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  • Journal article
    Wu Y, Huang Z, Sun J, Yuan X, Wang JB, Lv Det al., 2023,

    Orbital expansion variational quantum eigensolver

    , Quantum Science and Technology, Vol: 8, Pages: 045030-045030

    <jats:title>Abstract</jats:title> <jats:p>Variational quantum eigensolver (VQE) has emerged as a promising method for investigating ground state properties in quantum chemistry, materials science, and condensed matter physics. However, the conventional VQE method generally lacks systematic improvement and convergence guarantees, particularly when dealing with strongly correlated systems. In light of these challenges, we present a novel framework called orbital expansion VQE (OE-VQE) to address these limitations. The key idea is to devise an efficient convergence path by utilizing shallower quantum circuits, starting from a highly compact active space and gradually expanding it until convergence to the ground state is achieved. To validate the effectiveness of the OE-VQE framework, we conducted benchmark simulations on several small yet representative molecules, including the <jats:inline-formula> <jats:tex-math><?CDATA $\mathrm{H}_{6}$?></jats:tex-math> <mml:math xmlns:mml="" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="" xlink:href="qstacf9c7ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> chain, <jats:inline-formula> <jats:tex-math><?CDATA $\mathrm{H}_{10}$?></jats:tex-math> <mml:math xmln

  • Journal article
    Ruberti M, Averbukh V, 2023,

    Advances in modeling attosecond electron dynamics in molecular photoionization

    , Wiley Interdisciplinary Reviews: Computational Molecular Science, Vol: 13, ISSN: 1759-0876

    The dramatic progress of experimental attosecond science has called for the development of new theoretical and computational tools capable of accurately model the correlated electron dynamics triggered by attosecond molecular photoionization. We describe the nature and the main outcome of this development, with particular focus on the B-spline ADC and RCS-ADC ab initio methods. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods Software > Simulation Methods Theoretical and Physical Chemistry > Spectroscopy.

  • Journal article
    Hutchison CDM, Baxter JM, Fitzpatrick A, Dorlhiac G, Fadini A, Perrett S, Maghlaoui K, Lefèvre 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.

    , Nat Chem

    The photoisomerization reaction of a fluorescent protein chromophore occurs on the ultrafast timescale. The structural dynamics that result from femtosecond optical excitation have contributions from vibrational and electronic processes and from reaction dynamics that involve the crossing through a conical intersection. The creation and progression of the ultrafast structural dynamics strongly depends on optical and molecular parameters. When using X-ray crystallography as a probe of ultrafast dynamics, the origin of the observed nuclear motions is not known. Now, high-resolution pump-probe X-ray crystallography reveals complex sub-ångström, ultrafast motions and hydrogen-bonding rearrangements in the active site of a fluorescent protein. However, we demonstrate that the measured motions are not part of the photoisomerization reaction but instead arise from impulsively driven coherent vibrational processes in the electronic ground state. A coherent-control experiment using a two-colour and two-pulse optical excitation strongly amplifies the X-ray crystallographic difference density, while it fully depletes the photoisomerization process. A coherent control mechanism was tested and confirmed the wave packets assignment.

  • Journal article
    Vogwell J, Smirnova O, Rego L, Ayuso Molinero Det al., 2023,

    Ultrafast control over chiral sum-frequency generation

    , Science Advances, ISSN: 2375-2548

    We introduce an ultrafast all-optical approach for efficient chiral recognition which relies on the interference between two low-order nonlinear processes which are ubiquitous in nonlinear optics: sum-frequency generationand third-harmonic generation. In contrast to traditional sum-frequency generation, our approach encodes the medium’s handedness in the intensity of theemitted harmonic signal, rather than in its phase, and it enables full controlover the enantiosensitive response. We show how, by sculpting the sub-opticalcycle oscillations of the driving laser field, we can force one molecular enantiomer to emit bright light while its mirror twin remains dark, thus reachingthe ultimate efficiency limit of chiral sensitivity via low-order nonlinear lightmatter interactions. Our work paves the way for ultrafast and highly efficientimaging and control of the chiral electronic clouds of chiral molecules usinglasers with moderate intensities, in all states of matter: from gases to liquidsto solids, with molecular specificity and on ultrafast timescales.

  • Journal article
    Huang Y, Shao Y, Ren W, Sun J, Lv Det al., 2023,

    Efficient Quantum Imaginary Time Evolution by Drifting Real-Time Evolution: An Approach with Low Gate and Measurement Complexity

    , Journal of Chemical Theory and Computation, Vol: 19, Pages: 3868-3876, ISSN: 1549-9618
  • Journal article
    Driver T, Pipkorn R, Averbukh V, Frasinski LJ, Marangos JP, Edelson-Averbukh Met al., 2023,

    Identification of Cofragmented Combinatorial Peptide Isomers by Two-Dimensional Partial Covariance Mass Spectrometry.

