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Journal articleHoenig D, Thielemann F, Karpa L, et al., 2024,
Trapping Ion Coulomb Crystals in an Optical Lattice
, PHYSICAL REVIEW LETTERS, Vol: 132, ISSN: 0031-9007 -
Journal articleAlaa El-Din K, Alexander O, Frasinski L, et al., 2024,
Efficient prediction of attosecond two-colour pulses from an X-ray free-electron laser with machine learning
, Scientific Reports, Vol: 14, ISSN: 2045-2322X-ray free-electron lasers are sources of coherent, high-intensity X-rays with numerous applications in ultra-fast measurements and dynamic structural imaging. Due to the stochastic nature of the self-amplified spontaneous emission process and the difficulty in controlling injection of electrons, output pulses exhibit significant noise and limited temporal coherence. Standard measurement techniques used for characterizing two-coloured X-ray pulses are challenging, as they are either invasive or diagnostically expensive. In this work, we employ machine learning methods such as neural networks and decision trees to predict the central photon energies of pairs of attosecond fundamental and second harmonic pulses using parameters that are easily recorded at the high-repetition rate of a single shot. Using real experimental data, we apply a detailed feature analysis on the input parameters while optimizing the training time of the machine learning methods. Our predictive models are able to make predictions of central photon energy for one of the pulses without measuring the other pulse, thereby leveraging the use of the spectrometer without having to extend its detection window. We anticipate applications in X-ray spectroscopy using XFELs, such as in time-resolved X-ray absorption and photoemission spectroscopy, where improved measurement of input spectra will lead to better experimental outcomes.
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Journal articleGreenaway S, Petiziol F, Zhao H, et al., 2024,
Variational quantum gate optimization at the pulse level
, SciPost Physics, Vol: 16, ISSN: 2542-4653We experimentally investigate the viability of a variational quantum gate optimizationprotocol informed by the underlying physical Hamiltonian of fixed-frequency transmonqubits. Through the successful experimental optimization of two and three qubit quan-tum gates the utility of the scheme for obtaining gates based on static effective Hamilto-nians is demonstrated. The limits of such a strategy are investigated through the opti-mization of a time-dependent, Floquet-engineered gate, however parameter drift is iden-tified as a key limiting factor preventing the implementation of such a scheme which thevariational optimization protocol is unable to overcome.
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Journal articleWang Z, Wang F, Vovrosh J, et al., 2024,
Quantum simulation of hadronic states with Rydberg-dressed atoms
, PHYSICAL REVIEW A, Vol: 109, ISSN: 2469-9926 -
Journal articleYu S, Liu W, Tao S-J, et al., 2024,
A von-Neumann-like photonic processor and its application in studying quantum signature of chaos
, LIGHT-SCIENCE & APPLICATIONS, Vol: 13, ISSN: 2095-5545 -
Journal articleTang H, Shang X-W, Shi Z-Y, et al., 2024,
Simulating photosynthetic energy transport on a photonic network
, npj Quantum Information, Vol: 10, ISSN: 2056-6387Quantum effects in photosynthetic energy transport in nature, especially for the typical Fenna-Matthews-Olson (FMO) complexes, are extensively studied in quantum biology. Such energy transport processes can be investigated as open quantum systems that blend the quantum coherence and environmental noise, and have been experimentally simulated on a few quantum devices. However, the existing experiments always lack a solid quantum simulation for the FMO energy transport due to their constraints to map a variety of issues in actual FMO complexes that have rich biological meanings. Here we successfully map the full coupling profile of the seven-site FMO structure by comprehensive characterisation and precise control of the evanescent coupling of the three-dimensional waveguide array. By applying a stochastic dynamical modulation on each waveguide, we introduce the base site energy and the dephasing term in coloured noise to faithfully simulate the power spectral density of the FMO complexes. We show our photonic model well interprets the phenomena including reorganisation energy, vibrational assistance, exciton transfer and energy localisation. We further experimentally demonstrate the existence of an optimal transport efficiency at certain dephasing strength, providing a window to closely investigate environment-assisted quantum transport.
