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  • Journal article
    Wiesinger M, Stuhlmann F, Bohman M, Micke P, Will C, Yildiz H, Abbass F, Arndt BP, Devlin JA, Erlewein S, Fleck M, Jaeger JI, Latacz BM, Schweitzer D, Umbrazunas G, Wursten E, Blaum K, Matsuda Y, Mooser A, Quint W, Soter A, Walz J, Smorra C, Ulmer Set al., 2023,

    Trap-integrated fluorescence detection with silicon photomultipliers for sympathetic laser cooling in a cryogenic Penning trap

  • Journal article
    Ho C, Wright S, Sauer B, Tarbutt Met al., 2023,

    Systematic errors arising from polarization imperfections in measurements of the electron’s electric dipole moment

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

    The electron’s electric dipole moment (eEDM) can be determined by polarizing the spin of an atom or a molecule and then measuring the spin precession frequency in an applied electric field. Radiation is used to polarize the spin and then analyze the precession angle, and the measurement is often sensitive to the polarization of this radiation. We show how systematic errors can arise when both the polarization of the radiation and the magnitude of the electric field are imperfectly controlled. We derive approximate analytical expressions for these errors, confirm their accuracy numerically, and show how they can be corrected empirically. We consider spin manipulation using single-photon pulses, Raman pulses, and Stimulated Raman Adiabatic Passage (STIRAP), and show that STIRAP provides better immunity to these systematic errors. An experimental study of these errors partly supports our findings but also reveals another potential error that is not captured by this analysis.

  • Journal article
    Ahyoune S, Álvarez Melcón A, Arguedas Cuendis S, Calatroni S, Cogollos C, Devlin J, DíazMorcillo A, DíezIbáñez D, Döbrich B, Galindo J, Gallego JD, GarcíaBarceló JM, Gimeno B, Golm J, Gu Y, Herwig L, Garcia Irastorza I, LozanoGuerrero AJ, Malbrunot C, MiraldaEscudé J, MonzóCabrera J, Navarro P, NavarroMadrid JR, Redondo J, ReinaValero J, Schmieden K, Schneemann T, Siodlaczek M, Ulmer S, Wuensch Wet al., 2023,

    A proposal for a low-frequency axion search in the 1–2 μ eV range and below with the babyIAXO magnet

    , Annalen der Physik, Vol: 535, ISSN: 0003-3804

    In the near future BabyIAXO will be the most powerful axion helioscope,relying on a custom-made magnet of two bores of 70 cm diameter and 10 mlong, with a total available magnetic volume of more than 7 m3. In thisdocument, it proposes and describe the implementation of low-frequencyaxion haloscope setups suitable for operation inside the BabyIAXO magnet.The RADES proposal has a potential sensitivity to the axion-photon couplingga𝜸 down to values corresponding to the KSVZ model, in the (currentlyunexplored) mass range between 1 and 2 𝛍 eV, after a total effective exposureof 440 days. This mass range is covered by the use of four differentlydimensioned 5-meter-long cavities, equipped with a tuning mechanism basedon inner turning plates. A setup like the one proposed will also allow anexploration of the same mass range for hidden photons coupled to photons.An additional complementary apparatus is proposed using LC circuits andexploring the low energy range (≈ 10−4 − 10−1 𝛍 eV). The setup includes acryostat and cooling system to cool down the BabyIAXO bore down to about 5K, as well as an appropriate low-noise signal amplification anddetection chain.

  • Journal article
    Rudolph T, Virmani SS, 2023,

    The two-qubit singlet/triplet measurement is universal for quantum computing given only maximally-mixed initial states

    , Nature Communications, Vol: 14, ISSN: 2041-1723

    In order to delineate which minimalistic physical primitives can enable the full power of universal quantum computing, it has been fruitful to consider various measurement based architectures which reduce or eliminate the use of coherent unitary evolution, and also involve operations that are physically natural. In this context previous works had shown that the triplet-singlet measurement of two qubit angular momentum (or equivalently two qubit exchange symmetry) yields the power of quantum computation given access to a few additional different single qubit states or gates. However, Freedman, Hastings and Shokrian-Zini1 recently proposed a remarkable conjecture, called the ‘STP=BQP’ conjecture, which states that the two-qubit singlet/triplet measurement is quantum computationally universal given only an initial ensemble of maximally mixed single qubits. In this work we prove this conjecture. This provides a method for quantum computing that is fully rotationally symmetric (i.e. reference frame independent), using primitives that are physically very-accessible, naturally resilient to certain forms of error, and provably the simplest possible.