    , J Am Soc Mass Spectrom, Vol: 34, Pages: 1230-1234

    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
    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 creation of long-range barriers in the interaction potential, effectively preventing the molecules from reaching the short-range region where inelastic and other loss processes are likely to occur. We carry out coupled-channel calculations of rate coefficients for elastic scattering and loss. We develop an efficient procedure for including energetically well-separated rotor functions in the basis set via a Van Vleck transformation. We show that shielding is particularly efficient for CaF and allows the rate of two-body loss processes to be reduced by a factor of 107 or more at a field of 23 kV/cm. The loss rates remain low over a substantial range of fields. Electron and nuclear spins cause strong additional loss in some small ranges of field, but have little effect elsewhere. These results pave the way for evaporative cooling of CaF towards quantum degeneracy.

  • Journal article
    Rego L, Smirnova O, Ayuso Molinero D, 2023,

    Tilting light's polarization plane to spatially separate the ultrafast nonlinear response of chiral molecules

    , Nanophotonics, Vol: 12, Pages: 2873-2879, ISSN: 2192-8606

    Distinguishing between the left- and right-handed versions of a chiral molecule (enantiomers) is vital, but also inherently difficult. Traditional optical methods using elliptically/circularly polarized light rely on linear effects which arise beyond the electric-dipole approximation, posing major limitations for ultrafast spectroscopy. Here we show how to turn an ultrashort elliptical pulse into an efficient chiro-optical tool: by tilting its polarization plane towards its propagation direction. This forward tilt can be achieved by focusing the beam tightly, creating structured light which exhibits a nontrivial polarization pattern in space. Using state-of-the-art computational modelling, we show that our structured field realizes a near-field interferometer for efficient chiral recognition that separates the nonlinear optical response of left- and right-handed molecules in space. Our work provides a simple, yet highly efficient, way of spatially structuring the polarization of light to image molecular chirality, with extreme enantio-efficiency and on ultrafast time scales.

  • Journal article
    Yu W, Sun J, Han Z, Yuan Xet al., 2023,

    Robust and Efficient Hamiltonian Learning

    , Quantum, Vol: 7, Pages: 1045-1045

    <jats:p>With the fast development of quantum technology, the sizes of both digital and analog quantum systems increase drastically. In order to have better control and understanding of the quantum hardware, an important task is to characterize the interaction, i.e., to learn the Hamiltonian, which determines both static and dynamic properties of the system. Conventional Hamiltonian learning methods either require costly process tomography or adopt impractical assumptions, such as prior information on the Hamiltonian structure and the ground or thermal states of the system. In this work, we present a robust and efficient Hamiltonian learning method that circumvents these limitations based only on mild assumptions. The proposed method can efficiently learn any Hamiltonian that is sparse on the Pauli basis using only short-time dynamics and local operations without any information on the Hamiltonian or preparing any eigenstates or thermal states. The method has a scalable complexity and a vanishing failure probability regarding the qubit number. Meanwhile, it performs robustly given the presence of state preparation and measurement errors and resiliently against a certain amount of circuit and shot noise. We numerically test the scaling and the estimation accuracy of the method for transverse field Ising Hamiltonian with random interaction strengths and molecular Hamiltonians, both with varying sizes and manually added noise. All these results verify the robustness and efficacy of the method, paving the way for a systematic understanding of the dynamics of large quantum systems.</jats:p>

  • Journal article
    Cao C, Sun J, Yuan X, Hu H-S, Pham HQ, Lv Det al., 2023,

    Ab initio quantum simulation of strongly correlated materials with quantum embedding

    , npj Computational Materials, Vol: 9

    <jats:title>Abstract</jats:title><jats:p>Quantum computing has shown great potential in various quantum chemical applications such as drug discovery, material design, and catalyst optimization. Although significant progress has been made in the quantum simulation of simple molecules, ab initio simulation of solid-state materials on quantum computers is still in its early stage, mostly owing to the fact that the system size quickly becomes prohibitively large when approaching the thermodynamic limit. In this work, we introduce an orbital-based multifragment approach on top of the periodic density matrix embedding theory, resulting in a significantly smaller problem size for the current near-term quantum computer. We demonstrate the accuracy and efficiency of our method compared with the conventional methodologies and experiments on solid-state systems with complex electronic structures. These include spin-polarized states of a hydrogen chain (1D-H), the equation of state of a boron nitride layer (h-BN) as well as the magnetic ordering in nickel oxide (NiO), a prototypical strongly correlated solid. Our results suggest that quantum embedding combined with a chemically intuitive fragmentation can greatly advance quantum simulation of realistic materials, thereby paving the way for solving important yet classically hard industrial problems on near-term quantum devices.</jats:p>

