III–V quantum dots (QDs) grown by epitaxy are a typical zero-dimensional semiconductor confining electrons and holes with discrete energy levels. Charges, spins, and excitons in QDs can be used to implement qubits for quantum information processing. The radiative recombination of an exciton (electron–hole pair) in a single QD yields coherent single-photon emission. The presence of a resident carrier allows for the deterministic mapping between the stationary spin state and the flying photon polarization, enabling an efficient spin–photon interface. Moreover, QDs can be integrated into on-chip nanophotonic structures, including cavities and waveguides. Owing to these features, III–V QDs have shown great potential for the scalable quantum network. In the past two decades, substantial progress in QD growth techniques, exciton modulation methods, and nanophotonic device fabrication has led to the development of high-performance quantum photonic devices. However, several key challenges still exist, such as the growth of high-quality QDs operating at the telecom band, precise control and enhancement of cavity–QD coupling strength, and deterministic integration of QDs into photonic circuits. This review explores recent progress and applications of III–V QDs, including state-of-the-art growth techniques, advanced exciton control schemes such as resonance fluorescence, investigations of cavity quantum electrodynamics, and single-photon routing through waveguides. In the end, the prospects for realizing a QD-based quantum photonic network for practical applications are also discussed.

Quantum electrodynamics of graphene landau levels in a deep-sub-wavelength hyperbolic phonon polariton cavity

In this work, we map noisy intermediate-scale quantum (NISQ)-friendly implementations of the noninteracting quantum cellular automata (QCA) to a circuit quantum electrodynamics (cQED) hardware. We perform both noiseless and noisy simulations of the QCA one-particle sector, namely, the quantum walk, on N -cycles and N × N torus graphs. Moreover, within this framework, we also investigate the search problem and present a circuit for preparing the state (i.e., the Dicke state with Hamming weight 1) using only 1 iSWAP gates and no ancilla qubits. The noiseless simulations are conducted with the Qiskit Aer simulator, while the noisy simulations with C12 Quantum Electronics’ in-house noisy emulator, . We benchmark the performance of our implementations by analyzing the simulations via relevant metrics and quantities such as the state count distributions, the Hellinger fidelity, the ℓ 1 distance, the hitting time, and the success probability. Our results demonstrate that the QCA framework, in combination with cQED processors, holds promise as an effective platform for early NISQ implementations of quantum walk and quantum walk search algorithms.

ABSTRACT We investigate how parity‐time () symmetry influences photon blockade in an atom‐coupled dual‐cavity quantum electrodynamics (QED) system, with a focus on distinguishing the underlying mechanisms. Statistical analysis demonstrates that photon blockade exhibits qualitatively distinct behaviors in the ‐symmetric and symmetry‐broken phases, thereby providing a clear signature of the phase transition. In this ‐symmetric structure, the two‐level atom provides the required nonlinearity, while cavity‐cavity coupling under ‐symmetric control cooperatively enhances photon antibunching, leading to simultaneous photon blockade in both the passive and the active cavities. These phenomena are comprehensively analyzed using both analytical solutions of the Schrödinger equation and numerical simulations of the master equation. Comparisons with non‐‐symmetric configurations reveal that symmetry significantly enhances photon antibunching, mean photon number and promotes cooperative blockade behavior across both cavities. In contrast to conventional photon blockade schemes, our approach remains effective under weak coupling and weak nonlinearity conditions, offering a robust and tunable pathway toward realizing high‐performance single‐photon sources in non‐Hermitian quantum systems.

Electron energy loss spectroscopy of oriented targets and magnetic transitions.

ABSTRACT We present a versatile dielectric platform for studying chiral light–matter interaction and cavity quantum electrodynamics, based on high bend transmittance waveguide (HBT WG) modes of triangular‐lattice photonic crystals (Tri‐PhCs). The demonstration of chiral coupling is realized by employing two Tri‐PhC zigzag interface waveguides which offer a simplified geometry in the first place. Compared to previous honeycomb‐lattice systems, Tri‐PhC zigzag waveguides provide at least twice the effective chiral area for quantum dot (QD) interaction and support accessible slow‐light modes that are crucial for light–matter interaction. Integrating self‐assembled QDs, we experimentally demonstrate chiral photon routing in Z‐shaped Tri‐PhC HBT WGs, confirming robust directional photon transport. Additionally, we incorporate a whispering‐gallery‐mode cavity‐waveguide structure to achieve Purcell‐enhanced on‐chip single‐photon emission, with a Purcell factor of 4 and spin‐dependent directional contrast of 82%. Our results show the potential of Tri‐PhC‐based topological waveguides as a promising, scalable platform for low‐loss, high‐chirality quantum photonic devices.

