Article
|
Open Access
Featured
-
-
Article
| Open AccessActive ballistic orbital transport in Ni/Pt heterostructure
The authors observe THz emission from Ni/Pt heterostructure due to long-range ballistic orbital transport. The velocity of orbital current can be optically tuned by laser fluence, opening the avenue for future optorbitronic devices.
- Sobhan Subhra Mishra
- , James Lourembam
- & Ranjan Singh
-
Article
| Open AccessBounds to electron spin qubit variability for scalable CMOS architectures
Understanding the microscopic variability of CMOS spin qubits is crucial for developing scalable quantum processors. Here the authors report a combined experimental and numerical study of the effect of interface roughness on variability of quantum dot spin qubits formed at the Si/SiO2 interface.
- Jesús D. Cifuentes
- , Tuomo Tanttu
- & Andre Saraiva
-
Article
| Open AccessEfficient multimode Wigner tomography
Standard ways of characterising quantum states incur exponential overhead. Here, the authors consider the task of reconstructing density matrices of multimode continuous variable systems, and demonstrate a method which scales polynomially with the system size, provided the state lies in a polynomial dimensional subspace.
- Kevin He
- , Ming Yuan
- & David I. Schuster
-
Article
| Open AccessEfficient characterizations of multiphoton states with an ultra-thin optical device
Shadow tomography is efficient for quantum state characterization. Here, the authors implement shadow tomography on photonic states with a single metasurface, which alleviates the complexity in measurement
- Kui An
- , Zilei Liu
- & He Lu
-
Article
| Open AccessMechanically induced correlated errors on superconducting qubits with relaxation times exceeding 0.4 ms
Significant efforts have been dedicated to understanding the mechanisms of decoherence in superconducting qubits. Here, using time-resolved error measurements, the authors link errors present in transmon qubits based on Nb electrodes to mechanical vibrations of a commonly used pulse tube cooler.
- Shingo Kono
- , Jiahe Pan
- & Tobias J. Kippenberg
-
Article
| Open AccessA linear response framework for quantum simulation of bosonic and fermionic correlation functions
As quantum simulations advance, the ability to measure response functions of simulated systems becomes increasingly important. Here the authors present a linear response framework for computing fermionic and bosonic response functions on a quantum computer, demonstrating advantages over existing methods.
- Efekan Kökcü
- , Heba A. Labib
- & A. F. Kemper
-
Article
| Open AccessMulti-site integrated optical addressing of trapped ions
A promising strategy for scaling trapped-ion-based quantum technologies is to use fully integrated optical waveguides to deliver light to numerous ions at multiple sites. Here, the authors. optically address three ions using on-chip waveguides to deliver three distinct wavelengths per ion, and perform Rabi flopping on each ion simultaneously.
- Joonhyuk Kwon
- , William J. Setzer
- & Hayden J. McGuinness
-
Article
| Open AccessTransition role of entangled data in quantum machine learning
Given that entangled states can store more information than unentangled ones, it would be natural to assume that highly-entangled data would always enhance capabilities of quantum machine learning models. Here, the authors show that this is not the case, in particular when the allowed number of measurements to incoherently learn quantum dynamics is low
- Xinbiao Wang
- , Yuxuan Du
- & Dacheng Tao
-
Article
| Open AccessSurpassing millisecond coherence in on chip superconducting quantum memories by optimizing materials and circuit design
Understanding loss mechanisms in superconducting circuits is crucial for improving qubit coherence. Here the authors use a multimode resonator to study loss mechanisms in thin-film superconducting circuits and demonstrate on-chip quantum memories with lifetimes exceeding 1ms, using Ta thin-films and high-temperature substrate annealing
- Suhas Ganjam
- , Yanhao Wang
- & Robert J. Schoelkopf
-
Article
| Open AccessA substitutional quantum defect in WS2 discovered by high-throughput computational screening and fabricated by site-selective STM manipulation
Point defects in 2D semiconductors have potential for quantum computing applications, but their controlled design and synthesis remains challenging. Here, the authors identify and fabricate a promising quantum defect in 2D WS2 via high-throughput computational screening and scanning tunnelling microscopy.
