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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<jats:p>Transition-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.</jats:p>
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Journal articleDevlin J, 2025,
Dark matter: what is it, and can quantum sensors help find it?
, Contemporary Physics, ISSN: 0010-7514Dark matter is the name given to the unknown substance or substances which appears to make up 26.4(6)% of the total mass-energy density of the Universe, makingit 5 times more abundant than normal matter. Over 50 years of measurements havegiven us considerable evidence for the existence of dark matter and some of itsproperties. However, we still do not know, microscopically, what sort of stuff it is.In recent years, researchers have started to use techniques developed in quantumscience to build experiments which are sensitive to certain types of dark matter.These techniques rely on the remarkable progress in isolating and measuring specific quantum systems, to such an extent that these experiments are now sensitiveto the weak perturbations due to dark matter. This article gives an introduction todark matter and efforts to search for it with quantum sensors.
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Journal articleLatacz BM, Erlewein SR, Fleck M, et al., 2025,
Coherent spectroscopy with a single antiproton spin
, Nature, 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 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: 0003-6951In this Perspective, we provide an overview of the field of attosecond physics and technology for which the 2023 Nobel Prize in Physics was awarded to Pierre Agostini, Ferenc Krausz, and Anne L'Huillier. We look at the current state-of-the-art in attosecond timescale measurements and recent advances enabled by the light field driven technology inspired by the earlier work in the field. We end this Perspective with some comments on the exciting future directions now developing in the field.
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Journal articleAthanasakis-Kaklamanakis M, Wilkins SG, Skripnikov LV, et al., 2025,
Electron correlation and relativistic effects in the excited states of radium monofluoride.
, Nat Commun, Vol: 16Highly accurate and precise electronic structure calculations of heavy radioactive atoms and their molecules are important for several research areas, including chemical, nuclear, and particle physics. Ab initio quantum chemistry can elucidate structural details in these systems that emerge from the interplay of relativistic and electron correlation effects, but the large number of electrons complicates the calculations, and the scarcity of experiments prevents insightful theory-experiment comparisons. Here we report the spectroscopy of the 14 lowest excited electronic states in the radioactive molecule radium monofluoride (RaF), which is proposed as a sensitive probe for searches of new physics. The observed excitation energies are compared with state-of-the-art relativistic Fock-space coupled cluster calculations, which achieve an agreement of ≥99.64% (within ~12 meV) with experiment for all states. Guided by theory, a firm assignment of the angular momentum and term symbol is made for 10 states and a tentative assignment for 4 states. The role of high-order electron correlation and quantum electrodynamics effects in the excitation energies is studied and found to be important for all states.
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Journal articleAllegre H, Broughton JJ, Klee T, et al., 2025,
Extension of high-harmonic generation cutoff in solids to 50 eV using MgO.
, Opt Lett, Vol: 50, Pages: 1492-1495High-harmonic generation (HHG) in solids driven by femtosecond lasers is a promising method for the compact production of coherent extreme ultraviolet (XUV) radiation but so far has been limited to photon energies below 40 eV. Here, we report the highest ever recorded photon energy for a harmonic in a solid sample, reaching 50 eV (31st harmonic) in 100-µm-thick MgO, using a 780 nm, 30 fs driving pulse. This is achieved through optimization of the spectrometer and detection efficiency, as well as an increase in emission efficiency enabled by a larger excitation area and the use of a multi-cycle pulse. We observe that the harmonic cutoff exhibits nontrivial behavior as a function of laser field strength, suggesting that an extension to our existing understanding of the generation process may be needed. This work demonstrates further the potential for compact XUV sources beyond 50 eV based on solid-state media.
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Journal articleCryer-Jenkins EA, Major KD, Clarke J, et al., 2025,
Enhanced Laser Cooling of a Mechanical Resonator via Zero-Photon Detection.
