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  • Journal article
    Ruberti M, Averbukh V, 2023,

    Advances in modeling attosecond electron dynamics in molecular photoionization

    , WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE, ISSN: 1759-0876
  • Journal article
    Guo N-J, Li S, Liu W, Yang Y-Z, Zeng X-D, Yu S, Meng Y, Li Z-P, Wang Z-A, Xie L-K, Ge R-C, Wang J-F, Li Q, Xu J-S, Wang Y-T, Tang J-S, Gali A, Li C-F, Guo G-Cet al., 2023,

    Coherent control of an ultrabright single spin in hexagonal boron nitride at room temperature.

    , Nat Commun, Vol: 14

    Hexagonal boron nitride (hBN) is a remarkable two-dimensional (2D) material that hosts solid-state spins and has great potential to be used in quantum information applications, including quantum networks. However, in this application, both the optical and spin properties are crucial for single spins but have not yet been discovered simultaneously for hBN spins. Here, we realize an efficient method for arraying and isolating the single defects of hBN and use this method to discover a new spin defect with a high probability of 85%. This single defect exhibits outstanding optical properties and an optically controllable spin, as indicated by the observed significant Rabi oscillation and Hahn echo experiments at room temperature. First principles calculations indicate that complexes of carbon and oxygen dopants may be the origin of the single spin defects. This provides a possibility for further addressing spins that can be optically controlled.
  • Journal article
    Grell G, Guo Z, Driver T, Decleva P, Plesiat E, Picon A, Gonzalez-Vazquez J, Walter P, Marangos JP, Cryan JP, Marinelli A, Palacios A, Martin Fet al., 2023,

    Effect of the shot-to-shot variation on charge migration induced by sub-fs x-ray free-electron laser pulses

    , PHYSICAL REVIEW RESEARCH, Vol: 5
  • Journal article
    Yang Y-Z, Zhu T-X, Li Z-P, Zeng X-D, Guo N-J, Yu S, Meng Y, Wang Z-A, Xie L-K, Zhou Z-Q, Li Q, Xu J-S, Gao X-Y, Liu W, Wang Y-T, Tang J-S, Li C-F, Guo G-Cet al., 2023,

    Laser Direct Writing of Visible Spin Defects in Hexagonal Boron Nitride for Applications in Spin-Based Technologies

    , ACS Applied Nano Materials, Vol: 6, Pages: 6407-6414, ISSN: 2574-0970
  • Journal article
    Coste N, Gundin M, Fioretto DA, Thomas SE, Millet C, Mehdi E, Somaschi N, Morassi M, Pont M, Lemaitre A, Belabas N, Krebs O, Lanco L, Senellart Pet al., 2023,

    Probing the dynamics and coherence of a semiconductor hole spin via acoustic phonon-assisted excitation

    , QUANTUM SCIENCE AND TECHNOLOGY, Vol: 8, ISSN: 2058-9565
  • Journal article
    Shah R, Barrett TJ, Colcelli A, Orucevic F, Trombettoni A, Krueger Pet al., 2023,

    Probing the Degree of Coherence through the Full 1D to 3D Crossover

    , PHYSICAL REVIEW LETTERS, Vol: 130, ISSN: 0031-9007
  • Journal article
    Cheng C, Frasinski LJ, Mogol G, Allum F, Howard AJ, Rolles D, Bucksbaum PH, Brouard M, Forbes R, Weinacht Tet al., 2023,

    Multiparticle Cumulant Mapping for Coulomb Explosion Imaging

    , PHYSICAL REVIEW LETTERS, Vol: 130, ISSN: 0031-9007
  • Journal article
    Haug T, Self CN, Kim MS, 2023,