- John C. Thomas
- , Wei Chen
- & Geoffroy Hautier
-
Article
| Open AccessMeasuring statistics-induced entanglement entropy with a Hong–Ou–Mandel interferometer
Measuring quantum entanglement remains a demanding task. The authors introduce two functions to quantify entanglement induced by fermionic or bosonic statistics, in transport experiments. Both functions, in theory and experiment, are remarkably resilient against the nonuniversal effects of interactions.
- Gu Zhang
- , Changki Hong
- & Yuval Gefen
-
Article
| Open AccessHigh-throughput quantum photonic devices emitting indistinguishable photons in the telecom C-band
An efficient way of realising a large number of telecom single-photon emitters for quantum communication is still missing. Here, the authors use a wide-field imaging technique for fast localization of single InAs/InP quantum dots, which are then integrated into circular Bragg grating cavities featuring high single-photon purity and indistinguishability.
- Paweł Holewa
- , Daniel A. Vajner
- & Elizaveta Semenova
-
Article
| Open AccessReversibility of quantum resources through probabilistic protocols
The problem of reversibility within general quantum resource theories is still an open one. Here, the authors prove that a reversible entanglement manipulation framework (and, consequently, the concept of entanglement entropy) can be formally established by adjusting the setting to allow for probabilistic operations
- Bartosz Regula
- & Ludovico Lami
-
Article
| Open AccessNonlocality activation in a photonic quantum network
Entangled local states can be made capable of violating Bell inequalities via nonlocality activation. Typical theoretical approaches require processing many copies of the original state and performing joint measurements on the ensemble. Here, instead, the authors experimentally demonstrate how to do so using a single copy of the state, broadcasting it to two spatially separated parties within a three-node network.
- Luis Villegas-Aguilar
- , Emanuele Polino
- & Geoff J. Pryde
-
Matters Arising
| Open AccessQuantum mechanical rules for observed observers and the consistency of quantum theory
- Alexios P. Polychronakos
-
Article
| Open AccessFast joint parity measurement via collective interactions induced by stimulated emission
Parity detection is essential in quantum error correction. Here, authors propose a reliable joint parity measurement (JPM) scheme inspired by stimulated emission and experimentally implement the weight-2(4) JPM scheme in a tunable coupling superconducting circuit, which shows comparable performance to the standard CNOT-gate based scheme.
- Sainan Huai
- , Kunliang Bu
- & Yicong Zheng
-
Article
| Open AccessEnhancing combinatorial optimization with classical and quantum generative models
Solving combinatorial optimization problems using quantum or quantum-inspired machine learning models would benefit from strategies able to work with arbitrary objective functions. Here, the authors use the power of generative models to realise such a black-box solver, and show promising performances on some portfolio optimization examples.
- Javier Alcazar
- , Mohammad Ghazi Vakili
- & Alejandro Perdomo-Ortiz
-
Article
| Open AccessDemonstration of hypergraph-state quantum information processing
Usual multiqubit entangled states can be described using the graph formalism, where each edge connects only two qubits. Here, instead, the authors use a reprogrammable silicon photonics chip to showcase preparation, verification and processing of arbitrary four-qubit hypergraph states, where hyperedges describe entanglement within a subset of many qubits.
- Jieshan Huang
- , Xudong Li
- & Jianwei Wang
-
Article
| Open AccessEffective light cone and digital quantum simulation of interacting bosons
Studying bounds on the speed of information propagation across interacting boson systems is notoriously difficult. Here, the authors find tight bounds for both the transport of boson particles and information propagation, for arbitrary time-dependent Bose-Hubbard-type Hamiltonians in arbitrary dimensions.