  • Journal article
    Cryer-Jenkins EA, Enzian G, Freisem L, Moroney N, Price JJ, Svela AO, Major KD, Vanner MRet al., 2023,

    Second-order coherence across the Brillouin lasing threshold

    , Optica, Vol: 10, Pages: 1432-1438, ISSN: 2334-2536

    Brillouin–Mandelstam scattering is one of the most accessible nonlinear optical phenomena and has been widely studied since its theoretical discovery one hundred years ago. The scattering mechanism is a three-wave-mixing process between two optical fields and one acoustic field and has found a broad range of applications spanning microscopy to ultra-narrow-linewidth lasers. Building on the success of utilizing this nonlinearity at a classical level, a rich avenue is now being opened to explore Brillouin scattering within the paradigm of quantum optics. Here, we take a key step in this direction by employing quantum optical techniques yet to be utilized for Brillouin scattering to characterize the second-order coherence of Stokes scattering across the Brillouin lasing threshold. We use a silica microsphere resonator and single-photon counters to observe the expected transition from bunched statistics of thermal light below the lasing threshold to Poissonian statistics of coherent light above the threshold. Notably, at powers approaching the lasing threshold, we also observe super-thermal statistics, which arise due to instability and a “flickering” in and out of lasing as the pump field is transiently depleted. The statistics observed across the transition, including the “flickering,” are a result of the full nonlinear three-wave-mixing process and cannot be captured by a linearized model. These measurements are in good agreement with numerical solutions of the three-wave Langevin equations and are well demarcated by analytical expressions for the instability and the lasing thresholds. These results demonstrate that applying second-order-coherence and photon-counting measurements to Brillouin scattering provides new methods to advance our understanding of Brillouin scattering itself and progress toward quantum-state preparation and characterization of acoustic modes.

  • Journal article
    Ma Y, Hanks M, Kim MS, 2023,

    Non-Pauli errors can be efficiently sampled in qudit surface codes

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

    Surface codes are the most promising candidates for fault-tolerant quantum computation. Single qudit errors are typically modeled as Pauli operators, to which general errors are converted via randomizing methods. In this Letter, we quantify remaining correlations after syndrome measurement for a qudit 2D surface code subject to non-Pauli errors via loops on the lattice, using percolation theory. Below the error correction threshold, remaining correlations are sparse and locally constrained. Syndromes for qudit surface codes are therefore efficiently samplable for non-Pauli errors, independent of the exact forms of the error and decoder.

  • Journal article
    Smorra C, Abbass F, Schweitzer D, Bohman M, Devine JD, Dutheil Y, Hobl A, Arndt B, Bauer BB, Devlin JA, Erlewein S, Fleck M, Jäger JI, Latacz BM, Micke P, Schiffelholz M, Umbrazunas G, Wiesinger M, Will C, Wursten E, Yildiz H, Blaum K, Matsuda Y, Mooser A, Ospelkaus C, Quint W, Soter A, Walz J, Yamazaki Y, Ulmer Set al., 2023,

    BASE-STEP: a transportable antiproton reservoir for fundamental interaction studies

    , Review of Scientific Instruments, Vol: 94, ISSN: 0034-6748

    Currently, the world's only source of low-energy antiprotons is the AD/ELENA facility located at CERN. To date, all precision measurements on single antiprotons have been conducted at this facility and provide stringent tests of fundamental interactions and their symmetries. However, magnetic field fluctuations from the facility operation limit the precision of upcoming measurements. To overcome this limitation, we have designed the transportable antiproton trap system BASE-STEP to relocate antiprotons to laboratories with a calm magnetic environment. We anticipate that the transportable antiproton trap will facilitate enhanced tests of charge, parity, and time-reversal invariance with antiprotons and provide new experimental possibilities of using transported antiprotons and other accelerator-produced exotic ions. We present here the technical design of the transportable trap system. This includes the transportable superconducting magnet, the cryogenic inlay consisting of the trap stack and detection systems, and the differential pumping section to suppress the residual gas flow into the cryogenic trap chamber.

  • 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
    Yu S, Zhong Z-P, Fang Y, Patel RB, Li Q-P, Liu W, Li Z, Xu L, Sagona-Stophel S, Mer E, Thomas SE, Meng Y, Li Z-P, Yang Y-Z, Wang Z-A, Guo N-J, Zhang W-H, Tranmer GK, Dong Y, Wang Y-T, Tang J-S, Li C-F, Walmsley IA, Guo G-Cet al., 2023,

    A universal programmable Gaussian boson sampler for drug discovery

  • Journal article
    Alexander O, Barnard J, Larsen E, Avni T, Jarosch S, Ferchaud C, Gregory A, Parker S, Galinis G, Tofful A, Garratt D, Matthews M, Marangos Jet al., 2023,

    Observation of recollision-based high-harmonic generation in liquid isopropanol and the role of electron scattering

    , Physical Review Research, ISSN: 2643-1564
  • Journal article
    Smith AWR, Paige AJ, Kim MS, 2023,

