Quantum key distribution (QKD) enables information-theoretic secure communication, yet its ultimate tolerance to noise and achievable transmission distance remain fundamentally constrained. We establish the maximum quantum bit error rate (QBER) compatible with secure QKD and derive corresponding upper bounds on communication distance. Our results follow from a fundamental capacity threshold for qubit Pauli channels and apply to protocols based on two or more mutually unbiased bases, using either single-photon or weak coherent sources. By connecting information-theoretic limits to realistic physical noise models, we obtain universal bounds on achievable distances in fiber and free-space links, including diffraction-limited constraints relevant to deep-space quantum communications. These findings clarify the ultimate noise robustness of QKD and delineate the fundamental boundaries of secure quantum communication.

Quantum networks enable a variety of quantum information processing tasks, where multiuser quantum communication is one of the important objectives. Quantum cryptographic conferencing (QCC) serves as an essential solution to establish secure keys to realize secure multiuser communications. However, existing QCC implementations have been fundamentally limited by the low probability of multiuser coincidence detection to measure or construct the Greenberger-Horne-Zeilinger (GHZ) entangled state. In this Letter, we report the experimental realization of QCC eliminating the need for coincidence detection, where the GHZ state is constructed by correlating detection events occurring within the coherence time, thereby greatly enhancing the success probability of GHZ-state measurement. Meanwhile, to establish and maintain high-visibility GHZ measurement among three independent users, we developed a three-party phase compensation scheme combined with precise temporal and polarization alignment within a time-bin-phase encoding framework. Furthermore, we designed an efficient pairing strategy to simplify subsequent data processing and enhance processing efficiency. Based on these techniques, we successfully performed QCC experiments over total loss of 66.3 dB, with the channel loss of 51.24 dB, achieving secure key rates of $5.4\mathrm{bit}/\mathrm{s}$, whereas previous QCC experiments have been limited to 100 km. The results establish a new regime of scalable, multiuser quantum communication and paving the way for metropolitan quantum networks.

Even 50 years after the discovery of a positron annihilation line from the inner Galaxy, no class of astrophysical sources has emerged as a definitive explanation for both the emission morphology and flux. Positrons produced by dark matter annihilation or decay have been proposed, but the mass of any such candidate is constrained by continuum $\gamma$-ray emission at energies $>511\mathrm{keV}$. Earlier analyses have claimed that this emission requires that the positrons have kinetic energies less than a few MeV at injection, disfavoring both much of the dark matter parameter space and many potential compact astrophysical source classes such as pulsars. However, these constraints were not based on a full forward model of the absolute flux of the $\gamma$-ray line and continuum data, and did not marginalize over uncertainties about the relative angular distributions of the line and continuum. Here we describe an improved analysis that overcomes these limitations, and show that constraints on the injection energy are much weaker than previously claimed; even under conservative assumptions the data are consistent with initial energies up to $\sim 110\mathrm{MeV}$ from INTEGRAL/SPI data alone, and up to $\sim 55\mathrm{MeV}$ when including COMPTEL and EGRET data, subject to cross-normalization between them and INTEGRAL.

We propose a new mechanism for the formation of seeds of supermassive black holes at early cosmic epochs. Our scenario explores density fluctuations that are enhanced relative to $\mathrm{\Lambda }\mathrm{CDM}$ expectations, but with amplitudes that are not large enough to form primordial black holes, and that can still lead to collapsed dark matter halos at very early times. For halos forming prior to $1+z\approx 200$, the cosmic microwave background (CMB) is energetic enough to suppress the formation of molecular hydrogen, hence preventing cooling and fragmentation, as a consequence of which baryons falling into the potential well of the halo may undergo “direct collapse” into a black hole. We show, using a few illustrative models, how this mechanism may account for the abundance of high-redshift black holes inferred from observations by the James Webb Space Telescope while remaining consistent with limits from CMB spectral distortions. Limits on the primordial power spectrum are also derived by requiring that the universe not reionize too early.

We compute the gravitational interaction of two coalescing compact objects at sixth post-Newtonian order in the static limit, employing the diagrammatic approach within the effective field theory framework of general relativity. The calculation requires the evaluation of six-loop Feynman diagrams that are mapped onto two-point integrals with a gauge-theory-like structure, which are computed here for the first time. The resulting seventh-order contribution in Newton’s constant is finite in three space dimensions. This result provides the most technically demanding missing ingredient for the determination of the conservative dynamics of the gravitational two-body system at sixth post-Newtonian order.

We calculate all three-loop, five-point, massless planar Feynman integral families in the dimensional regularization scheme. This is a new milestone in Feynman integral computations. The analysis covers four distinct families of Feynman integrals for this configuration, for all of which we derive the canonical differential equations. Our results also confirm a prediction on the three-loop five-point alphabet. The boundary values are analytically determined. These differential equations offer a promising route toward efficient high-precision evaluation of the integrals. Our work establishes the foundation for next-to-next-to-next-to-leading-order calculations of the production of three massless final states, as well as corresponding bootstrap studies in gauge theories.