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Journal articleMartirosyan G, Ho CJ, Etrych J, et al., 2024,
Observation of Subdiffusive Dynamic Scaling in a Driven and Disordered Bose Gas
, PHYSICAL REVIEW LETTERS, Vol: 132, ISSN: 0031-9007- Cite
- Citations: 8
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Journal articleStray B, Ennis O, Hedges S, et al., 2024,
Centralized design and production of the ultra-high vacuum and laser-stabilization systems for the AION ultra-cold strontium laboratories
, AVS Quantum Science, Vol: 6, ISSN: 2639-0213This paper outlines the centralized design and production of the ultra-high-vacuum sidearm and laser-stabilization systems for the AION Ultra-Cold Strontium Laboratories. Commissioning data on the residual gas and steady-state pressures in the sidearm chambers, on magnetic field quality, on laser stabilization, and on the loading rate for the 3D magneto-optical trap are presented. Streamlining the design and production of the sidearm and laser stabilization systems enabled the AION Collaboration to build and equip in parallel five state-of-the-art Ultra-Cold Strontium Laboratories within 24 months by leveraging key expertise in the collaboration. This approach could serve as a model for the development and construction of other cold atom experiments, such as atomic clock experiments and neutral atom quantum computing systems, by establishing dedicated design and production units at national laboratories.
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Journal articleGreenaway S, Smith A, Mintert F, et al., 2024,
Analogue Quantum Simulation with Fixed-Frequency Transmon Qubits
, QUANTUM, Vol: 8, ISSN: 2521-327X -
Journal articlePetiziol F, Wimberger S, Eckardt A, et al., 2024,
Nonperturbative Floquet engineering of the toric-code Hamiltonian and its ground state
, PHYSICAL REVIEW B, Vol: 109, ISSN: 2469-9950 -
Journal articleBressanini G, Kwon H, Kim MS, 2024,
Gaussian boson sampling with click-counting detectors
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 109, ISSN: 1050-2947Gaussian boson sampling constitutes a prime candidate for an experimental demonstration of quantum advantage within reach with current technological capabilities. The original proposal employs photon-number-resolving detectors, however, these are not widely available. Nevertheless, inexpensive threshold detectors can be combined into a single click-counting detector to achieve approximate photon-number resolution. We investigate the problem of sampling from a general multimode Gaussian state using click-counting detectors and show that the probability of obtaining a given outcome is related to a matrix function which is dubbed as the Kensingtonian. We show how the Kensingtonian relates to the Torontonian and the Hafnian, thus bridging the gap between known Gaussian boson sampling variants. We then prove that, under standard complexity-theoretical conjectures, the model cannot be simulated efficiently.
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Journal articleFekete J, Joshi P, Barrett TJ, et al., 2024,
Quantum Gas-Enabled Direct Mapping of Active Current Density in Percolating Networks of Nanowires
, NANO LETTERS, Vol: 24, Pages: 1309-1315, ISSN: 1530-6984 -
Conference paperVanner MR, 2024,
Brillouin Optomechanics: Strong coupling, the lasing transition, and single-phonon-level operations
, ISSN: 0277-786XBackward Brillouin scattering in whispering-gallery-mode micro-resonators offers an exciting avenue to pursue both classical and quantum optomechanics applications. Our team—the Quantum Measurement Lab—together with our collaborators, are currently exploring and utilizing the favourable properties this platform affords for non-Gaussian motional state preparation of acoustic fields. In particular, the high acoustic frequencies, acoustic mode selectivity, and low optical absorption provide a promising route to overcome current hindrances within optomechanics. Some of our key recent results in this direction include: the observation of Brillouin optomechanical strong coupling, single-phonon addition and subtraction to a thermal state of the acoustic field, advancing the state-of-the-art of mechanical state tomography to observe the non-Gaussian states generated by single- and multi-phonon subtraction, studying the second-order coherence across the Brillouin lasing threshold, and enhancing sideband cooling via zero-photon detection. This talk will cover these results, what they enable, and the broader direction of our lab.
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Conference paperLi Z, Kendall MJH, Zhu R, et al., 2024,
High-Rate Photon-Number Resolved Detection with Transition-Edge Sensors Enabled by Machine Learning
We report a machine-learning-based algorithm that allows transition-edge sensors to distinguish photon number traces at a repetition rate that overcomes their slow recovery time. Detector tomography is performed to benchmark the algorithm’s performance.
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Conference paperLi Z, Kendall MJH, Zhu R, et al., 2024,
High-Rate Photon-Number Resolved Detection with Transition-Edge Sensors Enabled by Machine Learning
We report a machine-learning-based algorithm that allows transition-edge sensors to distinguish photon number traces at a repetition rate that overcomes their slow recovery time. Detector tomography is performed to benchmark the algorithm’s performance.
