propose a low-noise photon-echo quantum memory approach based on all-optical control in a four-level system, and demonstrate it using a Eu3+:Y2SiO5 crystal.

    • You-Zhi Ma
    • , Ming Jin
    •  & Guang-Can Guo
  • Article
    | Open Access

    Single atom magnets on surfaces offer potentially long lived and stable spin states, particular lanthanides, which can be adsorbed onto Magnesium Oxide. Here, the authors report on Dysprosium adsorbed onto Magnesium Oxide, which exhibits large magnetic anisotropy energy, and a spin life time of several days at low temperatures

    • A. Singha
    • , P. Willke
    •  & T. Choi
  • Article
    | Open Access

    Hybrid devices based on electrons on helium may find application in quantum devices. Here the authors demonstrate surface acoustic wave driven acoustoelectric transport of electrons on superfluid helium.

    • H. Byeon
    • , K. Nasyedkin
    •  & J. Pollanen
  • Article
    | Open Access

    Long-range coherent spin-qubit transfer between semiconductor quantum dots requires understanding and control over associated errors. Here, the authors achieve high-fidelity coherent state transfer in a Si double quantum dot, underpinning the prospects of a large-scale quantum computer.

    • J. Yoneda
    • , W. Huang
    •  & A. S. Dzurak
  • Article
    | Open Access

    Physical principles underlying machine learning analysis of quantum gas microscopy data are not well understood. Here the authors develop a neural network based approach to classify image data in terms of multi-site correlation functions and reveal the role of fourth-order correlations in the Fermi-Hubbard model.

    • Cole Miles
    • , Annabelle Bohrdt
    •  & Eun-Ah Kim
  • Article
    | Open Access

    Accurate control of the spatial location and the emission wavelength of single photon emitters (SPEs) in van der Waals materials is a crucial yet challenging endeavour. Here, the authors use an electron beam to generate SPE ensembles in high purity synthetic hBN with enhanced spatial accuracy and emission reproducibility.

    • Clarisse Fournier
    • , Alexandre Plaud
    •  & Aymeric Delteil
  • Article
    | Open Access

    Tensor network simulations of lattice gauge theories may overcome the limitations of the Monte Carlo approach, but results have been limited to 1+1 and 2+1 dimensions so far. Here, the authors report a tree-tensor-based numerical study of a 3+1d truncated U(1) lattice gauge theory with fermionic matter.

    • Giuseppe Magnifico
    • , Timo Felser
    •  & Simone Montangero
  • Article
    | Open Access

    Control of quantum emitters is needed in order to enable many applications. Here, the authors demonstrate enhancement and dynamical control of the Purcell emission from erbium ions doped in a nanoparticle within a fiber-based microcavity.

    • Bernardo Casabone
    • , Chetan Deshmukh
    •  & Hugues de Riedmatten
  • Article
    | Open Access

    The use of optically addressable spins to control dark electron-spins is promising for multi-qubit platforms; however, control over darks spins has remained challenging. Here, the authors realize entanglement between individual dark spins associated with substitutional nitrogen defects in diamond.

    • M. J. Degen
    • , S. J. H. Loenen
    •  & T. H. Taminiau
  • Article
    | Open Access

    Multi-donor molecules in Si provide a promising qubit platform, offering advantages over single donor qubits in terms of performance and fabrication. Here, the authors report a single qubit gate and long coherence times in a P donor molecule qubit in natural Si patterned by scanning tunneling microscope hydrogen lithography.

    • Lukas Fricke
    • , Samuel J. Hile
    •  & Michelle Y. Simmons
  • Article
    | Open Access

    Optically detected magnetic resonance of defect spins typically relies on Stokes excitation, in which the excitation energy is larger than that of the emitted photon. Here, the authors use the opposite regime of anti-Stokes excitation to detect Si vacancy spins in SiC, with a threefold improvement in signal contrast.

    • Jun-Feng Wang
    • , Fei-Fei Yan
    •  & Guang-Can Guo
  • Article
    | Open Access

    Multielectron quantum dots offer a promising platform for high-performance spin qubits; however, previous demonstrations have been limited to single-qubit operation. Here, the authors report a universal gate set and two-qubit Bell state tomography in a high-occupancy double quantum dot in silicon.

    • Ross C. C. Leon
    • , Chih Hwan Yang
    •  & Andrew S. Dzurak
  • Article
    | Open Access

    Non-Abelian statistics plays a crucial role towards realizing topological quantum computation. Here, the authors discover new types of non-Abelian three-loop braiding statistics that can only be realized in 3D interacting fermionic systems.

    • Jing-Ren Zhou
    • , Qing-Rui Wang
    •  & Zheng-Cheng Gu
  • Article
    | Open Access

    Rectenna, which consist of a microscale antenna, combined with a rectifying diode, have great potential in energy harvesting, however, achieving high responsivity and low resistance is extremely difficult. Here, the authors demonstrate a metal-insulator-insulator metal diode which overcomes these limitations.

    • Amina Belkadi
    • , Ayendra Weerakkody
    •  & Garret Moddel
  • Article
    | Open Access

    Device-independent quantum key distribution aims at the ultimate quantum-based unconditional security, but current protocols’ rates are quite far from anything practical. The authors’ protocol narrows this gap by using two randomly chosen key generating bases instead of one.