    Quantum machine learning of large datasets using randomized measurements

    , Machine Learning: Science and Technology, Vol: 4, Pages: 1-17, ISSN: 2632-2153

    Quantum computers promise to enhance machine learning for practical applications. Quantum machine learning for real-world data has to handle extensive amounts of high-dimensional data. However, conventional methods for measuring quantum kernels are impractical for large datasets as they scale with the square of the dataset size. Here, we measure quantum kernels using randomized measurements. The quantum computation time scales linearly with dataset size and quadratic for classical post-processing. While our method scales in general exponentially in qubit number, we gain a substantial speed-up when running on intermediate-sized quantum computers. Further, we efficiently encode high-dimensional data into quantum computers with the number of features scaling linearly with the circuit depth. The encoding is characterized by the quantum Fisher information metric and is related to the radial basis function kernel. Our approach is robust to noise via a cost-free error mitigation scheme. We demonstrate the advantages of our methods for noisy quantum computers by classifying images with the IBM quantum computer. To achieve further speedups we distribute the quantum computational tasks between different quantum computers. Our method enables benchmarking of quantum machine learning algorithms with large datasets on currently available quantum computers.
  • Journal article
    Lee C, Webster SC, Toba JM, Corfield O, Porter G, Thompson RCet al., 2023,

    Measurement-based ground-state cooling of a trapped-ion oscillator

    , Physical Review A: Atomic, Molecular and Optical Physics, Vol: 107, ISSN: 1050-2947

    Measurement-based cooling is a method by which a quantum system, initially in a thermal state, can beprepared probabilistically in its ground state through some sort of measurement. This is done by making ameasurement that heralds the system being in the desired state. Here we demonstrate the application of ameasurement-based cooling technique to a trapped atomic ion. The ion is precooled by Doppler laser coolingto a thermal state with a mean excitation of ¯n ≈ 18 and the measurement-based cooling technique selects thoseoccasions when the ion happens to be in the motional ground state. The fidelity of the heralding process is greaterthan 95%. This technique could be applied to other systems that are not as amenable to laser cooling as trappedions.
  • Journal article
    Thomas SE, Sagona-Stophel S, Schofield Z, Walmsley IA, Ledingham PMet al., 2023,

    Single-photon-compatible telecommunications-band quantum memory in a hot atomic gas

    , Physical Review Applied, Vol: 19, Pages: 1-6, ISSN: 2331-7019

    The efficient storage and on-demand retrieval of quantum optical states that are compatible with the telecommunications band is a requirement for future terrestrial-based quantum optical networking. Spectrum in the telecommunications band minimizes optical fiber-propagation losses, and broad optical bandwidth facilitates high-speed networking protocols. Here we report on a telecommunications-wavelength- and bandwidth-compatible quantum memory. Using the Off-Resonant Cascaded Absorption protocol in hot 87Rb vapor, we demonstrate a total internal memory efficiency of 20.90(1)% with a Doppler-limited storage time of 1.10(2) ns. We characterize the memory performance with weak coherent states and measure a signal-to-noise ratio of 1.9(1)×104 for an average input photon number of 0.084.
  • Journal article
    Birrittella RJ, Alsing PM, Schneeloch J, Gerry CC, Mimih J, Knight PLet al., 2023,

    Engineering superpositions of N00N states using an asymmetric non-linear Mach-Zehnder interferometer

    , AVS QUANTUM SCIENCE, Vol: 5
  • Journal article
    Ho C, Lim J, Sauer B, Tarbutt Met al., 2023,

    Measuring the nuclear magnetic quadrupole moment in heavy polar molecules

    , Frontiers in Physics, Vol: 11, Pages: 1-10, ISSN: 2296-424X

    Theories that extend the Standard Model of particle physics often introduce new interactions that violate charge-parity (CP) symmetry. CP-violating effects within an atomic nucleus can be probed by measuring its nuclear magnetic quadrupole moment (MQM). The sensitivity of such a measurement is enhanced when using a heavy polar molecule containing a nucleus with quadrupole deformation. We determine how the energy levels of a molecule are shifted by the MQM and how those shifts can be measured. The measurement scheme requires molecules in a superposition of magnetic sub-levels that differ by many units of angular momentum. We develop a generic scheme for preparing these states. Finally, we consider the sensitivity that can be reached, showing that this method can reduce the current uncertainties on several CP-violating parameters.
  • Journal article
    Lee J, Park J, Kim J, Kim MS, Nha Het al., 2023,