, Phys Rev Lett, Vol: 134Throughout quantum science and technology, measurement is used as a powerful resource for nonlinear operations and quantum state engineering. In particular, single-photon detection is commonly employed for quantum-information applications and tests of fundamental physics. By contrast, and perhaps counterintuitively, measurement of the absence of photons also provides useful information, and offers significant potential for a wide range of new experimental directions. Here, we propose and experimentally demonstrate cooling of a mechanical resonator below its laser-cooled mechanical occupation via zero-photon detection on the anti-Stokes scattered optical field and verify this cooling through heterodyne measurements. Our measurements are well captured by a stochastic master equation and the techniques introduced here open new avenues for cooling, quantum thermodynamics, quantum state engineering, and quantum measurement and control.
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Journal articleSun J, Vilchez-Estevez L, Vedral V, et al., 2025,
Probing spectral features of quantum many-body systems with quantum simulators.
, Nat Commun, Vol: 16The efficient probing of spectral features is important for characterising and understanding the structure and dynamics of quantum materials. In this work, we establish a framework for probing the excitation spectrum of quantum many-body systems with quantum simulators. Our approach effectively realises a spectral detector by processing the dynamics of observables with time intervals drawn from a defined probability distribution, which only requires native time evolution governed by the Hamiltonian without ancilla. The critical element of our method is the engineered emergence of frequency resonance such that the excitation spectrum can be probed. We show that the time complexity for transition energy estimation has a logarithmic dependence on simulation accuracy and how such observation can be guaranteed in certain many-body systems. We discuss the noise robustness of our spectroscopic method and show that the total running time maintains polynomial dependence on accuracy in the presence of device noise. We further numerically test the error dependence and the scalability of our method for lattice models. We present simulation results for the spectral features of typical quantum systems, either gapped or gapless, including quantum spins, fermions and bosons. We demonstrate how excitation spectra of spin-lattice models can be probed experimentally with IBM quantum devices.
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Journal articleWang Y, Rodewald J, Lopez O, et al., 2025,
Wavelength modulation laser spectroscopy of N2O at 17 µm
, New Journal of Physics, Vol: 27Using a mid-infrared quantum cascade laser and wavelength modulation absorption spectroscopy, we measure the frequencies of ro-vibrational transitions of N<inf>2</inf>O in the 17 µm region with uncertainties below 5 MHz. These lines, corresponding to the bending mode of the molecule, can be used for calibration of spectrometers in this spectral region. We present a model for the lineshapes of absorption features in wavelength modulation spectroscopy that takes into account Doppler broadening, collisional broadening, saturation of the absorption, and lineshape distortion due to frequency and intensity modulation. Combining our data with previous measurements, we provide a set of spectroscopic parameters for several vibrational states of N<inf>2</inf>O. The lines measured here fall in the same spectral region as a mid-infrared frequency reference that we are currently developing using trapped, ultracold molecules. With such a frequency reference, the spectroscopic methods demonstrated here have the potential to improve frequency calibration in this part of the spectrum.
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Journal articleClarke J, Cryer-Jenkins EA, Gupta A, et al., 2025,
Theoretical framework for enhancing or enabling cooling of a mechanical resonator via the anti-Stokes or Stokes interaction and zero-photon detection
, Physical Review A, Vol: 111, ISSN: 2469-9926We develop a theoretical framework to describe how zero-photon detection may be utilized to enhance optomechanical laser cooling via the anti-Stokes interaction and, somewhat surprisingly, enable cooling via the Stokes interaction commonly associated with heating. Our description includes both pulsed and continuous measurements as well as optical detection efficiency and open-system dynamics. For both cases, we discuss how the cooling depends on the system parameters such as detection efficiency and optomechanical cooperativity, and we study the continuous-measurement-induced dynamics, contrasting with single-photon-detection events. For the Stokes case, we explore the interplay between cooling and heating via optomechanical parametric amplification, and we find the minimum efficiency required to cool a mechanical oscillator via zero-photon detection. This work serves as a companion article to our recent experiment [E. A. Cryer-Jenkins, Phys. Rev. Lett. 134, 073601 (2025)10.1103/PhysRevLett.134.073601], which demonstrated enhanced laser cooling of a mechanical oscillator via zero-photon detection on the anti-Stokes signal. The cooling techniques developed here can be applied to a wide range of areas including nonclassical state preparation, quantum thermodynamics, and avoiding the often unwanted heating effects of parametric amplification.