  • 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
    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
    Grell G, Guo Z, Driver T, Decleva P, Plésiat E, Picón A, González-Vázquez J, Walter P, Marangos JP, Cryan JP, Marinelli A, Palacios A, Martín 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, ISSN: 2643-1564

    X-ray free-electron lasers (XFELs) are now able to provide tunable pairs of intense sub-fs pulses in the soft x-ray regime, paving the way for time-resolved investigations of attosecond charge migration in molecules. However, the stochastic shot-to-shot variation of the XFEL pulses may degrade and eventually hide the observable features. We show by means of state-of-the-art calculations that the damping of the charge migration induced by 260 eV pulses in p-aminophenol due to the shot-to-shot variation of pulses generated at the Linac Coherent Light Source is negligible in comparison to the natural damping due to the intrinsic fluctuation of the initial molecular geometry. This result gives us confidence in the utility of XFEL sub-fs pulses for the measurement of charge migration and other ultrafast charge dynamics.

  • Journal article
    Coste N, Gundin M, Fioretto DA, Thomas SE, Millet C, Mehdi E, Somaschi N, Morassi M, Pont M, Lemaître 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

    Spins in semiconductor quantum dots (QDs) are promising local quantum memories to generate polarization-encoded photonic cluster states, as proposed in the pioneering Lindner and Rudolph scheme (2009 Phys. Rev. Lett. 103 113602). However, harnessing the polarization degree of freedom of the optical transitions is hindered by resonant excitation schemes that are widely used to obtain high photon indistinguishability. Here we show that acoustic phonon-assisted excitation, a scheme that preserves high indistinguishability, also allows to fully exploit the polarization selective optical transitions to initialise and measure single spin states. We access the coherence of hole spin systems in a low transverse magnetic field and directly monitor the spin Larmor precession both during the radiative emission process of an excited state or in the QD ground state. We report a spin state detection fidelity of 94.7±0.2% granted by the optical selection rules and a 25±5 ns hole spin coherence time, demonstrating the potential of this scheme and system to generate linear cluster states with a dozen of photons.

  • Journal article
    Cheng C, Frasinski LJ, Moğol G, Allum F, Howard AJ, Rolles D, Bucksbaum PH, Brouard M, Forbes R, Weinacht Tet al., 2023,

    Multiparticle Cumulant Mapping for Coulomb Explosion Imaging.

    , Phys Rev Lett, Vol: 130

    We extend covariance velocity map ion imaging to four particles, establishing cumulant mapping and allowing for measurements that provide insights usually associated with coincidence detection, but at much higher count rates. Without correction, a fourfold covariance analysis is contaminated by the pairwise correlations of uncorrelated events, but we have addressed this with the calculation of a full cumulant, which subtracts pairwise correlations. We demonstrate the approach on the four-body breakup of formaldehyde following strong field multiple ionization in few-cycle laser pulses. We compare Coulomb explosion imaging for two different pulse durations (30 and 6 fs), highlighting the dynamics that can take place on ultrafast timescales. These results have important implications for Coulomb explosion imaging as a tool for studying ultrafast structural changes in molecules, a capability that is especially desirable for high-count-rate x-ray free-electron laser experiments.

  • 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

    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
    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, Mosca Toba J, Corfield O, Porter G, Thompson RCet al., 2023,

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

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

    Measurement-based cooling is a method by which a quantum system, initially in a thermal state, can be prepared probabilistically in its ground state through some sort of measurement. This is done by making a measurement that heralds the system being in the desired state. Here we demonstrate the application of a measurement-based cooling technique to a trapped atomic ion. The ion is precooled by Doppler laser cooling to a thermal state with a mean excitation of n¯≈18 and the measurement-based cooling technique selects those occasions when the ion happens to be in the motional ground state. The fidelity of the heralding process is greater than 95%. This technique could be applied to other systems that are not as amenable to laser cooling as trapped ions.

  • 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
    Zhang Z-J, Sun J, Yuan X, Yung M-Het al., 2023,

    Low-Depth Hamiltonian Simulation by an Adaptive Product Formula

    , Physical Review Letters, Vol: 130, ISSN: 0031-9007
  • Journal article
    Wu B, Sun J, Huang Q, Yuan Xet al., 2023,

    Overlapped grouping measurement: A unified framework for measuring quantum states

