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Journal articleSireesh A, Alhajri A, Kim MS, et al., 2025,
Disentangling quantum autoencoder
, Quantum Science and Technology, Vol: 10, ISSN: 2058-9565Entangled quantum states are highly sensitive to noise, which makes it difficult to transfer them over noisy quantum channels or to store them in quantum memory. Here, we propose the disentangling quantum autoencoder (DQAE) to encode entangled states into single-qubit product states. The DQAE provides an exponential improvement in the number of copies needed to transport entangled states across qubit-loss or leakage channels compared to unencoded states. The DQAE can be trained in an unsupervised manner from entangled quantum data. For general states, we train via variational quantum algorithms based on gradient descent with purity-based cost functions, while stabilizer states can be trained via a Metropolis algorithm. For particular classes of states, the number of training data needed to generalize is surprisingly low: for stabilizer states, DQAE generalizes by learning from a number of training data that scales linearly with the number of qubits, while only 1 training sample is sufficient for states evolved with the transverse-field Ising Hamiltonian. Our work provides practical applications for enhancing near-term quantum computers.
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Journal articleXiong P, Ho KKK, Gosling JMH, et al., 2025,
Optical centrifuge for nanoparticles
, Physical Review Research, Vol: 7<jats:p> We study theoretically the creation of an optical centrifuge for the controlled rotation of levitated nanorotors within an optical tweezer. The optical centrifuge's motion is simulated by rapidly rotating the linear polarization of the tightly focused optical field used to form an optical trap. We show that nanorotors, formed by anisotropic nanoparticles levitated within a trap, can be accelerated to well-defined rotational rates in excess of 100 MHz over durations of hundreds of microseconds. The initial conditions required for stable acceleration, based on optical trap properties and the anisotropic susceptibility of the nanorotor are established and confirmed by numerical simulations. We also present initial experiments that have developed tools for the rapid angular acceleration of the polarization vector of the linearly polarized beam that is required to create the centrifuge. We show that over acceleration durations in the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mn>100</a:mn> <a:mspace width="0.28em"/> <a:mi>μ</a:mi> <a:mi mathvariant="normal">s</a:mi> </a:mrow> </a:math> range, high rotational speeds could be achieved in modest vacuum. </jats:p>
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Journal articleAlwehaibi Y, Mer E, Jimenez Machado G, et al., 2025,
Tractable protocol for detection-loophole-free bell tests over long distances
, Physical Review Research, Vol: 7, ISSN: 2643-1564Certifying genuine nonclassical correlations over long distances is essential for device-independent quantum information. In photonic platforms, however, this remains challenging due to photon loss, which opens the detection loophole, rendering violations increasingly difficult for less-efficient detectors. Eberhard showed that using nonmaximally entangled states lowers the detection-efficiency threshold to 66.7%, but existing photonic approaches are restricted to short distances with linear transmittance scaling. Conversely, single-photon event-ready schemes extend the distance with favorable square-root scaling with channel transmittance, yet still demand detection efficiencies above 82.6%. Here, we propose the first all-photonic, heralded entanglement distribution protocol that unifies these two advances: It achieves a postselection-free violation at the Eberhard limit while preserving twin-field-like scaling. We identify the loss independent of the vacuum component amplitude of the prepared state as the source of this enhancement. Our approach addresses both resilience to loss and scalability, providing a practical route toward long-distance, loophole-free Bell tests and device-independent applications with current technology.
