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  • Journal article
    Wright SC, Doppelbauer M, Hofsass S, Schewe HC, Sartakov B, Meijer G, Truppe Set al., 2023,

    Cryogenic buffer gas beams of AlF, CaF, MgF, YbF, Al, Ca, Yb and NO - a comparison

    , MOLECULAR PHYSICS, Vol: 121, ISSN: 0026-8976
  • Journal article
    Hajivassiliou G, Kassapis M, Tisch JWG, 2023,

    Rapid retrieval of femtosecond and attosecond pulses from streaking traces using convolutional neural networks

    , New Journal of Physics, Vol: 25, ISSN: 1367-2630

    Attosecond streaking is a powerful and versatile technique that allows the full-field characterisation of femtosecond to attosecond optical pulses. It has been instrumental in the verification of attosecond pulse generation and probing of ultrafast dynamics in matter. Recently, machine learning (ML) has been applied to retrieve the fields from streaking data (White and Chang 2019 Opt. Express27 4799; Zhu et al 2020 Sci. Rep.10 5782; Brunner et al 2022 Opt. Express30 15669–84). This offers a number of advantages compared with traditional iterative algorithms, including faster processing and better resilience to noise. Here, we implement a ML approach based on convolutional neural networks and limit the search to physically realistic pulses that can be specified with a small number of parameters. This leads to substantial reductions in both training and retrieval times, enabling near kHz retrieval rates. We examine how the retrieval performance is affected by noise, and for the first time in this context, study the effect of missing data. We show that satisfactory retrievals are still possible with signal to noise ratios as low as 10, and with up to $40\%$ of data missing.
  • Journal article
    Engel RY, Alexander O, Atak K, Bovensiepen U, Buck J, Carley R, Cascella M, Chardonnet V, Chiuzbaian GS, David C, Doring F, Eschenlohr A, Gerasimova N, de Groot F, Le Guyader L, Humphries OS, Izquierdo M, Jal E, Kubec A, Laarmann T, Lambert C-H, Luening J, Marangos JP, Mercadier L, Mercurio G, Miedema PS, Ollefs K, Pfau B, Rosner B, Rossnagel K, Rothenbach N, Scherz A, Schlappa J, Scholz M, Schunck JO, Setoodehnia K, Stamm C, Techert S, Vinko SM, Wende H, Yaroslavtsev AA, Yin Z, Beye Met al., 2023,

    Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser

    , STRUCTURAL DYNAMICS-US, Vol: 10
  • Journal article
    Mukherjee B, Frye MD, Le Sueur CR, Tarbutt MR, Hutson JMet al., 2023,

    Shielding collisions of ultracold CaF molecules with static electric fields

    , Physical Review Research, Vol: 5, ISSN: 2643-1564

    We study collisions of ultracold CaF molecules in strong static electric fields. These fields allow the creationof long-range barriers in the interaction potential, effectively preventing the molecules from reaching theshort-range region where inelastic and other loss processes are likely to occur. We carry out coupled-channelcalculations of rate coefficients for elastic scattering and loss. We develop an efficient procedure for includingenergetically well-separated rotor functions in the basis set via a Van Vleck transformation. We show thatshielding is particularly efficient for CaF and allows the rate of two-body loss processes to be reduced by a factorof 107 or more at a field of 23 kV/cm. The loss rates remain low over a substantial range of fields. Electron andnuclear spins cause strong additional loss in some small ranges of field, but have little effect elsewhere. Theseresults pave the way for evaporative cooling of CaF towards quantum degeneracy
  • Journal article
    Hutchison CDM, Baxter JM, Fitzpatrick A, Dorlhiac G, Fadini A, Perrett S, Maghlaoui K, Lefevre SB, Cordon-Preciado V, Ferreira JL, Chukhutsina VU, Garratt D, Barnard J, Galinis G, Glencross F, Morgan RM, Stockton S, Taylor B, Yuan L, Romei MG, Lin C-Y, Marangos JP, Schmidt M, Chatrchyan V, Buckup T, Morozov D, Park J, Park S, Eom I, Kim M, Jang D, Choi H, Hyun H, Park G, Nango E, Tanaka R, Owada S, Tono K, DePonte DP, Carbajo S, Seaberg M, Aquila A, Boutet S, Barty A, Iwata S, Boxer SG, Groenhof G, van Thor JJet al., 2023,