- Tomotaka Kuwahara
- , Tan Van Vu
- & Keiji Saito
-
Article
| Open AccessUniversal control of a bosonic mode via drive-activated native cubic interactions
Manipulating quantum information encoded in a bosonic mode requires sizeable and controllable nonlinearities, but superconducting devices’ strong nonlinearities are normally static. Here, the authors use a SNAIL to suppress static nonlinearities and use drive-dependent ones to reach universal control of a bosonic mode.
- Axel M. Eriksson
- , Théo Sépulcre
- & Simone Gasparinetti
-
Article
| Open AccessOptimizing quantum gates towards the scale of logical qubits
Ensuring high-fidelity quantum gates while increasing the number of qubits poses a great challenge. Here the authors present a scalable strategy for optimizing frequency trajectories as a form of error mitigation on a 68-qubit superconducting quantum processor, demonstrating high single- and two-qubit gate fidelities.
- Paul V. Klimov
- , Andreas Bengtsson
- & Hartmut Neven
-
Article
| Open AccessSi/SiGe QuBus for single electron information-processing devices with memory and micron-scale connectivity function
Electron spin qubits in SiGe dots have emerged as promising candidates for quantum information processing. Here the authors demonstrate conveyor-mode single electron shuttling in a Si/SiGe quantum dot device spanning the length of 10 micrometres and operated with a small number of controls
- Ran Xue
- , Max Beer
- & Lars R. Schreiber
-
Article
| Open AccessUnderstanding quantum machine learning also requires rethinking generalization
Understanding machine learning models’ ability to extrapolate from training data to unseen data - known as generalisation - has recently undergone a paradigm shift, while a similar understanding for their quantum counterparts is still missing. Here, the authors show that uniform generalization bounds pessimistically estimate the performance of quantum machine learning models.
- Elies Gil-Fuster
- , Jens Eisert
- & Carlos Bravo-Prieto
-
Perspective
| Open AccessQuantum many-body simulations on digital quantum computers: State-of-the-art and future challenges
Digital quantum simulations of quantum many-body systems have emerged as one of the most promising applications of near-term quantum computing. This Perspective article provides an overview and an outlook on future developments in this field.
- Benedikt Fauseweh
-
Article
| Open AccessMapping a 50-spin-qubit network through correlated sensing
The ability to characterize large and complex nuclear-spin networks could enable quantum applications, such as quantum simulations of many-body physics. Here the authors develop a high-resolution quantum-sensing method and use it to image a network of 50 nuclear spins surrounding a single NV center in diamond.
- G. L. van de Stolpe
- , D. P. Kwiatkowski
- & T. H. Taminiau
-
Article
| Open AccessPractical high-dimensional quantum key distribution protocol over deployed multicore fiber
High-dimensional QKD would in principle allow for several advantages over its bidimensional counterpart, but in-the-field demonstrations are missing. Here, the authors realise 4- dimensional hybrid time-path-encoded QKD using a 52-km deployed multicore fiber link.
- Mujtaba Zahidy
- , Domenico Ribezzo
- & Davide Bacco
-
Article
| Open AccessAutonomous error correction of a single logical qubit using two transmons
Autonomous quantum error correction protects quantum systems against decoherence through engineered dissipation. Here the authors introduce the Star code, which actively corrects single-photon loss and passively suppresses low-frequency dephasing and implement it in a two-transmon device.
- Ziqian Li
- , Tanay Roy
- & David I. Schuster
-
Article
| Open AccessEnhancing detection of topological order by local error correction
Detection of topological phases in experiments is challenging, especially in the presence of incoherent noise. Cong et al. introduce a novel method combining error correction and renormalization-group flow and apply it to characterization of quantum spin liquid phases realized in a Rydberg-atom simulator.
- Iris Cong
- , Nishad Maskara
- & Mikhail D. Lukin
-
Article
| Open AccessNavigating the 16-dimensional Hilbert space of a high-spin donor qudit with electric and magnetic fields
Qudits, higher-dimensional analogues of qubits, expand quantum state space for information processing using fewer physical units. Here the authors demonstrate control over a 16-dimensional Hilbert space, equivalent to four qubits, using combined electron-nuclear states of a single Sb donor atom in Si.