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Journal articleVanner M, Cryer-Jenkins E, Leung A, et al., 2025,
Brillouin-Mandelstam scattering in telecommunications optical fiber at millikelvin temperatures
, APL Photonics -
Journal articleWang P, Kwon H, Luan C-Y, et al., 2025,
Author Correction: Snapshotting quantum dynamics at multiple time points.
, Nat Commun, Vol: 16 -
Conference paperWebber-Date A, Rowley M, Osborn PF, et al., 2025,
A quantum-classical cold atom system for inertial navigation
, ISSN: 0277-786XA cold atom system for an inertial navigation system (INS) demonstrator utilising atom interferometry is presented. Laser-cooled rubidium-87 atoms in a grating magneto-optical trap (gMOT) are used to measure acceleration along a single axis. This system demonstrates a novel technique in quantum-enabled navigation which could offer significant improvement in precision and reduction in the drift present in classical INSs. Ruggedised lasers and control electronics allow potential deployment in maritime navigation in global navigation satellite system (GNSS) denied environments. Considerations are made towards a pathway for modular expansion and development of the system to 6-axis operation.
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Journal articleCryer-Jenkins E, Leung A, Rathee H, et al., 2025,
Brillouin-Mandelstam scattering in telecommunications optical fiber at millikelvin temperatures
, APL Photonics, Vol: 10, ISSN: 2378-0967Brillouin–Mandelstam scattering is a strong and readily accessible optical nonlinearity, enabling a wide array of applications and research directions. For instance, the three-wave mixing process has been employed to great success in narrow-linewidth lasers, sensing applications, microscopy, and signal processing. While most of these avenues focus on room temperature operation, there is now increasing interest in cryogenic operation owing to the scattering mechanism’s significant potential for applications and fundamental physics at low temperatures. Here, we measure the Brillouin scattering spectrum in standard single-mode telecommunication optical fibers at millikelvin temperatures using a closed-cycle dilution refrigerator and optical heterodyne detection. Our experiments are performed with a cryostat temperature from 50 mK to 27 K, extending previously reported measurements that utilized liquid helium-4 cryostats with temperatures greater than 1 K. At millikelvin temperatures, our experiment observes coherent acoustic interactions with microscopic defects in the amorphous material—two-level-systems (TLSs)—which has not been previously observed in optical fibers. The measured behavior of the linewidth with temperature is in agreement with the well-established models of ultrasonic attenuation in amorphous materials comprising a background intrinsic scattering, thermally activated scattering, and incoherent and coherent TLS interactions. This work provides a foundation for a wide range of applications and further research, including sensing applications, new approaches to investigate TLS physics, and Brillouin-scattering-based quantum science and technology.
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Conference paperVanner MR, 2025,
Towards quantum science and technology with Brillouin-Mandelstam scattering
, ISSN: 0277-786XBrillouin-Mandelstam scattering offers several favourable properties to control sound with light at a quantum mechanical level. In particular, the high acoustic frequencies, acoustic mode selectivity, and low optical absorption provide a promising route towards this goal whilst also overcoming several current hindrances within optomechanics. Utilizing these properties, some of our main results in this direction include: the first observation of Brillouin optomechanical strong coupling, studying the second-order coherence across the Brillouin lasing threshold, and, we’ve performed heralded single-phonon addition and subtraction to a thermal state of the acoustic field observing the resulting non-Gaussianity with a precision that advanced the forefront of optics-based mechanical state tomography. More recently, we’ve demonstrated that laser cooling may be enhanced via zero-photon detection, and we’ve characterized the Brillouin scattering response in optical fibre at millikelvin temperatures. This talk will cover these results, what they enable, and the broader direction of our lab including the prospects of this platform for quantum science and technology.