Neutral-atom arrays and optical cavity quantum electrodynamics systems have developed in parallel as central pillars of modern experimental quantum science1-3. Although each platform has shown exceptional capabilities-such as high-fidelity quantum logic4-7 in atom arrays and strong light-matter coupling in cavities8-10-their combination holds promise for realizing fast and non-destructive atom measurement11, building large-scale quantum networks12-17 and engineering hybrid atom-photon Hamiltonians18-20. However, so far, experiments integrating the two platforms have been limited to spatially interfacing the entire atom array with one global cavity mode21-26, a configuration that constrains addressability, parallelism and scalability. Here we introduce the cavity-array microscope, an experimental platform where each individual atom is strongly coupled to its own individual cavity across a two-dimensional array of over 40 modes. Our approach requires no nanophotonic elements26,27, and instead uses a free-space cavity geometry with intra-cavity lenses28,29 to realize above-unity peak cooperativity with micrometre-scale mode waists and spacings, compatible with typical atom-array length scales while keeping atoms far from dielectric surfaces. We achieve homogeneous atom-cavity coupling and show fast, non-destructive, parallel readout on millisecond timescales, including through a fibre array as a proof of principle for networking applications30. As an outlook, we realize a next-generation iteration of the platform with over 500 cavities and a nearly 10-fold improvement in finesse. Our work unlocks the regime of many-cavity quantum electrodynamics and opens an unexplored frontier of large-scale quantum networking with atom arrays.

We report the potential energy curve, the diagonal Born-Oppenheimer, non-adiabatic mass, relativistic, and leading-order quantum-electrodynamical (QED) corrections for the ground electronic state of the helium dimer cation; the higher-order QED and finite-nuclear size effects are also estimated. The computations are carried out with an improved error control and over a broader configuration range compared to earlier work [D. Ferenc, V. I. Korobov, and E. Mátyus, Phys. Rev. Lett. 125, 213001 (2020)]. As a result, all rovibrational bound states are reported with an estimated accuracy of 0.005 cm − 1 .

Manipulation of excitonic emission properties is important for numerous photonic applications. Of particular interest are developing easy-to-implement yet effective approaches for controlling the radiation dynamics and directionality of spin-forbidden dark excitons (XD) in two-dimensional semiconductors. Here, we investigate the spectral, temporal, and directional characteristics of room-temperature XD emission from a tungsten diselenide monolayer coupled to a dissipative plasmonic nanocavity. Under resonant plasmon-exciton coupling, the radiative decay rate of XD is accelerated by nearly four orders of magnitude, and correspondingly, the XD lifetime is shortened to a subnanosecond level, making it comparable to that of bright excitons. Fitting the measured lifetimes with a Purcell-formalism–based cavity quantum electrodynamics model allows estimating of the intrinsic room-temperature XD lifetime to be about 24 ± 2.3 microseconds. Furthermore, the measured radiation patterns of the dark excitons show that subtle variations in the nanocavity orientation can effectively tailor the XD emission directionality, important for quantum technologies and optoelectronics applications.

Vortex γ photons carrying orbital angular momenta (OAM) hold great potential for various applications. However, their generation remains a great challenge. Here, we successfully generate sub-MeV vortex γ photons via all-optical inverse Compton scattering of relativistic electrons colliding with a subrelativistic Laguerre-Gaussian laser. In principle, directly measuring the OAM of γ photons is challenging due to their incoherence and extremely short wavelength. Therein, we put forward a novel method to determine the OAM properties by revealing the quantum opening angle of vortex γ photons, since vortex particles exhibit not only a spiral phase but also transverse momentum according to the quantum electrodynamics theory. Thus, γ photons carrying OAM manifest a much larger angular distribution than those without OAM, which has been clearly observed in our experiments. This angular expansion is considered as an overall effect lying beyond classical theory. Our method provides the first experimental evidence for detecting vortex γ photons and opens a new perspective for investigating OAM-induced quantum phenomena in broad fields.