    , Quantum, Vol: 7, Pages: 896-896

    <jats:p>Quantum algorithms designed for realistic quantum many-body systems, such as chemistry and materials, usually require a large number of measurements of the Hamiltonian. Exploiting different ideas, such as importance sampling, observable compatibility, or classical shadows of quantum states, different advanced measurement schemes have been proposed to greatly reduce the large measurement cost. Yet, the underline cost reduction mechanisms seem distinct from each other, and how to systematically find the optimal scheme remains a critical challenge. Here, we address this challenge by proposing a unified framework of quantum measurements, incorporating advanced measurement methods as special cases. Our framework allows us to introduce a general scheme – overlapped grouping measurement, which simultaneously exploits the advantages of most existing methods. An intuitive understanding of the scheme is to partition the measurements into overlapped groups with each one consisting of compatible measurements. We provide explicit grouping strategies and numerically verify its performance for different molecular Hamiltonians with up to 16 qubits. Our numerical result shows significant improvements over existing schemes. Our work paves the way for efficient quantum measurement and fast quantum processing with current and near-term quantum devices.</jats:p>

  • 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.

  • 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
    Latacz BM, Arndt BP, Bauer BB, Devlin JA, Erlewein SR, Fleck M, Jäger 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.

    , Eur Phys J D At Mol Opt Phys, Vol: 77

    ABSTRACT: The BASE collaboration at the antiproton decelerator/ELENA facility of CERN compares the fundamental properties of protons and antiprotons with ultra-high precision. Using advanced Penning trap systems, we have measured the proton and antiproton magnetic moments with fractional uncertainties of 300 parts in a trillion (p.p.t.) and 1.5 parts in a billion (p.p.b.), respectively. The combined measurements improve the resolution of the previous best test in that sector by more than a factor of 3000. Very recently, we have compared the antiproton/proton charge-to-mass ratios with a fractional precision of 16 p.p.t., which improved the previous best measurement by a factor of 4.3. These results allowed us also to perform a differential matter/antimatter clock comparison test to limits better than 3%. Our measurements enable us to set limits on 22 coefficients of CPT- and Lorentz-violating standard model extensions (SME) and to search for potentially asymmetric interactions between antimatter and dark matter. In this article, we review some of the recent achievements and outline recent progress towards a planned improved measurement of the antiproton magnetic moment with an at least tenfold improved fractional accuracy.

  • Journal article
    Hanks M, Kim MS, 2022,

    Fault tolerance in qudit circuit design

    , PHYSICAL REVIEW A, Vol: 106, ISSN: 2469-9926
  • Journal article
    Liu J, Li Z, Zheng H, Yuan X, Sun Jet al., 2022,

    Towards a variational Jordan–Lee–Preskill quantum algorithm

    , Machine Learning: Science and Technology, Vol: 3, Pages: 045030-045030

    <jats:title>Abstract</jats:title> <jats:p>Rapid developments of quantum information technology show promising opportunities for simulating quantum field theory in near-term quantum devices. In this work, we formulate the theory of (time-dependent) variational quantum simulation of the <jats:inline-formula> <jats:tex-math><?CDATA $1+1$?></jats:tex-math> <mml:math xmlns:mml="" overflow="scroll"> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mn>1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="" xlink:href="mlstaca06bieqn1.gif" xlink:type="simple" /> </jats:inline-formula> dimensional <jats:inline-formula> <jats:tex-math><?CDATA $\lambda \phi^4$?></jats:tex-math> <mml:math xmlns:mml="" overflow="scroll"> <mml:mi>λ</mml:mi> <mml:msup> <mml:mi>ϕ</mml:mi> <mml:mn>4</mml:mn> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="" xlink:href="mlstaca06bieqn2.gif" xlink:type="simple" /> </jats:inline-formula> quantum field theory including encoding, state preparation, and time evolution, with several numerical simulation results. These algorithms could be understood as near-term variational quantum circuit (quantum neural network) analogs of the Jordan&nda

  • 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

  • Journal article
    Bellini M, Kwon H, Biagi N, Francesconi S, Zavatta A, Kim MSet al., 2022,

    Demonstrating quantum microscopic reversibility using coherent states of light

    , Physical Review Letters, Vol: 129, Pages: 1-6, ISSN: 0031-9007

    The principle of microscopic reversibility lies at the core of fluctuation theorems, which have extended our understanding of the second law of thermodynamics to the statistical level. In the quantum regime, however, this elementary principle should be amended as the system energy cannot be sharply determined at a given quantum phase space point. In this Letter, we propose and experimentally test a quantum generalization of the microscopic reversibility when a quantum system interacts with a heat bath through energy-preserving unitary dynamics. Quantum effects can be identified by noting that the backward process is less likely to happen in the existence of quantum coherence between the system’s energy eigenstates. The experimental demonstration has been realized by mixing coherent and thermal states in a beam splitter, followed by heterodyne detection in an optical setup. We verify that the quantum modification for the principle of microscopic reversibility is critical in the low-temperature limit, while the quantum-to-classical transition is observed as the temperature of the thermal field gets higher.

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