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Journal articleWang J, Driver T, Franz PL, et al., 2025,
Probing Electronic Coherence between Core-Level Vacancies at Different Atomic Sites
, Physical Review X, Vol: 15The detailed understanding of electronic coherence in quantum systems requires measurements on the attosecond timescale. Attosecond x-ray pulses enable the study of electronic coherence in core-excited molecular systems. Here we report on the coherent motion of electrons in the 1,1-difluoroethylene ion following ionization of the K shell of the two nonequivalent carbon sites with a subfemtosecond x-ray pulse. Using the angular streaking technique to track the Auger-Meitner decay, we observe temporal modulations of the emission, indicating the electronic coherence of the core-excited ionic states, and extract a 6.5±0.8 fs average lifetime of the core-level vacancies. A quantum-mechanical model is employed to interpret the measurement, and we find the observed temporal modulations are independent of charge density oscillations. This work opens a new regime of coherent electronic motion, beyond charge migration, where electronic coherence manifests in the nonlocal quantum correlation between atomic sites while charge density oscillation is absent. Our results broaden the landscape of electronic coherence in molecular systems.
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Journal articleGerry CC, Birrittella RJ, Alsing PM, et al., 2024,
Non-classicality and the effect of one photon.
, Philos Trans A Math Phys Eng Sci, Vol: 382The quantum interference effects of mixing the most non-classical states of light, number states, with the most classical-like of pure field states, the coherent state, are investigated. We demonstrate how the non-classicality of a single photon when mixed with a coherent field can transform the statistical properties of the output and further demonstrate that the entanglement of the output is independent of the coherent state amplitude.This article is part of the theme issue 'The quantum theory of light'.
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Journal articleWhite A, Popa S, Mellado Munoz J, et al., 2024,
Slow molecular beams from a cryogenic buffer gas source
, Physical Review Research, Vol: 6, ISSN: 2643-1564We study the properties of a cryogenic buffer gas source that uses a low temperature two-stage buffer gas cell to produce very slow beams of ytterbium monofluoride molecules. The molecules are produced by laser ablation inside the cell and extracted into a beam by a flow of cold helium. We measure the flux and velocity distribution of the beam as a function of ablation energy, helium flow rate, cell temperature, and the size of the gap between the first and second stages of the cell. We also compare the velocity distributions from one-stage and two-stage cells. The one-stage cell emits a beam with a speed of about 82 m s¯¹ and a translational temperature of 0.63 K. The slowest beams are obtained using the two-stage cell at the lowest achievable cell temperature of 1.8 K. This beam has a peak velocity of 56 m s¯¹ and a flux of 9×10⁹ ground state molecules per steradian per pulse, with a substantial fraction at speeds below 40 m s¯¹. These slow molecules can be decelerated further by radiation pressure slowing and then captured in a magneto-optical trap.
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Journal articleOrozco Ruiz M, Le NH, Mintert F, 2024,
Quantum control without quantum states
, PRX Quantum, ISSN: 2691-3399We show that combining ideas from the fields of quantum invariants and of optimal control can be used to design optimal quantum control solutions without explicit reference to quantum states. We describe how control problems for state preparation and the realization of propagators can be formulated in this approach, and we provide explicit control solutions for a spin chain with an extended Ising Hamiltonian. The states considered for state-preparation protocols include eigenstates of Hamiltonians with more than pairwise interactions, and these Hamiltonians are also used for the definition of target propagators. The cost of describing suitable time-evolving operators grows only quadratically with the system size, allowing us to construct explicit control solutions for up to 50 spins. While sub-exponential scaling is obtained only in special cases, we provide several examples that demonstrate favourable scaling beyond the extended Ising model.