    Optical control of ultrafast structural dynamics in a fluorescent protein

    , NATURE CHEMISTRY, ISSN: 1755-4330
  • Journal article
    Orozco-Ruiz M, Simsek S, Kulmiya SA, Hile SJ, Hensinger WK, Mintert Fet al., 2023,

    Optimal control with a multidimensional quantum invariant

    , PHYSICAL REVIEW A, Vol: 108, ISSN: 2469-9926
  • Journal article
    Clarke J, Neveu P, Khosla KE, Verhagen E, Vanner MRet al., 2023,

    Cavity quantum optomechanical nonlinearities and position measurement beyond the breakdown of the linearized approximation

    , Physical Review Letters, Vol: 131, ISSN: 0031-9007

    Several optomechanics experiments are now entering the highly sought nonlinear regime where optomechanical interactions are large even for low light levels. Within this regime, new quantum phenomena and improved performance may be achieved; however, a corresponding theoretical formalism of cavity quantum optomechanics that captures the nonlinearities of both the radiation-pressure interaction and the cavity response is needed to unlock these capabilities. Here, we develop such a nonlinear cavity quantum optomechanical framework, which we then utilize to propose how position measurement can be performed beyond the breakdown of the linearized approximation. Our proposal utilizes optical general-dyne detection, ranging from single to dual homodyne, to obtain mechanical position information imprinted onto both the optical amplitude and phase quadratures and enables both pulsed and continuous modes of operation. These cavity optomechanical nonlinearities are now being confronted in a growing number of experiments, and our framework will allow a range of advances to be made in, e.g., quantum metrology, explorations of the standard quantum limit, and quantum measurement and control.
  • Journal article
    Thekkadath G, England D, Bouchard F, Zhang Y, Kim M, Sussman Bet al., 2023,

    Intensity interferometry for holography with quantum and classical light

    , Science Advances, Vol: 9, ISSN: 2375-2548

    As first demonstrated by Hanbury Brown and Twiss, it is possible to observe interference between independent light sources by measuring correlations in their intensities rather than their amplitudes. In this work, we apply this concept of intensity interferometry to holography. We combine a signal beam with a reference and measure their intensity cross-correlations using a time-tagging single-photon camera. These correlations reveal an interference pattern from which we reconstruct the signal wavefront in both intensity and phase. We demonstrate the principle with classical and quantum light, including a single photon. Since the signal and reference do not need to be phase-stable nor from the same light source, this technique can be used to generate holograms of self-luminous or remote objects using a local reference, thus opening the door to new holography applications.
  • Journal article
    Driver T, Pipkorn R, Averbukh V, Frasinski LJJ, Marangos JPP, Edelson-Averbukh Met al., 2023,

    Identification of cofragmented combinatorial peptide isomers by two-dimensional partial covariance mass spectrometry

    , Journal of the American Society for Mass Spectrometry, Vol: 34, Pages: 1230-1234, ISSN: 1044-0305

    Combinatorial post-translational modifications (PTMs), such as those forming the so-called “histone code”, have been linked to cell differentiation, embryonic development, cellular reprogramming, aging, cancers, neurodegenerative disorders, etc. Nevertheless, a reliable mass spectral analysis of the combinatorial isomers represents a considerable challenge. The difficulty stems from the incompleteness of information that could be generated by the standard MS to differentiate cofragmented isomeric sequences in their naturally occurring mixtures based on the fragment mass-to-charge ratio and relative abundance information only. Here we show that fragment–fragment correlations revealed by two-dimensional partial covariance mass spectrometry (2D-PC-MS) allow one to solve the combinatorial PTM puzzles that cannot be tackled by the standard MS as a matter of principle. We introduce 2D-PC-MS marker ion correlation approach and demonstrate experimentally that it can provide the missing information enabling identification of cofragmentated combinatorially modified isomers. Our in silico study shows that the marker ion correlations can be used to unambiguously identify 5 times more cofragmented combinatorially acetylated tryptic peptides and 3 times more combinatorially modified Glu-C peptides of human histones than is possible using standard MS methods.
  • Journal article
    Bird RC, Tarbutt MR, Hutson JM, 2023,

    Tunable Feshbach resonances in collisions of ultracold molecules in ²∑ states with alkali-metal atoms