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Journal articleGarratt D, Matthews M, Marangos J, 2024,
Towards ultrafast soft X-ray spectroscopy of organic photovoltaic devices
, Structural Dynamics, Vol: 11, ISSN: 2329-7778Novel ultrafast x-ray sources based on high harmonic generation and at x-ray free electron lasers are opening up new opportunities to resolve complex ultrafast processes in condensed phase systems with exceptional temporal resolution and atomic site specificity. In this perspective, we present techniques for resolving charge localization, transfer, and separation processes in organic semiconductors and organic photovoltaic devices with time-resolved soft x-ray spectroscopy. We review recent results in ultrafast soft x-ray spectroscopy of these systems and discuss routes to overcome the technical challenges in performing time-resolved x-ray experiments on photosensitive materials with poor thermal conductivity and low pump intensity thresholds for nonlinear effects.
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Journal articleRöser D, Padilla-Castillo JE, Ohayon B, et al., 2024,
Hyperfine structure and isotope shifts of the (4s2) 1S0 →(4s4p) 1P1 transition in atomic zinc
, Physical Review A, Vol: 109, ISSN: 2469-9926We report absolute frequency, isotope shift, radiative lifetime, and hyperfine structure measurements of the (4s2)S01→(4s4p)P11 (213.8 nm) transition in Zn I using a cryogenic buffer gas beam. Laser-induced fluorescence is collected with two orthogonally oriented detectors to take advantage of differences in the emission pattern of the isotopes. This enables a clear distinction between isotopes whose resonances are otherwise unresolved, and a measurement of the Zn67 hyperfine structure parameters, A(Zn67)=20(2)MHz and B(Zn67)=10(5)MHz. We reference our frequency measurements to an ultralow expansion cavity and achieve an uncertainty at the level of 1 MHz, about 1 percent of the natural linewidth of the transition.
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Journal articleGosling JMH, Pontin A, Iacoponi JH, et al., 2024,
Sensing directional noise baths in levitated optomechanics
, Physical Review Research, Vol: 6, ISSN: 2643-1564Optomechanical devices are being harnessed as sensors of ultraweak forces for applications ranging from inertial sensing to the search for the elusive dark matter. For the latter, there is a focus on detection of either higher energy single recoils or ultralight, narrow-band sources; a directional signal is expected. However, the possibility of searching for a stochastic stream of weak impulses, or more generally a directional broadband signal, need not be excluded; with this and other applications in mind, we apply Gaussian white noise impulses with a well defined direction Ψ to a levitated nanosphere trapped and 3D cooled in an optical tweezer. We find that cross-correlation power spectra offer a calibration-free distinctive signature of the presence of a directional broadband force and its orientation quadrant, unlike normal power spectral densities (PSDs). We obtain excellent agreement between theoretical and experimental results. With calibration we are able to measure the angle Ψ, akin to a force compass in a plane. We discuss prospects for extending this technique into the quantum regime and compare the expected behavior of quantum baths and classical baths.
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Conference paperKowalczyk KM, Allegre H, Broughton J, et al., 2024,
Solid High Harmonic Enhancement Near the Band Gap Edge
We present a SWIR wavelength dependence study of high harmonics from MgO and a-Al<inf>2</inf>O<inf>3</inf>. We report robust enhancement for harmonic energies corresponding to the widest bandgap accompanied by gradual changes to the harmonic anisotropy.
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Journal articleBressanini G, Kwon H, Kim MS, 2024,
Gaussian boson sampling at finite temperature
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 109, ISSN: 1050-2947Gaussian boson sampling (GBS) is a promising candidate for an experimental demonstration of quantum advantage using photons. However, sufficiently large noise might hinder a GBS implementation from entering the regime where quantum speedup is achievable. Here, we investigate how thermal noise affects the classical intractability of generic quantum optical sampling experiments, GBS being a particular instance of the latter. We do so by establishing sufficient conditions for an efficient simulation to be feasible, expressed in the form of inequalities between the relevant parameters that characterize the system and its imperfections. We demonstrate that the addition of thermal noise—modeled by (passive) linear optical interaction between the system and a Markovian thermal bath—has the effect of tightening the constraints on the remaining noise parameters, required to show quantum advantage. Furthermore, we show that there exists a threshold temperature, under the assumption of a uniform loss rate, at which quantum sampling experiments become classically simulable, and provide an intuitive physical interpretation by relating this occurrence with the disappearance of the quantum state's nonclassical properties.