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Journal articleFerte A, Austin D, Johnson AS, et al., 2024,
Signature of Attochemical Quantum Interference upon Ionization and Excitation of an Electronic Wave Packet in Fluorobenzene
, PHYSICAL REVIEW LETTERS, Vol: 133, ISSN: 0031-9007 -
Journal articleVylegzhanin A, Nic Chormaic S, Brown DJ, 2024,
Rydberg electromagnetically induced transparency based laser lock to Zeeman sublevels with 0.6 GHz scanning range.
, Rev Sci Instrum, Vol: 95We propose a technique for frequency locking a laser to the Zeeman sublevel transitions between the 5P3/2 intermediate and 32D5/2 Rydberg states in 87Rb. This method allows for continuous frequency tuning over 0.6 GHz by varying an applied external magnetic field. In the presence of the applied field, the electromagnetically induced transparency (EIT) spectrum of an atomic vapor splits via the Zeeman effect according to the strength of the magnetic field and the polarization of the pump and probe lasers. We show that the 480 nm pump laser, responsible for transitions between the Zeeman sublevels of the intermediate state and the Rydberg state, can be locked to the Zeeman-split EIT peaks. The short-term frequency stability of the laser lock is 0.15 MHz, and the long-term stability is within 0.5 MHz. The linewidth of the laser lock is ∼0.8 and ∼1.8 MHz in the presence and absence of the external magnetic field, respectively. In addition, we show that in the absence of an applied magnetic field and adequate shielding, the frequency shift of the lock point has a peak-to-peak variation of 1.6 MHz depending on the polarization of the pump field, while when locked to Zeeman sublevels, this variation is reduced to 0.6 MHz. The proposed technique is useful for research involving Rydberg atoms, where large continuous tuning of the laser frequency with stable locking is required.
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Journal articleHanif F, Das D, Halliwell J, et al., 2024,
Testing Whether Gravity Acts as a Quantum Entity When Measured
, PHYSICAL REVIEW LETTERS, Vol: 133, ISSN: 0031-9007 -
Journal articleWang P, Kwon H, Luan C-Y, et al., 2024,
Snapshotting quantum dynamics at multiple time points
, NATURE COMMUNICATIONS, Vol: 15 -
Journal articlePitchford A, Rakhubovsky AA, Mukherjee R, et al., 2024,
Bayesian optimization of non-classical optomechanical correlations
, QUANTUM SCIENCE AND TECHNOLOGY, Vol: 9, ISSN: 2058-9565 -
Journal articleSchofield RC, Fu M, Clarke E, et al., 2024,
Bose–Einstein condensation of light in a semiconductor quantum well microcavity
, Nature Photonics, Vol: 18, ISSN: 1749-4885When particles with integer spin accumulate at low temperature and high density, they undergo Bose–Einstein condensation (BEC). Atoms, magnons, solid-state excitons, surface plasmon polaritons and excitons coupled to light exhibit BEC, which results in high coherence due to massive occupation of the respective system’s ground state. Surprisingly, photons were shown to exhibit BEC recently in organic-dye-flled optical microcavities, which—owing to the photon’s low mass—occurs at room temperature. Here we demonstrate that photons within an inorganic semiconductor microcavity also thermalize and undergo BEC. Although semiconductor lasers are understood to operate out of thermal equilibrium, we identify a region of good thermalization in our system where we can clearly distinguish laser action from BEC. Semiconductor microcavities are a robust system for exploring the physics and applications of quantum statistical photon condensates. In practical terms, photon BECs ofer their critical behaviour at lower thresholds than lasers. Our study shows two further advantages: the lack of dark electronic states in inorganic semiconductors allows these BECs to be sustained continuously; and quantum wells ofer stronger photon–photon scattering. We measure an unoptimized interaction parameter ( g̃ ≳ 10–3), which is large enough to access the rich physics of interactions within BECs, such as superfuid light.