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Journal articleDewes BT, Klee T, Cottam ND, et al., 2025,
Fast ultraviolet-C photonics: generating and sensing laser pulses on femtosecond timescales
, LIGHT-SCIENCE & APPLICATIONS, Vol: 14, ISSN: 2095-5545 -
Journal articleKlee T, Broughton JJ, Tisch JWG, 2025,
Efficient generation of femtosecond deep-ultraviolet pulses by single-focus cascaded second-harmonic conversion
, Optics Express, Vol: 33, Pages: 47840-47848We demonstrate an ultrafast deep-ultraviolet source based on single-focus fourth-harmonic (FH) generation of a 1008 kHz Yb laser (1026 nm, 215 fs, 100 nJ-level) using two stages of second harmonic generation. Two critically phase-matched crystals, BiBO for the first stage (1026 nm to 512 nm) and BBO for the second stage (512 nm to 256 nm), are placed within the Rayleigh range of a single focusing lens, yielding a compact, low-loss geometry. We achieve 20.8 ± 0.8% conversion from the fundamental to the FH at 256 nm, with a FH pulse duration of 246 fs measured by cross-correlation. The FH beam profile is smooth and near-circular with M<inf>x</inf><sup>2</sup> = 1.69 ± 0.07, M<inf>y</inf><sup>2</sup> = 1.03 ± 0.05. After thermalization and a small crystal-angle adjustment, the FH pulse energy stability is 0.7% relative standard deviation. By solving the unidirectional pulse propagation equation the experimental data is reproduced with remaining discrepancies attributable to the assumption that the input pulse is transform limited and uncertainties in nonlinear crystal data. To our knowledge, this represents the highest FH conversion efficiency for this type of fundamental laser and establishes the single-focus geometry as a robust route to deep-ultraviolet output for high-repetition-rate, low-pulse-energy laser systems.
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Journal articleMartirosyan G, Gazo M, Etrych J, et al., 2025,
A universal speed limit for spreading of coherence
, NATURE, ISSN: 0028-0836 -
Journal articleGwak G, Roh C, Yoon Y-D, et al., 2025,
Completely characterizing multimode second-order nonlinear optical quantum processes
, Nature Photonics, ISSN: 1749-4885Complete characterization of a multimode optical process has paved the way for understanding complex optical phenomena, leading to the development of novel optical technologies. Until now, however, characterizations have mainly focused on linear optical processes, despite the importance of nonlinear optical processes for photonic technologies. Here we report the complete experimental characterization of multimode second-order nonlinear optical quantum processes—also known as bosonic Gaussian channels. Our resource-efficient characterization method, demonstrated on a 16-mode quantum process, captures the full information of non-unitary quantum evolution and satisfies the required physical condition. This complete characterization enables the identification of eigenquadratures and their associated amplification and noise properties. Moreover, we demonstrate the broad applicability of our method by characterizing various nonlinear optical quantum processes, including cluster-state generation, mode-dependent loss with nonlinear interaction and a quantum noise channel. Our method, by providing a versatile and efficient technique for characterizing a nonlinear optical process, will be beneficial for developing scalable photonic technologies.
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Journal articleAthanasakis M, Peng G, Li S, et al., 2025,
Slowing YbF molecules using radiation pressure
, Physical Review Research, ISSN: 2643-1564We report radiation pressure slowing of YbF molecules to low velocity. In YbF, laser slowing is hindered by leaks out of the optical cycle attributed to low-lying metastable electronic states arising from inner-shell excitation. We bring this population back into the optical cycle once it hasdecayed to the electronic ground state using microwaves to couple the relevant rotational levels. We measure the scattering rate and closure of the optical cycle as repumps are added, and study the destabilzation of dark states by a magnetic field and by polarization modulation, finding thatboth are helpful for maximizing the scattering rate. Starting from a beam with a mean speed of 80 m/s, and using frequency broadened slowing light, we reduce the mean speed of the beam and produce a substantial flux in the low velocity tail of the distribution. Slowing increases the fraction of molecules below 40 m/s from 0.4(1)% to 7.0(2)%, and the fraction below 30 m/s from zero to 3.2(1)%. The establishment of a nearly-closed optical cycle and the production of molecules at low velocity are important steps towards trapping YbF molecules for future measurements of the electron’s electric dipole moment.