    Non-Gaussian entanglement criteria for atomic homodyne detection

    , Physical Review A, Vol: 107, ISSN: 2469-9926

    Homodyne measurement is a crucial tool widely used to address continuous variables for bosonic quantum systems. While an ideal homodyne detection provides a powerful analysis, e.g., to effectively measure quadrature amplitudes of light in quantum optics, it relies on the use of a strong reference field, the so-called local oscillator, typically in a coherent state. Such a strong coherent local oscillator may not be readily available, particularly for a massive quantum system like a Bose-Einstein condensate, posing a substantial challenge in dealing with continuous variables appropriately. It is necessary to establish a practical framework that includes the effects of nonideal local oscillators for a rigorous assessment of various quantum tests and applications. We here develop entanglement criteria beyond a Gaussian regime applicable for this realistic homodyne measurement that do not require assumptions on the state of local oscillators. We discuss the working conditions of homodyne detection to effectively detect non-Gaussian quantum entanglement under various states of local oscillators.
  • Journal article
    Hofsaess S, Padilla-Castillo JE, Wright SC, Kray S, Thomas R, Sartakov BG, Ohayon B, Meijer G, Truppe Set al., 2023,

    High-resolution isotope-shift spectroscopy of Cd I

    , PHYSICAL REVIEW RESEARCH, Vol: 5
  • Conference paper
    Sun B, Sotirova A, Dela Cruz V, Ballance C, Mer E, Patel RB, Walmsley IA, Booth MJet al., 2023,

    Ultrafast Laser Written Waveguide Chips for Quantum Applications

    Ultrafast laser micro-fabrication has found a wide range of applications in the past decades. In particular, it is possible to create advanced photonics chips based on three-dimensional optical waveguides. Significant potential has been demonstrated in areas such as topological photonics[1] and quantum technologies[2]. Traditional fabrication methods create optical waveguides by focusing ultrafast laser into transparent materials, such as fused silica or borosilicate glass, producing localized refractive index modification. Here, we demonstrate that our recently reported Spherical Phase Induced Multi-Core Waveguides (SPIM-WGs)[3] overcome some constraints of traditional waveguide fabrication techniques, enabling new functionalities in quantum applications.
  • Conference paper
    Pearce E, Flórez J, Gemmell NR, Karzazi MA, Ma Y, Bressanini G, Battle RA, Murray RT, Kim MS, Phillips CC, Oulton RF, Clark ASet al., 2023,

    Enhancing Nonlinear Interferometers for Imaging with Undetected Photons: Seeding and High-Gain

    Infrared (IR) imaging and spectroscopy is invaluable to many disciplines for its ability to probe molecular responses, from material analysis to diagnostic medicine. However, these applications are often limited by inefficient, noisy detectors. Non-degenerate nonlinear interferometers (NLIs) offer an alternative route through a technique known as imaging with undetected photons [1]. For an NLI producing visible-IR photon pairs, a change in the IR due to an object can be observed as a change to the interference of the visible photons. The IR does not need to be detected, bypassing the need for IR detectors completely.
  • Conference paper
    Thomas SE, Wagner L, Joos R, Sittig R, Nawrath C, Burdekin P, De Buy Wenniger IM, Rasiah MJ, Huber-Loyol T, Sagona-Stophe S, Höfling S, Jetter M, Michler P, Walmsley IA, Portalupi SL, Ledingham PMet al., 2023,

    Deterministic Storage and Retrieval of Telecom Light from a Quantum Dot Single-Photon Source Interfaced with an Atomic Quantum Memory