With the rapid development of nanophotonics and cavity quantum electrodynamics, there has been growing interest in how confined electromagnetic fields modify fundamental molecular processes such as electron transfer. In this paper, we revisit the problem of nonadiabatic electron transfer (ET) in confined electromagnetic fields studied in Semenov and Nitzan [J. Chem. Phys. 150, 174122 (2019)] and present a unified rate theory based on Fermi's golden rule. By employing a polaron-transformed Hamiltonian, we derive analytic expressions for the ET rate correlation functions that are valid across all temperature regimes and all cavity mode time scales. In the high-temperature limit, our formalism recovers the Marcus and Marcus-Jortner results, while in the low-temperature limit, it reveals the emergence of the energy gap law. We further extend the theory to include cavity loss by using an effective Brownian oscillator spectral density, which enables closed-form expressions for the ET rate in lossy cavities. As applications, we demonstrate two key cavity-induced phenomena: (i) resonance effects, where the ET rate is strongly enhanced with certain cavity mode frequencies, and (ii) electron-transfer-induced photon emission, arising from the population of cavity photon Fock states during the ET process. These results establish a general framework for understanding how confined electromagnetic fields reshape charge transfer dynamics and suggest novel opportunities for controlling and probing ET reactions in nanophotonic environments.

The ionization potential (IP) of radium monofluoride (RaF) was measured to be 4.969(2)[10] eV, revealing a relativistic enhancement in the series of alkaline earth monofluorides. The results are in agreement with a relativistic coupled-cluster prediction of 4.981(7) eV, incorporating up to quantum electrodynamics corrections. Using the same computational methodology, an improved calculation for the dissociation energy ( D 0 ) of 5.54(5) eV is presented. This confirms that RaF joins the group of diatomic molecules for which D 0 > IP , paving the way for precision control and interrogation of its Rydberg states.

Controlling nanoscale interactions to suppress aggregation from short-range attractive forces is a key problem in nanoengineering. Here, we demonstrate a route to modulate Casmir-Lifshitz interactions between anisotropic nanoparticles and magnetic fluids. By semiclassical quantum electrodynamics, we study ground state dispersion forces for cylindrical dielectric nanorods made of polystyrene (PS) and zinc oxide (ZnO) embedded in toluene-based host media with gold-coated magnetite nanoparticles and also predict magnetic contributions to the fully retarded excited state interaction. The variation in magnetic permeability enables tuning between repulsive and attractive interactions, and measurable magnetic Casimir traps are predicted between a pair of ZnO-PS nanoparticles whose equilibrium position can be modulated over an order of magnitude with a small variation in the size of the magnetite nanoparticle. This provides an alternative magnetic Casimir-effect pathway to reversibly tune quantum electromagnetic forces at the nanoscale for the assembly and enhancement of colloidal stability.

We report the modulation of molecular charge transferin a bay-substitutedperylene diimide derivative embedded in a planar distributed Braggreflector microcavity. Angle-resolved reflectance spectra confirmthe formation of upper and lower polaritons with clear Rabi splitting,indicating strong coupling between the cavity mode and molecular excitons.Using broadband transient absorption spectroscopy, we compare theultrafast dynamics of cavity and non-cavity films. While excited-stateabsorption and stimulated emission pathways remain largely unchanged,kinetic modeling reveals a moderate increase in the charge transferrate and yield under strong coupling. This enhancement is attributedto a reduction in the effective driving force via the formation ofthe lower polariton, placing the system deeper into the Marcus invertedregime. Our results demonstrate a promising non-chemical method leveragingcavity quantum electrodynamics to modulate charge separation processesin molecular semiconductors.

The thermodynamic and geometric properties of the Euler–Heisenberg BH in nonlinear quantum electrodynamics (QED) are investigated under the incorporation of Barrow entropy, which is assumed to encode quantum-gravity-induced fractal deformations of the event horizon. A richer thermodynamic phase structure than the classical Reissner–Nordström case is found, as the combined effects of strong-field QED vacuum polarization and Barrow fractal entropy corrections are considered. The heat capacity is observed to undergo a sequence of transitions, changing from negative to positive values, diverging at a critical point, and becoming positive again for large horizon radii, which indicates the presence of a second-order phase transition. The Hawking temperature is shown to develop both a minimum and a maximum, the free-energy–temperature curve is demonstrated to exhibit double points signaling metastability and phase coexistence, and a van der Waals-like behavior is seen in the pressure–temperature plane. Meanwhile, curvature diagnostics reveal that the Kretschmann scalar remains finite, whereas the Ricci scalar displays a divergence, establishing a correspondence between thermodynamic and geometric critical behavior. Thus, a physically consistent framework to probe horizon microstructure under quantum-gravity inspired corrections is provided through Barrow entropy, and the Euler–Heisenberg model is shown to serve as a viable setting to explore the interplay between nonlinear electrodynamics and fractal horizon geometry.