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Journal articleCrescimanna V, Yu S, Heshami K, et al., 2025,
Adaptive non-Gaussian quantum state engineering
, Physical Review A, Vol: 112, ISSN: 2469-9926<jats:p>Non-Gaussian quantum states of bosons are a key resource in quantum information science with applications ranging from quantum metrology to fault-tolerant quantum computation. Generation of photonic non-Gaussian resource states, such as Schrödinger's cat and Gottesman-Kitaev-Preskill states, is challenging. In this work, we go beyond existing passive architectures and explore a broad set of adaptive schemes. Our numerical results demonstrate a consistent improvement in the probability of success and fidelity of generating these non-Gaussian quantum states with equivalent resources. We also explore the effect of loss as the primary limiting factor and observe that adaptive schemes lead to more desirable outcomes in terms of overall probability of success and loss tolerance. Our work offers a versatile framework for non-Gaussian resource state generation with the potential to guide future experimental implementations.</jats:p>
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Journal articleCollings FJ, Fitch NJ, Jenkins RA, et al., 2025,
Low-noise environment for probing fundamental symmetries
, NEW JOURNAL OF PHYSICS, Vol: 27, ISSN: 1367-2630 -
Journal articlePadilla-Castillo JE, Hofsass S, Palanki L, et al., 2025,
A Large Magneto-Optical Trap of Cadmium Atoms Loaded From a Cryogenic Buffer Gas Beam
, NATURAL SCIENCES, ISSN: 2698-6248 -
Journal articleCheng MH, Chen Y-C, Wang Q, et al., 2025,
Optimal number-conserved linear encoding for practical fermionic simulation
, PHYSICAL REVIEW RESEARCH, Vol: 7 -
Journal articleMa Y, Hanks M, Gneusheva E, et al., 2025,
Reshaping quantum device noise via repetition code circuits
, Physical Review Research, ISSN: 2643-1564Noise of a quantum processor can be an important resource for simulating open quantum dynamics. However, this requires characterizing the device noise and then transforming it into a target structure. Here we take the first step towards this goal: We analytically and numerically study re-shaping the noise associated with native trapped-ion two-qubit entangling gates via quantum circuits based on repetition codes, and demonstrate our findings on the IonQ Aria-1 quantum hardware. We investigate all the building blocks, including the quantum channels describing noisy two-qubit entangling gates, the compilation of the encoding circuits into native gates, and the propagation of two-qubit errors across ideal single-qubit gates
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Journal articleManceau M, Wall TE, Philip H, et al., 2025,
Demonstration and Frequency Noise Characterization of a 17 μm Quantum Cascade Laser
, LASER & PHOTONICS REVIEWS, ISSN: 1863-8880 -
Journal articlePeng G, Lanigan B, Shah R, et al., 2025,
Large momentum transfer Raman atom interferometer without 𝑘-reversal
, Physical Review Research, Vol: 7, ISSN: 2643-1564We present a Raman atom interferometer using large momentum transfer without reversing thedirection of the effective wavevector (k-reversal). More specifically, we use a microwave π/2 pulseto manipulate the spin state of ⁸⁷Rb atoms before applying a Raman light π pulse to achieve 4ℏk momentum transfer per Raman light pulse. A microwave π pulse in the middle of the interferometer sequence reverses the spin states, which allows closing of the interferometer arms by the same Raman light π pulses without propagation reversal. We present a proof-of-principle demonstration of a 4ℏklarge-momentum-transfer (LMT) atom interferometer and discuss its scalability. Our results extend the scope of using LMT atom optics.
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Journal articleBroughton JJ, Allegre H, Klee T, et al., 2025,
Intensity control of few-cycle laser pulses
, Applied Optics, Vol: 64, Pages: 7060-7064, ISSN: 1559-128XControlling the intensity of few-cycle laser pulses—often with fine and continuous tunability—is essential forapplications ranging from strong-field physics and attosecond science to ultrafast spectroscopy, nonlinear optics, and precision material processing. Yet this remains challenging due to their octave-spanning bandwidth and high sensitivity to dispersion. Conventional polarization-based methods typically rely on ultrabroadband optics, which are complex and costly. We demonstrate a robust and broadly applicable approach that enables precise intensity control while avoiding these demanding optical requirements. Applied to an ∼800 nm laser, the method allows pulse energy tuning over a factor of ∼25 while maintaining a sub-6 fs pulse duration after post compression in an argon-filled hollow fiber and chirped mirror system. Validation through high-harmonic generation in krypton reveals clear intensity-dependent harmonic yields across 30−190 TW/cm². This work provides a practical and effective route to stable, tunable few-cycle pulses for both experimental and applied settings.