    We demonstrate deterministic storage and retrieval of light from a semiconductor quantum dot single-photon source in an atomic ensemble quantum memory at telecommunications wavelengths, which is a long sought-after goal in photonic quantum technologies.
  • Conference paper
    Szuniewicz J, Sagona-Stophel S, Thomas S, Walmsley I, Karpin Met al., 2023,

    Phase-noise-insensitive orthogonality verification of single-photon-level temporal modes

    Photonic quantum technologies are a rapidly developing field. We seek new ways for storing more information in a single photon. One of the promising ways for multidimensional storage is using temporal modes of single photons (either time-bin or structured modes such as Hermitte-Gaussian modes) enabling us to send more information per photon using their theoretically unlimited dimensionality [1,2]. Moreover, temporal modes offer high stability, ease of detection and creation.
  • Conference paper
    Wursten EJ, Borchert MJ, Devlin JA, Erlewein SR, Fleck M, Harrington JA, Jäger JI, Latacz BM, Micke P, Umbrazunas G, Abbass F, Bohman M, Kommu S, Popper D, Wiesinger M, Will C, Yildiz H, Blaum K, Matsuda Y, Mooser A, Ospelkaus C, Soter A, Quint W, Walz J, Yamazaki Y, Smorra C, Ulmer Set al., 2023,

    Testing CPT Invariance by High-Precision Comparisons of Fundamental Properties of Protons and Antiprotons at BASE

    , Pages: 1-5

    The BASE collaboration at the Antiproton Decelerator facility of CERN compares the fundamental properties of protons and antiprotons using advanced Penning-trap systems. In previous measurement campaigns, we measured the magnetic moments of the proton and the antiproton, reaching (sub-)parts-in-a-billion fractional uncertainty. In the latest campaign, we have compared the proton and antiproton charge-to-mass ratios with a fractional uncertainty of 16 parts in a trillion. In this contribution, we give an overview of the measurement campaign, and detail how its results are used to constrain nine spin-independent coefficients of the Standard-Model Extension in the proton and electron sector.
  • Journal article
    Haug T, Kim M, 2023,

    Scalable measures of magic for quantum computers

    , PRX Quantum, Vol: 4, ISSN: 2691-3399

    Nonstabilizerness or magic resource characterizes the amount of non-Clifford operations needed to prepare quantum states. It is a crucial resource for quantum computing and a necessary condition for quantum advantage. However, quantifying magic resource beyond a few qubits has been a major challenge. Here, we introduce efficient measures of magic resource for pure quantum states with a sampling cost that is independent of the number of qubits. Our method uses Bell measurements over two copies of a state, which we implement in experiment together with a cost-free error-mitigation scheme. We show the transition of classically simulable stabilizer states into intractable quantum states on the IonQ quantum computer. For applications, we efficiently distinguish stabilizer and nonstabilizer states with low measurement cost even in the presence of experimental noise. Further, we propose a variational quantum algorithm to maximize our measure via the shift rule. Our algorithm can be free of barren plateaus even for highly expressible variational circuits. Finally, we experimentally demonstrate a Bell-measurement protocol for the stabilizer Rényi entropy as well as the Wallach-Meyer entanglement measure. Our results pave the way to understanding the nonclassical power of quantum computers, quantum simulators, and quantum many-body systems.
  • Book chapter
    James DFV, Knight PL, Scheel S, 2023,