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Journal articleJun Park J, Baek K, Kim MS, et al., 2024,
T-depth-optimized quantum search with quantum data-access machine
, Quantum Science and Technology, Vol: 9, ISSN: 2058-9565Quantum search algorithms offer a remarkable advantage of quadraticreduction in query complexity using quantum superposition principle. However, howan actual architecture may access and handle the database in a quantum superposedstate has been largely unexplored so far; the quantum state of data was simply assumedto be prepared and accessed by a black-box operation—so-called oracle, even thoughthis process, if not appropriately designed, may adversely diminish the quantum queryadvantage. Here, we introduce an efficient quantum data-access process, dubbedas quantum data-access machine (QDAM), and present a general architecture forquantum search algorithm. We analyze the runtime of our algorithm in view of thefault-tolerant quantum computation (FTQC) consisting of logical qubits within aneffective quantum error correction code. Specifically, we introduce a measure involvingtwo computational complexities, i.e. quantum query and T-depth complexities, whichcan be critical to assess performance since the logical non-Clifford gates, such as theT (i.e., π/8 rotation) gate, are known to be costliest to implement in FTQC. Ouranalysis shows that for N searching data, a QDAM model exhibiting a logarithmic,i.e., O(log N), growth of the T-depth complexity can be constructed. Further analysisreveals that our QDAM-embedded quantum search requires O(√N × log N) runtimecost. Our study thus demonstrates that the quantum data search algorithm can trulyspeed up over classical approaches with the logarithmic T-depth QDAM as a keycomponent.
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Journal articleMa Y, Kim MS, 2024,
Limitations of probabilistic error cancellation for open dynamics beyond sampling overhead
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 109, ISSN: 1050-2947Quantum simulation of dynamics is an important goal in the noisy intermediate-scale quantum era, within which quantum error mitigation may be a viable path towards modifying or eliminating the effects of noise. Most studies on quantum error mitigation have focused on the resource cost due to its exponential scaling in the circuit depth. Methods such as probabilistic error cancellation rely on discretizing the evolution into finite time steps and applying the mitigation layer after each time step, modifying only the noise part without any Hamiltonian dependence. This may lead to Trotter-like errors in the simulation results even if the error mitigation is implemented ideally, which means that the number of samples is taken as infinite. Here we analyze the aforementioned errors which have been largely neglected before. We show that they are determined by the commutating relations between the superoperators of the unitary part, the device noise part, and the noise part of the open dynamics to be simulated. We include both digital quantum simulation and analog quantum simulation setups and consider defining the ideal error mitigation map both by exactly inverting the noise channel and by approximating it to first order in the time step. We use single-qubit toy models to numerically demonstrate our findings. Our results illustrate fundamental limitations of applying probabilistic error cancellation in a stepwise manner to continuous dynamics, thus motivating the investigations of truly time-continuous error cancellation methods.
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Journal articlePetiziol F, Mintert F, Wimberger S, 2024,
Quantum control by effective counterdiabatic driving
, EPL, Vol: 145, ISSN: 0295-5075 -
Conference paperAllegre H, Broughton J, Klee T, et al., 2024,
Influence of pulse duration on high harmonics emitted from wide bandgap dielectrics
, Conference on Advances in Ultrafast Condensed Phase Physics IV, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X -
Journal articleWiesinger M, Stuhlmann F, Bohman M, et al., 2023,
Trap-integrated fluorescence detection with silicon photomultipliers for sympathetic laser cooling in a cryogenic Penning trap
, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 94, ISSN: 0034-6748 -
Journal articleAhyoune S, Álvarez Melcón A, Arguedas Cuendis S, et 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: 0003-3804In 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.
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Journal articleZuo Z, Hanks M, Kim MS, 2023,
Coherent control of the causal order of entanglement distillation
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 108, ISSN: 1050-2947Indefinite causal order is an evolving field with potential involvement in quantum technologies. Here we propose and study one possible scenario of practical application in quantum communication: a compound entanglement distillation protocol that features two steps of a basic distillation protocol applied in a coherent superposition of two causal orders. This is achieved by using one faulty entangled pair to control-swap two others before a fourth pair is combined with the two swapped ones consecutively. As a result, the protocol distills the four faulty entangled states into one of a higher fidelity. Our protocol has a higher fidelity of distillation and probability of success for some input faulty pairs than conventional concatenations of the basic protocol that follow a definite distillation order. Our proposal shows the advantage of indefinite causal order in an application setting consistent with the requirements of quantum communication.
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Journal articleHo C, Wright S, Sauer B, et al., 2023,
Systematic errors arising from polarization imperfections in measurements of the electron’s electric dipole moment
, Physical Review Research, Vol: 5, ISSN: 2643-1564The 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.
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Journal articleRudolph 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: 2041-1723In 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.
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Journal articleCryer-Jenkins EA, Enzian G, Freisem L, et al., 2023,
Second-order coherence across the Brillouin lasing threshold
, Optica, Vol: 10, Pages: 1432-1438, ISSN: 2334-2536Brillouin–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.
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