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Journal articleLi Y, Broughton JJ, Tisch JWG, 2025,
Temporal compression of Yb-doped laser pulses in cascaded gas-filled hollow fibers
, OPTICS CONTINUUM, Vol: 4, Pages: 1732-1743 -
Journal articleLatacz BM, Erlewein SR, Fleck M, et al., 2025,
Coherent spectroscopy with a single antiproton spin
, Nature, Vol: 644, Pages: 64-68, ISSN: 0028-0836Coherent quantum transition spectroscopy is a powerful tool in metrology¹, quantum information processing², magnetometry³, and precision tests of the Standard Model⁴. It was applied with great success in proton and deuteron magnetic moment measurements⁵, which culminated in MASER spectroscopy with sub-parts per trillion resolution⁶ and many other experiments at the forefront of physics⁷. All these experiments were performed on macroscopic ensembles of particles, while the coherent spectroscopy of a “free” single nuclear spin has never been reported before. Here, we demonstrate coherent quantum transition spectroscopy of the spin of a single antiproton stored in a cryogenic Penning-trap system. We apply a multi-trap technique⁸, detect the antiproton spin-state using the continuous Stern-Gerlach-effect⁹, and transport the particle to the homogeneous magnetic field of a precision trap (PT). Here, we induce the coherent dynamics and analyze the result by quantum-projection measurements in the analysis trap¹⁰ . We observe for the first time Rabi-oscillations of an antiproton spin and achieve in time-series measurements spin inversion probabilities above 80% at spin coherence times of ≈ 50s. Scans of single-particle spin resonances show inversions >70%, at transition line-widths 16 times narrower than in previous measurements⁸, limited by cyclotron frequency measurement decoherence. This achievement marks a major step towards at least 10-fold improved tests of matter/antimatter symmetry using proton and antiproton magnetic moments.
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Journal articleHaug T, Aolita L, Kim MS, 2025,
Probing quantum complexity via universal saturation of stabilizer entropies
, Quantum, Vol: 9, Pages: 1801-1801, ISSN: 2521-327XNonstabilizerness or `magic' is a key resource for quantum computing and a necessary condition for quantum advantage. Non-Clifford operations turn stabilizer states into resourceful states, where the amount of nonstabilizerness is quantified by resource measures such as stabilizer Rényi entropies (SREs). Here, we show that SREs saturate their maximum value at a critical number of non-Clifford operations. Close to the critical point SREs show universal behavior. Remarkably, the derivative of the SRE crosses at the same point independent of the number of qubits and can be rescaled onto a single curve. We find that the critical point depends non-trivially on Rényi index α. For random Clifford circuits doped with T-gates, the critical T-gate density scales independently of α. In contrast, for random Hamiltonian evolution, the critical time scales linearly with qubit number for α>1, while it is a constant for α<1. This highlights that α-SREs reveal fundamentally different aspects of nonstabilizerness depending on α: α-SREs with α<1 relate to Clifford simulation complexity, while α>1 probe the distance to the closest stabilizer state and approximate state certification cost via Pauli measurements. As technical contributions, we observe that the Pauli spectrum of random evolution can be approximated by two highly concentrated peaks which allows us to compute its SRE. Further, we introduce a class of random evolution that can be expressed as random Clifford circuits and rotations, where we provide its exact SRE. Our results opens up new approaches to characterize the complexity of quantum systems.