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Journal articleRuberti M, Averbukh V, Mintert F, et al., 2024,
Bell test of quantum entanglement in attosecond photoionization
, Physical Review X, Vol: 14, ISSN: 2160-3308Attosecond physics enables the study of ultrafast coherent electron dynamics in matter upon photoexcitation and photoionization, revealing spectacular effects such as hole migration and coherentAuger dynamics in molecules. In the photoionization scenario, there has been a strong focus onprobing the physical manifestations of internal quantum coherence within the individual parent ionand photoelectron systems. However, quantum correlations between these two subsystems emergingfrom attosecond photoionization events have thus far remained much more elusive. In this work, wedesign theoretically and model numerically a direct probe of quantum entanglement in attosecondphotoionization in the form of a Bell test. We simulate from first principles a Bell test protocolfor the case of noble gas atoms photoionized by ultrashort, circularly polarized infrared laser pulsesin the strong-field regime predicting robust violation of the Bell inequality. This theoretical resultpaves the way for the direct observation of entanglement in the context of ultrafast photoionizationof many-electron systems. Our work provides a novel perspective on attosecond physics directedtoward the detection of quantum correlations between systems born during attosecond photoionization and unraveling the signatures of entanglement in ultrafast coherent molecular dynamics,including in the chemical decomposition pathways of molecular ions.
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Journal articleYu S, Jia Z, Zhang A, et al., 2024,
Shedding light on the future: exploring quantum neural networks through optics
, Advanced Quantum Technologies, ISSN: 2511-9044At the dynamic nexus of artificial intelligence and quantum technology, quantum neural networks (QNNs) play an important role as an emerging technology in the rapidly developing field of quantum machine learning. This development is set to revolutionize the applications of quantum computing. This article reviews the concept of QNNs and their physical realizations, particularly implementations based on quantum optics. The integration of quantum principles with classical neural network architectures is first examined to create QNNs. Some specific examples, such as the quantum perceptron, quantum convolutional neural networks, and quantum Boltzmann machines are discussed. Subsequently, the feasibility of implementing QNNs through photonics is analyzed. The key challenge here lies in achieving the required non-linear gates, and measurement-induced approaches, among others, seem promising. To unlock the computational potential of QNNs, addressing the challenge of scaling their complexity through quantum optics is crucial. Progress in controlling quantum states of light is continuously advancing the field. Additionally, it has been discovered that different QNN architectures can be unified through non-Gaussian operations. This insight will aid in better understanding and developing more complex QNN circuits.
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Journal articleLee JP, Avni T, Alexander O, et al., 2024,
Few-femtosecond soft X-ray transient absorption spectroscopy with tuneable DUV-Vis pump pulses
, Optica, Vol: 11, Pages: 1320-1323, ISSN: 2334-2536Achieving few-femtosecond resolution for a pump-probe experiment is crucial to measuring the fastest electron dynamics and for creating superpositions of valence states in quantum systems. However, traditional UV-Vis pump pulses cannot achieve few-fs durations and usually operate at fixed wavelengths. Here, we present, to our knowledge, an unprecedented temporal resolution and pump tuneability for UV-Vis-pumped soft X-ray transient absorption spectroscopy. We have combined few-fs deep-UV to visible tuneable pump pulses from resonant dispersive wave emission in hollow capillary fiber with attosecond soft X-ray probe pulses from high harmonic generation. We achieve sub-5-fs time resolution, sub-fs interferometric stability, and continuous tuneability of the pump pulses from 230 to 700 nm. We demonstrate that the pump can initiate an ultrafast photochemical reaction and that the dynamics at different atomic sites can be resolved simultaneously. These capabilities will allow studies of the fastest electronic dynamics in a large range of photochemical, photobiological and photovoltaic reactions.
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