    , Physical Review Research, Vol: 5, ISSN: 2643-1564

    We consider the magnetically tunable Feshbach resonances that may exist in ultracold mixtures of moleculesin 2 states and alkali-metal atoms. We focus on Rb+CaF as a prototype system. There are likely to be Feshbachresonances analogous to those between pairs of alkali-metal atoms. We investigate the patterns of near-thresholdstates and the resonances that they cause, using coupled-channel calculations of the bound states and low-energyscattering on model interaction potentials. We explore the dependence of the properties on as-yet-unknownpotential parameters. There is a high probability that resonances will exist at magnetic fields below 1000 G,and that these will be broad enough to control collisions and form triatomic molecules by magnetoassociation.We consider the effects of CaF rotation and anisotropy of the interaction potential, and conclude that they mayproduce additional resonances but should not affect the existence of rotation-free resonances.
  • Journal article
    Chen W, Lu Y, Zhang S, Zhang K, Huang G, Qiao M, Su X, Zhang J, Zhang J-N, Banchi L, Kim MS, Kim Ket al., 2023,

    Scalable and programmable phononic network with trapped ions

    , Nature Physics, Vol: 19, Pages: 877-883, ISSN: 1745-2473

    A network of bosons evolving among different modes while passing through beam splitters and phase shifters has been applied to demonstrate quantum computational advantage. While such networks have mostly been implemented in optical systems using photons, alternative realizations addressing major limitations in photonic systems such as photon loss have been explored recently. Quantized excitations of vibrational modes (phonons) of trapped ions are a promising candidate to realize such bosonic networks. Here, we demonstrate a minimal-loss programmable phononic network in which any phononic state can be deterministically prepared and detected. We realize networks with up to four collective vibrational modes, which can be extended to reveal quantum advantage. We benchmark the performance of the network for an exemplary tomography algorithm using arbitrary multi-mode states with fixed total phonon number. We obtain high reconstruction fidelities for both single- and two-phonon states. Our experiment demonstrates a clear pathway to scale up a phononic network for quantum information processing beyond the limitations of classical and photonic systems.
  • Journal article
    Tarlton JE, Thompson RC, Lucas DM, 2023,

    Surface-electrode ion trap design for near-field microwave quantum gates

    , Applied Physics B: Lasers and Optics, Vol: 129, ISSN: 0721-7269

    We present a design study into an ion trap electrode geometry for applying near-field microwave two-qubit gates. This design features an ‘S’-shaped meander electrode to passively null the microwave field. It has ground planes separating the meander electrode from all of the DC and single-qubit microwave electrodes, which should reduce the sensitivity of the microwave field distribution to the boundary conditions of these electrodes. We show that it is possible to design a single-layer trap with this geometry such that the simulated microwave field null overlaps with the RF field null, and that the positions of these nulls can be simulated to a precision of 100 nm with moderate computing resources. We also show that such a trap can be designed such that ion chains can be trapped, transported and split with feasible DC and RF voltages. While this particular design is optimized for 43Ca+ ions, our approach could be applied to other ions by changing the microwave frequency tomatch the corresponding qubit transition frequency.
  • Journal article
    Ling Y, Qvarfort S, Mintert F, 2023,

    Fast optomechanical photon blockade

    , Physical Review Research, Vol: 5, Pages: 1-14, ISSN: 2643-1564

    The photon blockade effect is commonly exploited in the development of single-photon sources. While the photon blockade effect could be used to prepare high-fidelity single-photon states in idealized regimes, practical implementations in optomechanical systems suffer from an interplay of competing processes. Here we derive a control scheme that exploits destructive interference of Fock state amplitudes of more than one photon. The resulting preparation time for photon-blockaded quantum states is limited only by the optomechanical interaction strength and can thus be orders of magnitude shorter than in existing schemes that achieve photon blockade in the steady state.
  • Journal article
    Latacz BM, Arndt BP, Bauer BB, Devlin JA, Erlewein SR, Fleck M, Jaeger JI, Schiffelholz M, Umbrazunas G, Wursten EJ, Abbass F, Micke P, Popper D, Wiesinger M, Will C, Yildiz H, Blaum K, Matsuda Y, Mooser A, Ospelkaus C, Quint W, Soter A, Walz J, Yamazaki Y, Smorra C, Ulmer Set al., 2023,

    BASE-high-precision comparisons of the fundamental properties of protons and antiprotons

    , EUROPEAN PHYSICAL JOURNAL D, Vol: 77, ISSN: 1434-6060
  • Journal article
    Bergmann K, Eberly JH, Halfmann T, Knight PL, Vitanov NVet al., 2023,

    Editorial note for the J. Phys. B. special issue 'Coherent Control: Photons, Atoms and Molecules' honoring the life and work of Bruce W Shore

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 56, ISSN: 0953-4075
  • 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
    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.

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