    Faster variational quantum algorithms with quantum kernel-based surrogate models

    , Quantum Science and Technology, Vol: 8, ISSN: 2058-9565

    We present a new optimization strategy for small-to-intermediate scale variational quantum algorithms (VQAs) on noisy near-term quantum processors which uses a Gaussian process surrogate model equipped with a classically-evaluated quantum kernel. VQAs are typically optimized using gradient-based approaches however these are difficult to implement on current noisy devices, requiring large numbers of objective function evaluations. Our approach shifts this computational burden onto the classical optimizer component of these hybrid algorithms, greatly reducing the number of quantum circuit evaluations required from the quantum processor. We focus on the variational quantum eigensolver (VQE) algorithm and demonstrate numerically that these surrogate models are particularly well suited to the algorithm's objective function. Next, we apply these models to both noiseless and noisy VQE simulations and show that they exhibit better performance than widely-used classical kernels in terms of final accuracy and convergence speed. Compared to the typically-used stochastic gradient-descent approach to VQAs, our quantum kernel-based approach is found to consistently achieve significantly higher accuracy while requiring less than an order of magnitude fewer quantum circuit executions. We analyze the performance of the quantum kernel-based models in terms of the kernels' induced feature spaces and explicitly construct their feature maps. Finally, we describe a scheme for approximating the best-performing quantum kernel using a classically-efficient tensor network representation of its input state and so provide a pathway for scaling this strategy to larger systems.

  • Journal article
    Latacz BM, Arndt BP, Devlin JA, Erlewein SR, Fleck M, Jager JI, Micke P, Umbrazunas G, Wursten E, Abbass F, Schweitzer D, Wiesinger M, Will C, Yildiz H, Blaum K, Matsuda Y, Mooser A, Ospelkaus C, Smorra C, Soter A, Quint W, Walz J, Yamazaki Y, Ulmer Set al., 2023,

    Ultra-thin polymer foil cryogenic window for antiproton deceleration and storage

  • Journal article
    Yu S, Zhong Z-P, Fang Y, Patel RB, Li Q-P, Liu W, Li Z, Xu L, Sagona-Stophel S, Mer E, Thomas SE, Meng Y, Li Z-P, Yang Y-Z, Wang Z-A, Guo N-J, Zhang W-H, Tranmer GK, Dong Y, Wang Y-T, Tang J-S, Li C-F, Walmsley IA, Guo G-Cet al., 2023,

    A universal programmable Gaussian boson sampler for drug discovery.

    , Nat Comput Sci, Vol: 3, Pages: 839-848

    Gaussian boson sampling (GBS) has the potential to solve complex graph problems, such as clique finding, which is relevant to drug discovery tasks. However, realizing the full benefits of quantum enhancements requires large-scale quantum hardware with universal programmability. Here we have developed a time-bin-encoded GBS photonic quantum processor that is universal, programmable and software-scalable. Our processor features freely adjustable squeezing parameters and can implement arbitrary unitary operations with a programmable interferometer. Leveraging our processor, we successfully executed clique finding on a 32-node graph, achieving approximately twice the success probability compared to classical sampling. As proof of concept, we implemented a versatile quantum drug discovery platform using this GBS processor, enabling molecular docking and RNA-folding prediction tasks. Our work achieves GBS circuitry with its universal and programmable architecture, advancing GBS toward use in real-world applications.

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

    Reflective dielectric cavity enhanced emission from hexagonal boron nitride spin defect arrays.

    , Nanoscale, Vol: 15, Pages: 15000-15007

    Among the various kinds of spin defects in hexagonal boron nitride (hBN), the negatively charged boron vacancy (VB-) spin defect that can be site-specifically generated is undoubtedly a potential candidate for quantum sensing, but its low quantum efficiency restricts its practical applications. Here, we demonstrate a robust enhancement structure called reflective dielectric cavity (RDC) with advantages including easy on-chip integration, convenient processing, low cost and suitable broad-spectrum enhancement for VB- defects. In the experiment, we used a metal reflective layer under the hBN flakes, filled with a transition dielectric layer in the middle, and adjusted the thickness of the dielectric layer to achieve the best coupling between RDC and spin defects in hBN. A remarkable 11-fold enhancement in the fluorescence intensity of VB- spin defects in hBN flakes can be achieved. By designing the metal layer into a waveguide structure, high-contrast optically detected magnetic resonance (ODMR) signal (∼21%) can be obtained. The oxide layer of the RDC can be used as the integrated material to implement secondary processing of micro-nano photonic devices, which means that it can be combined with other enhancement structures to achieve stronger enhancement. This work has guiding significance for realizing the on-chip integration of spin defects in two-dimensional materials.

  • 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

  • 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
    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
    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
    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
    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
    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 article
    Ruberti M, Averbukh V, 2023,

    Advances in modeling attosecond electron dynamics in molecular photoionization

  • 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.

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