Kaonic atoms, formed when a negatively charged kaon replaces an electron, provide a unique laboratory to test fundamental interactions at low energies. EXKALIBUR (EXtensive Kaonic Atoms research: from LIthium and Beryllium to URanium) is a program to perform systematic, high-precision X-ray spectroscopy of selected kaonic atoms across the periodic table at the DAФNE accelerator at the National Laboratory of Frascati. Here, we outline its detector-driven strategy: silicon drift detectors for 10–40 keV transitions in light targets (Li, Be, B, O), CdZnTe detectors for 40–300 keV lines in intermediate-Z systems (Mg, Al, Si, S), and a high-purity germanium detector for high-Z atoms (Se, Zr, Ta, Mo, W, Pb), complemented by VOXES, a high-resolution crystal spectrometer for sub eV studies. EXKALIBUR plans to (i) reduce the charged-kaon mass uncertainty below 10 keV, (ii) produce a database of nuclear shifts and widths to constrain multi-nucleon K--nucleus interactions models, and (iii) provide precision data for testing bound-state quantum electrodynamics in strong fields. We summarize the planned measurements and expected sensitivities within DAФNE luminosities.

We review recent applications of nonlocal effective field theory, particularly focusing on nonlocal chiral effective theory and nonlocal quantum electrodynamics (QED), as well as an extension of nonlocal effective theory to curved spacetime. For the chiral effective theory, we discuss the calculation of generalized parton distributions (GPDs) of the nucleon at nonzero skewness, along with the corresponding gravitational (or mechanical) form factors, within the convolution framework. In the QED application, we extend the nonlocal formulation to construct the most general nonlocal QED interaction, in which both the propagator and fundamental QED vertex are modified due to the nonlocal Lagrangian, while preserving the Ward–Green–Takahashi identities. For consistency with the modified propagator, a solid quantization is proposed, and the nonlocal QED is applied to explain the lepton g−2 anomalies without the introduction of new particles beyond the standard model. Finally, with an extension of the chiral effective action to curved spacetime, we investigate the nonlocal energy–momentum tensor and gravitational form factors of the nucleon with a nonlocal pion–nucleon interaction.

Modern spectroscopic techniques enable the determination of the spacing between rovibrational levels of H2 with a relative accuracy of approximately 10-11. At this extreme level of precision, subtle quantum electrodynamic (QED) effects, such as electron self-interaction and vacuum polarization, are probed. A theoretical model aiming to achieve similar accuracy must precisely describe not only these relatively small QED effects but also the more significant contributions related to electron correlation, coupling between electronic and nuclear motions, and relativistic effects. Although the hydrogen molecule exhibits most of the phenomena found in larger molecules, it is simple enough to meet the requirements mentioned above. In this article, we report on enhancements to the current capabilities of quantum mechanical calculations for the hydrogen molecule. We present a method based on exponential functions that fully captures electron correlation or, more broadly, interparticle correlation, enabling a comprehensive description of effects related to nuclear motion. Specifically, we solve the four-particle Schrödinger equation without invoking commonly used approximations such as the one-electron or the Born-Oppenheimer approximation. The only source of nonrelativistic energy error comes from the finite size of the basis set. The explicitly correlated nonadiabatic wave function used here is then employed to determine the relativistic and QED effects. As a result, the dissociation energy for the lowest rovibrational levels in the electronic ground state of H2 has been obtained with a relative accuracy of 7 × 10-10, while the frequencies of intervals between these levels have been determined with sub-MHz accuracy, corresponding to a relative accuracy of 3 × 10-9. In consequence, the discrepancies between the highest precision measurements and earlier theoretical predictions have been resolved.

Topological quantum electrodynamics in synthetic non-Abelian gauge fields

Photonic time crystals host a variety of intriguing phenomena, from wave amplification and mixing to exotic band structures, all stemming from the time-periodic modulation of optical properties. While these features have been well described classically, their quantum manifestation when coupled to an atomic electric dipole has remained elusive. Here, we introduce a quantum electrodynamical model of photonic time crystals that reveals a deeper connection between classical and quantum pictures: the classical momentum gap arises from a localization-delocalization quantum phase transition in a Floquet-photonic synthetic lattice. Leveraging an effective Hamiltonian perspective, we pinpoint the critical momenta and highlight how classical exponential field growth manifests itself as wave-packet acceleration in the quantum synthetic space. Remarkably, when a two-level atom is embedded in such a photonic time crystal, its Rabi oscillations undergo irreversible decay to a half-and-half mixed state—a previously unobserved phenomenon driven by photonic delocalization within the momentum gap, even with just a single frequency mode. Our findings establish photonic time crystals as versatile platforms for studying nonequilibrium quantum photonics and suggest new avenues for controlling light matter interactions through time domain engineering.