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Journal articleLi Z, Solomons NR, Bulmer JFF, et al., 2025,
A complexity transition in displaced Gaussian Boson sampling
, npj Quantum Information, Vol: 11, ISSN: 2056-6387Gaussian Boson Sampling (GBS) is the problem of sampling from the output of photon-number-resolving measurements of squeezed states input to a linear optical interferometer. For purposes of demonstrating quantum computational advantage as well as practical applications,a large photon number is often desirable. However, producing squeezed states with high photon numbers is experimentally challenging. In this work, we examine the computational complexity implications of increasing the photon number by introducing coherent states. This displaces the state in phase space and as such we call this modified problem Displaced GBS. By utilising a connection to the matching polynomial in graph theory, we first describe an efficient classical algorithm for Displaced GBS when displacement is high or when the output state is represented by a non-negative graph. Then we provide complexity theoretic arguments for the quantum advantage of the problem in the low-displacement regime and numerically quantify where the complexity transition occurs.
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Journal articleVylegzhanin A, Brown DJ, Kornovan DF, et al., 2025,
Towards a fictitious magnetic field trap for both ground and Rydberg state <SUP>87</SUP>Rb atoms via the evanescent field of an optical nanofiber
, NEW JOURNAL OF PHYSICS, Vol: 27, ISSN: 1367-2630 -
Journal articleBressanini G, Seron B, Novo L, et al., 2025,
Binned-detector probability distributions for Gaussian boson sampling validation
, Physical Review A: Atomic, Molecular and Optical Physics, Vol: 112, ISSN: 1050-2947Gaussian boson sampling (GBS), a computational problem conjectured to be hard to simulate on a classical machine, has been at the forefront of recent years' experimental and theoretical efforts to demonstrate quantum advantage. The classical intractability of the sampling task makes validating these experiments a challenging and essential undertaking. In this paper, we propose binned-detector probability distributions as a suitable quantity to statistically validate GBS experiments employing photon-number-resolving detectors. We develop the theoretical framework to compute such distributions by leveraging their connection with their respective characteristic function. The latter may be efficiently and analytically computed for squeezed input states as well as for relevant classical hypothesis like squashed states. Our theoretical framework encompasses other validation methods based on marginal distributions and correlation functions. Additionally, it can analytically accommodate various sources of noise, such as losses and partial distinguishability, a feature that has received limited attention within the GBS framework so far. We also derive how binned-detector probability distributions behave when Haar averaged over all possible interferometric networks, extending known results for Fock boson sampling.
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Journal articleLi Z, Kendall MJH, Machado GJ, et al., 2025,
Boosting photon-number-resolved detection rates of transition-edge sensors by machine learning
, Optica Quantum, Vol: 3, Pages: 246-246, ISSN: 2837-6714Transition-edge sensors (TESs) are very effective photon-number-resolving (PNR) detectors that have enabled many photonic quantum technologies. However, their relatively slow thermal recovery time severely limits their operation rate in experimental scenarios compared with leading non-PNR detectors. In this work, we develop an algorithmic approach that enables TESs to detect and accurately classify photon pulses without waiting for a full recovery time between detection events. We propose two machine-learning-based signal processing methods: one supervised learning method and one unsupervised clustering method. By benchmarking against data obtained using coherent states and squeezed states, we show that the methods extend the TES operation rate to 800 kHz, achieving at least a four-fold improvement, whilst maintaining accurate photon-number assignment up to at least five photons. Our algorithms will find utility in applications where high rates of PNR detection are required and in technologies that demand fast active feed-forward of PNR detection outcomes.