    • René Schwonnek
    • , Koon Tong Goh
    •  & Charles C.-W. Lim
  • Article
    | Open Access

    Background radiation has been identified as a key factor limiting the coherence times of superconducting circuits. Here, the authors measure the impact of environmental and cosmic radiation on a superconducting resonator with varying degrees of shielding, including an underground facility.

    • L. Cardani
    • , F. Valenti
    •  & I. M. Pop
  • Article
    | Open Access

    High-resolution microwave detection with NV centers in diamond is currently applicable to signals with frequencies below 10 MHz, thus limiting their range of applications. Here, the authors demonstrate detection of GHz signals with sub-Hz spectral resolution, not limited by the quantum sensor lifetime.

    • Jonas Meinel
    • , Vadim Vorobyov
    •  & Jörg Wrachtrup
  • Article
    | Open Access

    Expectations for quantum machine learning are high, but there is currently a lack of rigorous results on which scenarios would actually exhibit a quantum advantage. Here, the authors show how to tell, for a given dataset, whether a quantum model would give any prediction advantage over a classical one.

    • Hsin-Yuan Huang
    • , Michael Broughton
    •  & Jarrod R. McClean
  • Article
    | Open Access

    Gamma photons used in positron emission tomography are predicted to be produced in an entangled state. Here, the authors simulate the effects of entanglement and test them through comparison with experimental data from a PET demonstrator apparatus, showing the potential gains in background suppression.

    • D. P. Watts
    • , J. Bordes
    •  & N. A. Zachariou
  • Article
    | Open Access

    Atom interferometers can be useful for precision measurement of fundamental constants and sensors of different type. Here the authors demonstrate a compact twin-lattice atom interferometry exploiting Bose-Einstein condensates (BECs) of 87 Rb atoms.

    • Martina Gebbe
    • , Jan-Niclas Siemß
    •  & Ernst M. Rasel
  • Article
    | Open Access

    Previous work has demonstrated electric-field detection with nitrogen-vacancy centers in diamond; however, nanoscale electric-field imaging has not been shown. Here, the authors use individual nitrogen-vacancy centers to map out electric field contours from a tip of an atomic force microscope with 10 nm resolution.

    • Ke Bian
    • , Wentian Zheng
    •  & Ying Jiang
  • Article
    | Open Access

    Steering reflects the ability to predict measurement results on one side of a quantum-correlated system based on measurements on the other side, which can be phrased as a metrology problem. Here, the authors explore this connection, deriving a general steering criterion based on quantum Fisher information.

    • Benjamin Yadin
    • , Matteo Fadel
    •  & Manuel Gessner
  • Article
    | Open Access

    Quantum memories are key components for quantum communication, but current storage times are still too short. Here, the authors use the atomic frequency comb protocol in a zero-first-order-Zeeman field to coherently store an optical pulse for an hour in a cryogenically cooled rare-earth doped crystal.

    • Yu Ma
    • , You-Zhi Ma
    •  & Guang-Can Guo
  • Article
    | Open Access

    Discrete time crystals are typically characterized by a period doubled response with respect to an external drive. Here, the authors predict the emergence of rich dynamical phases with higher-order and fractional periods in clean spin-1/2 chains with long-range interactions.

    • Andrea Pizzi
    • , Johannes Knolle
    •  & Andreas Nunnenkamp
  • Article
    | Open Access

    Integrated sources of nonclassical light are a key component for scalable quantum technologies. Here, the authors work with two coupled microring resonators and show how to detune the resonances involved in unwanted parametric fluorescence, without significantly affecting the pump power efficiency.

    • Y. Zhang
    • , M. Menotti
    •  & Z. Vernon
  • Article
    | Open Access

    The surface code is a keystone in quantum error correction, but it does not generally perform well against structured noise and suffers from large overheads. Here, the authors demonstrate that a variant of it has better performance and requires fewer resources, without additional hardware demands.

    • J. Pablo Bonilla Ataides
    • , David K. Tuckett
    •  & Benjamin J. Brown
  • Article
    | Open Access

    Previous demonstrations of spin state transfer in quantum dot chains relied on physical motion of electrons or sequences of SWAP operations. Here, the authors implement an alternative method based on adiabatic evolution, offering advantages in terms of implementation and robustness to noise and errors.

    • Yadav P. Kandel
    • , Haifeng Qiao
    •  & John M. Nichol
  • Article
    | Open Access

    Establishing whether two quantum channels are compatible is a fundamental problem in quantum information. Here, the authors prove its equivalence to the quantum state marginal problem, introduce an efficient way to solve both, and draw further connection to the measurement compatibility problem.

    • Mark Girard
    • , Martin Plávala
    •  & Jamie Sikora
  • Article
    | Open Access

    Information transfer between distant qubits suffers from spurious interactions and disorder. Here, the authors report up to an order of magnitude enhancement in the quality factor of a swap operation of eigenstates in a quantum dot chain, by using a periodic driving protocol inspired by discrete time crystals.

    • Haifeng Qiao
    • , Yadav P. Kandel
    •  & John M. Nichol