    Quantum Information

    , Springer Handbooks, Pages: 1259-1271

    Since its inception over a century ago, quantum mechanics has been an indispensable tool for understanding atomic structure and has been used very successfully in the calculation energy levels, natural lifetimes, and cross sections; but for the most part, the philosophical interpretation of quantum mechanics has been left to others. However, after the work of Bell in the 1960s showed that the peculiarly nonlocal nature of quantum correlations could be tested in the lab, a number of atomic physicists turned to the experimental study of entanglement and quantum measurement. By the mid 1990s, it was becoming increasingly apparent that the peculiar quantum correlations and quantum superpositions might be exploited in quantum information processing, and that practical devices to exploit this potential might well be within the grasp of current experimental techniques. This led to an explosive growth of the subject over the past 25 years, fueled by the long-term prospects of quantum computing, quantum-enhanced metrology, and quantum cryptography. Today, quantum information is a vast area, embracing physics, chemistry, electrical engineering, material science, mathematics, and computer science. In this chapter, we introduce some of the basics of the subject, with an emphasis on atomic, molecular, and optical physics.
  • Journal article
    Alexander OG, Marangos JP, Ruberti M, Vacher Met al., 2023,

    Attosecond electron dynamics in molecular systems

    , Advances in Atomic Molecular and Optical Physics, Vol: 72, Pages: 183-251, ISSN: 1049-250X

    In this paper we review the topic of attosecond electron dynamics in molecular systems. We present a digest of recent research on this topic conducted by ourselves and other researchers with the intention of providing an accessible, but rigorous, account of the current state of this intriguing field of research. A short account of the background quantum theory is given before discussing recent theoretical advances on understanding correlation driven electron dynamics and electron nuclear coupling in molecules undergoing fast photoionization. We then review experimental advances, using both high harmonic generation and XFEL based ultrafast x-ray pulses, and provide three recent case studies from our own work to illustrate this. The final sections look forward to the next steps in this field: we discuss the prospect for controlling attochemistry as well as extending attosecond measurement methods to electron dynamics in larger molecules and condensed phase systems.
  • Journal article
    Hanks M, Kim MS, 2022,

    Fault tolerance in qudit circuit design

    , PHYSICAL REVIEW A, Vol: 106, ISSN: 2469-9926
  • Journal article
    Fasoulakis A, Major KDD, Hoggarth RAA, Burdekin P, Bogusz DPP, Schofield RCC, Clark ASSet al., 2022,

    Uniaxial strain tuning of organic molecule single photon sources

    , NANOSCALE, Vol: 15, Pages: 177-184, ISSN: 2040-3364
  • Journal article
    Raii O, Mintert F, Burgarth D, 2022,

    Scalable quantum control and non-Abelian anyon creation in the Kitaev honeycomb model

    , PHYSICAL REVIEW A, Vol: 106, ISSN: 2469-9926
  • Journal article
    Ohayon B, Hofsaess S, Padilla-Castillo JE, Wright SC, Meijer G, Truppe S, Gibble K, Sahoo BKet al., 2022,

    Isotope shifts in cadmium as a sensitive probe for physics beyond the standard model