- Irene Fernández de Fuentes
- , Tim Botzem
- & Andrea Morello
-
Article
| Open AccessSpin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe
Electron charge and spin shuttling is a promising technique for connecting distant spin qubits. Here the authors use conveyor-mode shuttling to achieve high-fidelity transport of a single electron spin in Si/SiGe by separation and rejoining of two spin-entangled electrons across a shuttling distance of 560 nm.
- Tom Struck
- , Mats Volmer
- & Lars R. Schreiber
-
Article
| Open AccessStrong coupling between a microwave photon and a singlet-triplet qubit
By coupling a spin-qubit to a superconducting resonator, remote spin-entanglement becomes feasible. Here, Ungerer et al achieve strong coupling between a superconducting resonator and a singlet-triplet spin qubit, in an InAs nanowire.
- J. H. Ungerer
- , A. Pally
- & C. Schönenberger
-
Article
| Open AccessRapid exchange cooling with trapped ions
Trapped ion quantum systems based on sympathetic cooling use ions of different species. Here the authors demonstrate exchange cooling using two ions of the same species (40Ca+) by taking advantage of the exchange of energy when the ions are brought close together.
- Spencer D. Fallek
- , Vikram S. Sandhu
- & Kenton R. Brown
-
Article
| Open AccessApproaching a fully-polarized state of nuclear spins in a solid
Highly polarized nuclear spins can supress decoherence of electron spin qubits, but this requires near-unity polarization. Here the authors implement a protocol combining optical excitation and fast carrier tunnelling to achieve nuclear spin polarizations above 95% in GaAs quantum dots on a timescale of 1 minute.
- Peter Millington-Hotze
- , Harry E. Dyte
- & Evgeny A. Chekhovich
-
Article
| Open AccessImproved machine learning algorithm for predicting ground state properties
Recent work proposed a machine learning algorithm for predicting ground state properties of quantum many-body systems that outperforms any non-learning classical algorithm but requires extensive training data. Lewis et al. present an improved algorithm with exponentially reduced training data requirements.
- Laura Lewis
- , Hsin-Yuan Huang
- & John Preskill
-
Article
| Open AccessTowards provably efficient quantum algorithms for large-scale machine-learning models
It is still unclear whether and how quantum computing might prove useful in solving known large-scale classical machine learning problems. Here, the authors show that variants of known quantum algorithms for solving differential equations can provide an advantage in solving some instances of stochastic gradient descent dynamics.
- Junyu Liu
- , Minzhao Liu
- & Liang Jiang
-
Article
| Open AccessPractical Hamiltonian learning with unitary dynamics and Gibbs states
Efficient characterisation of quantum many-body Hamiltonians has important applications for benchmarking NISQ devices. Here, the authors propose a method employing Chebyshev regression to learn the full Hamiltonian of a quantum system, with a sample complexity that scales efficiently with the system size.
- Andi Gu
- , Lukasz Cincio
- & Patrick J. Coles
-
Article
| Open AccessEfficient and robust estimation of many-qubit Hamiltonians
Learning Hamiltonians or Lindbladians of quantum systems from experimental data is important for characterization of interactions and noise processes in quantum devices. Here the authors propose an efficient protocol based on estimating time derivatives using multiple temporal sampling points and robust polynomial interpolation.
- Daniel Stilck França
- , Liubov A. Markovich
- & Johannes Borregaard
-
Article
| Open AccessRealization of a crosstalk-avoided quantum network node using dual-type qubits of the same ion species
In ion-photon quantum network platforms, usually memory qubits and communication qubits are encoded in ions of different species. Here, instead, the authors show how to realise ion-photon entanglement within the same-species-dual-encoding scheme.