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Journal articleMaslennikov DR, Maimaris M, Ning H, et al., 2025,
Interplay between Mixed and Pure Exciton States Controls Singlet Fission in Rubrene Single Crystals
, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 147, Pages: 23536-23544, ISSN: 0002-7863 -
Journal articleHo CJ, Fischer SM, Martirosyan G, et al., 2025,
Joule expansion of a quantum gas
, PHYSICAL REVIEW RESEARCH, Vol: 7 -
Journal articleCheng MH, Khosla KE, Self CN, et al., 2025,
Clifford circuit initialization for variational quantum algorithms
, Physical Review A, Vol: 111, ISSN: 2469-9926We present an initialization method for variational quantum algorithms applicable to intermediate-scale quantum computers. The method explores the efficiently classically simulable Clifford points of a parameterized quantum circuit, using simulated annealing to find a low-energy initial state. We provide numerical evidence of the effectiveness of the technique for different choices of the Hamiltonian structure, number of qubits, and circuit depth. While a number of problems are considered, we note that the method is particularly useful for quantum chemistry problems, for which it is able to capture long-range correlation energy. The presented method could help achieve a quantum advantage in noisy or fault-tolerant intermediate-scale devices by preparing a high-quality initial state.
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Journal articleEtrych J, Martirosyan G, Cao A, et al., 2025,
Universal Quantum Dynamics of Bose Polarons
, PHYSICAL REVIEW X, Vol: 15, ISSN: 2160-3308- Cite
- Citations: 6
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Journal articleLeonhardt M, Schweitzer S, Abbass F, et al., 2025,
Proton transport from the antimatter factory of CERN
, Nature, ISSN: 0028-0836Precision measurements using low-energy antiprotons, exclusively available at the antimatter factory (AMF) of CERN1, offer stringent tests of charge–parity–time (CPT) invariance, which is a fundamental symmetry in the Standard Model of particle physics2. These tests have been realized, for example, in antiprotonic helium3 and antihydrogen4. In our cryogenic Penning-trap experiments5, we measure the magnetic moments6,7 and charge-to-mass ratios of protons and antiprotons and now provide the most precise test of CPT invariance in the baryon sector8. Our experiments are limited by magnetic field fluctuations imposed by the decelerators in the AMF; therefore, we are advancing the relocation of antiprotons to dedicated precision laboratories. Here we present the successful transport of a trapped proton cloud from the AMF using BASE-STEP9—a transportable, superconducting, autonomous and open Penning-trap system that can distribute antiprotons into other experiments. We transferred the trapped protons from our experimental area at the AMF onto a truck and transported them across the Meyrin site of CERN, demonstrating autonomous operation without external power for 4 h and loss-free proton relocation. We thereby confirm the feasibility of transferring particles into low-noise laboratories in the vicinity of the AMF and of using a power generator on the truck10 to reach laboratories throughout Europe. This marks the potential start of a new era in precision antimatter research, enabling low-noise measurements of antiprotons, the charged antimatter ions H+11 and H-2 (ref. 12), and other accelerator-produced ions, such as hydrogen-like lead or uranium ions13,14.
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Journal articleLi H, Xie J, Kwon H, et al., 2025,
Experimental demonstration of generalized quantum fluctuation theorems in the presence of coherence
, Science Advances, Vol: 11, ISSN: 2375-2548Fluctuation theorems have elevated the second law of thermodynamics to a statistical realm by establishing a connection between time-forward and time-reversal probabilities, providing invaluable insight into nonequilibrium dynamics. While well established in classical systems, their quantum generalization, incorporating coherence and the diversity of quantum noise, remains open. We report the experimental validation of a quantum fluctuation theorem (QFT) in a photonic system, applicable to general quantum processes with nonclassical characteristics, including quasi-probabilistic descriptions of entropy production and multiple time-reversal processes. Our experiment confirms that the ratio between the quasi-probabilities of the time-forward and any multiple time-reversal processes obeys a generalized Crooks QFT. Moreover, coherence induced by a quantum process leads to the imaginary components of quantum entropy production, governing the phase factor in the QFT. These findings underscore the fundamental symmetry between a general quantum process and its time reversal, providing an elementary toolkit to explore noisy quantum information processing.
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Journal articleAlexander O, Ayuso D, Matthews M, et al., 2025,
Attosecond physics and technology
, APPLIED PHYSICS LETTERS, Vol: 126, ISSN: 0003-6951- Cite
- Citations: 1
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