    , NEW JOURNAL OF PHYSICS, Vol: 24, ISSN: 1367-2630
  • Journal article
    Alonso I, Alpigiani C, Altschul B, Araujo H, Arduini G, Arlt J, Badurina L, Balaz A, Bandarupally S, Barish BC, Barone M, Barsanti M, Bass S, Bassi A, Battelier B, Baynham CFA, Beaufils Q, Berge J, Bernabeu J, Bertoldi A, Bingham R, Bize S, Blas D, Bongs K, Bouyer P, Braitenberg C, Brand C, Braxmaier C, Bresson A, Buchmueller O, Budker D, Bugalho L, Burdin S, Cacciapuoti L, Callegari S, Calmet X, Calonico D, Canuel B, Caramete L-I, Carraz O, Cassettari D, Chakraborty P, Chattopadhyay S, Chauhan U, Chen X, Chen Y-A, Chiofalo ML, Coleman J, Corgier R, Cotter JP, Cruise AM, Cui Y, Davies G, De Roeck A, Demarteau M, Derevianko A, Di Clemente M, Djordjevic GS, Donadi S, Dore O, Dornan P, Doser M, Drougakis G, Dunningham J, Easo S, Eby J, Elertas G, Ellis J, Evans D, Examilioti P, Fadeev P, Fani M, Fassi F, Fattori M, Fedderke MA, Felea D, Feng C-H, Ferreras J, Flack R, Flambaum VV, Forsberg R, Fromhold M, Gaaloul N, Garraway BM, Georgousi M, Geraci A, Gibble K, Gibson V, Gill P, Giudice G, Goldwin J, Gould O, Grachov O, Graham PW, Grasso D, Griffin P, Guerlin C, Gupta RK, Haehnelt M, Hawkins L, Hees A, Henderson VA, Herr W, Herrmann S, Hird T, Hobson R, Hock V, Hogan JM, Holst B, Holynski M, Israelsson U, Jeglic P, Jetzer P, Juzeliunas G, Kaltenbaek R, Kamenik JF, Kehagias A, Kirova T, Kiss-Toth M, Koke S, Kolkowitz S, Kornakov G, Kovachy T, Krutzik M, Kumar M, Kumar P, Lammerzahl C, Landsberg G, Le Poncin-Lafitte C, Leibrandt DR, Leveque T, Lewicki M, Li R, Lipniacka A, Lisdat C, Liu M, Lopez-Gonzalez JL, Loriani S, Louko J, Luciano GG, Lundblad N, Maddox S, Mahmoud MA, Maleknejad A, March-Russell J, Massonnet D, McCabe C, Meister M, Meznarsic T, Micalizio S, Migliaccio F, Millington P, Milosevic M, Mitchell J, Morley GW, Muller J, Murphy E, Mustecaplioglu OE, O'Shea V, Oi DKL, Olson J, Pal D, Papazoglou DG, Pasatembou E, Paternostro M, Pawlowski K, Pelucchi E, dos Santos FP, Peters A, Pikovski I, Pilaftsis A, Pinto A, Prevedelli M, Puthiya-Veettil V, Quenby J, Rafelskiet al., 2022,

    Cold atoms in space: community workshop summary and proposed road-map

    , EPJ QUANTUM TECHNOLOGY, Vol: 9, ISSN: 2662-4400
  • Journal article
    Haug T, Kim MS, 2022,

    Natural parametrized quantum circuit

    , PHYSICAL REVIEW A, Vol: 106, ISSN: 2469-9926
  • Journal article
    Barnard J, Lee J, Alexander O, Jarosch S, Garratt D, Picciuto R, Kowalczyk K, Ferchaud C, Gregory A, Matthews M, Marangos Jet al., 2022,

    Delivery of stable ultra-thin liquid sheets in vacuum for biochemical spectroscopy

    , Frontiers in Molecular Biosciences, Vol: 9, ISSN: 2296-889X

    The development of ultra-thin flat liquid sheets capable of running in vacuum has provided an exciting new target for X-ray absorption spectroscopy in the liquid and solution phases. Several methods have become available for delivering in-vacuum sheet jets using different nozzle designs. We compare the sheets produced by two different types of nozzle; a commercially available borosillicate glass chip using microfluidic channels to deliver colliding jets, and an in-house fabricated fan spray nozzle which compresses the liquid on an axis out of a slit to achieve collision conditions. We find in our tests that both nozzles are suitable for use in X-ray absorption spectroscopy with the fan spray nozzle producing thicker but more stable jets than the commercial nozzle. We also provide practical details of how to run these nozzles in vacuum.
  • Journal article
    Schwickert D, Ruberti M, Kolorenc P, Przystawik A, Skruszewicz S, Sumfleth M, Braune M, Bocklage L, Carretero L, Czwalinna MK, Diaman D, Duesterer S, Kuhlmann M, Palutke S, Roehlsberger R, Roensch-Schulenburg J, Toleikis S, Usenko S, Viefhaus J, Vorobiov A, Martins M, Kip D, Averbukh V, Marangos JP, Laarmann Tet al., 2022,

    Charge-induced chemical dynamics in glycine probed with time-resolved Auger electron spectroscopy

    , STRUCTURAL DYNAMICS-US, Vol: 9

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