- L. Feng
- , Y.-Y. Huang
- & L.-M. Duan
-
Article
| Open AccessSynergistic pretraining of parametrized quantum circuits via tensor networks
Scalable training of parametrised quantum circuit approaches is usually hindered by the barren plateau issue. Here, the authors show how initializing parametrised quantum circuits starting from scalable tensor-network based algorithms could ameliorate the problem.
- Manuel S. Rudolph
- , Jacob Miller
- & Alejandro Perdomo-Ortiz
-
Article
| Open AccessRemote transport of high-dimensional orbital angular momentum states and ghost images via spatial-mode-engineered frequency conversion
Remote transport of high-dimensional-encoded photonic states could in principle be achieved via quantum teleportation, but with considerable experimental effort. Here, instead, the authors exploit spatial-mode engineered frequency conversion between a coherent wave packet and a single photon to remotely transfer the HD OAM states, also providing a strategy for quantum imaging.
- Xiaodong Qiu
- , Haoxu Guo
- & Lixiang Chen
-
Article
| Open AccessThe two-qubit singlet/triplet measurement is universal for quantum computing given only maximally-mixed initial states
It has been conjectured that an alternative model of quantum computation—in which one only applies two-qubit singlet-vs-triplet measurements to almost any source of input qubits—is as powerful as the usual gate-based model. Here, the authors prove this conjecture, ending up with a model where computations are independent from the way in which one picks the axes of the Bloch sphere.
- Terry Rudolph
- & Shashank Soyuz Virmani
-
Article
| Open AccessHolographic codes from hyperinvariant tensor networks
The quantum error-correcting codes formed by tensor network models of holography have so far failed to produce the expected correlation functions in the boundary states. Here, the authors fill this gap by modifying a previously proposed model of hyperinvariant tensor networks.
- Matthew Steinberg
- , Sebastian Feld
- & Alexander Jahn
-
Article
| Open AccessRealizing a deep reinforcement learning agent for real-time quantum feedback
Real-time feedback control of quantum systems without relying on a description of the system itself is usually challenging. Here, the authors exploit deep reinforcement learning to realise feedback control for initialisation of a superconducting qubit on a submicrosecond timescale.
- Kevin Reuer
- , Jonas Landgraf
- & Christopher Eichler
-
Article
| Open AccessExperimental realisation of multi-qubit gates using electron paramagnetic resonance
Molecular electron spins are promising qubit candidates, however physical implementation of quantum gates is challenging. Little et al. explore the implementation of two-qubit entangling gates between nitroxide spin centres by pulsed electron paramagnetic resonance, building on NMR quantum computing protocols.
- Edmund J. Little
- , Jacob Mrozek
- & Richard E. P. Winpenny
-
Article
| Open AccessQuantum storage of entangled photons at telecom wavelengths in a crystal
Storage of photon entanglement at telecommunication wavelength is an important milestone for the development of the quantum internet. Here, the authors demonstrate storage and retrieval of entangled telecom photons—generated through SWFM in a silicon nitride microring resonator—in an Erbium doped crystal.
- Ming-Hao Jiang
- , Wenyi Xue
- & Xiao-Song Ma
-
Article
| Open AccessThe squeezed dark nuclear spin state in lead halide perovskites
Nuclear spins in solid-state systems present a promising platform for quantum information applications. Here the authors report evidence of the long-predicted entangled dark nuclear spin state via optical polarization of localized hole spins coupled to the nuclear bath in a lead halide perovskite semiconductor.
- E. Kirstein
- , D. S. Smirnov
- & M. Bayer
-
Article
| Open AccessFast generation of Schrödinger cat states using a Kerr-tunable superconducting resonator
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 AccessThe complexity of NISQ
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 AccessEngineering the formation of spin-defects from first principles
Spin defects in semiconductors are promising for quantum technologies but understanding of defect formation processes in experiment remains incomplete. Here the authors present a computational protocol to study the formation of spin defects at the atomic scale and apply it to the divacancy defect in SiC.
- Cunzhi Zhang
- , Francois Gygi
- & Giulia Galli