We show that the infinite tower of hard exclusive amplitudes in holographic light-front QCD leads to a spectral generator $G(\alpha ,\lambda )$ that encodes the full Regge spectrum. The construction assumes a Poisson distribution of Fock-state components, where $\lambda$ represents the average parton multiplicity above the valence configuration. The resulting generator yields a Regge spectrum invariant under continuous $\lambda$ deformations. Its even- and odd-twist projections yield the meson and baryon form factors with a single value of $\lambda$, fixed by the pion charge radius, which in turn determines the full $Q^2$ dependence. The constituent counting rules for both sectors follow from the structure of the spectral generator, which also provides a compact analytic representation of parton distributions.

QCD collinear factorization allows coherent hard exclusive reactions to reveal the quark-gluon structure of light nuclei, enabling their 3D tomography. In this Letter, we investigate elastic form factors and deeply virtual Compton scattering on a helium-4 target. We achieve unprecedented theoretical precision for this type of analysis by constraining generalized parton distributions at next-to-leading order in ${\alpha }_s$, incorporating kinematic twist corrections, and utilizing full evolution equations. Ultimately, we present the first tomography of a light nucleus, revealing distinct transverse spatial distributions of quarks and gluons.

We present results from a high precision experimental study of the nuclear modification of the longitudinal ($F_L$) to transverse ($F_1$) structure function ratio for bound nucleons in the resonance region. The inclusive electron scattering cross sections were measured in Jefferson Lab Experimental Hall C on carbon and deuterium nuclei for a large range of kinematics, allowing for separations of the longitudinal and transverse structure functions to be performed at a range of four-momentum transfer values $0.5\le Q^2\le 3.75{\mathrm{GeV}}^2$. In contrast to the significant body of measurements of the nuclear modification of the $F_2$ structure function in the deep inelastic scattering region, there is very little on $F_L$ and $R=F_L/2x{F}_1$ in the region of the nucleon resonances. In this Letter we present measurements of the nuclear effect on $R$ for ${}^{12}\mathrm{C}$ ($R_C$) relative to deuterium ($R_D$). These results indicate regions in which in $R_C>R_D$, requiring that the nuclear modifications be different in all three structure functions, $F_2$, $F_1$, and $F_L$.

We demonstrate a technique for spatially resolved temperature measurement utilizing Rydberg Doppler broadening thermometry. This method employs two focused laser beams arranged perpendicularly to excite laser-cooled atoms from the ground state to a Rydberg state via a two-photon absorption process. Temperature is obtained through Doppler broadening of the spectral line. The perpendicular configuration allows for selective probing of a specific position within the atomic cloud, enabling localized temperature measurement. This technique, in principle, offers a temperature resolution on the order of nK, attributed to the exceptionally narrow natural linewidth of the involved rubidium Rydberg transition line. Furthermore, the setup enables the measurement of position-velocity correlations within the cold atom ensemble. The velocity information is extracted through the Doppler shift, whereas the spatial information is inferred from the arrival time of ions detected by a channel electron multiplier detector. We use our method to measure the local temperature in a magneto-optical trap.

Ultracold molecules are becoming an increasingly important technology for quantum simulation, computation, and sensing, but their state preparation in large, low-entropy arrays remains a key challenge. We propose to deterministically load single molecules into optical tweezer arrays or lattices from either thermal or degenerate gases, with a high probability of occupying the tweezer’s motional ground state. Strong repulsion between microwave-shielded molecules prevents multiparticle occupancy. Our proposal represents a robust scheme for deterministic single molecule preparation directly in the motional ground state with expected fidelities exceeding 99% for small trap volumes and highly polar species. This method can be scaled to thousands of traps limited by the reservoir molecule number, opening the door to large, low-entropy polar molecule arrays for quantum computation, quantum simulation, and precision measurement.

We propose a qubit-oscillator platform based on the motional states of two interacting atoms in an optical tweezer. By stroboscopically modulating an engineered trap with tunable anharmonicity, we implement a complete set of bosonic operations and their qubit-controlled counterparts with high fidelity. This motional control enables accurate detection of magnetic dipolar interactions with $\sim 10\mathrm{Hz}$ sensitivity in 1 s, reaching sub-Hz resolution within a few minutes in a $20\times 20$ tweezer array under realistic experimental imperfections. Our approach establishes a versatile platform for motional quantum control of two atoms, with applications to spin-boson physics and precision sensing of interaction potentials and trapping environments.

Gate-defined semiconductor quantum dots utilize fast electrical control to manipulate spin and charge states of individual electrons. Electrical pulse distortions can limit control fidelities but are difficult to measure at the device level. Here, we use detuning-axis pulsed spectroscopy to characterize baseband pulse distortions in a silicon double quantum dot. We extract the gate-voltage impulse response and apply a digital predistortion filter to eliminate pulse distortions on timescales longer than 1 ns. With the predistortion, we reduce the frequency chirp of coherent exchange oscillations in a singlet-triplet qubit. Our results suggest a scalable and tuning-efficient method for characterizing pulse distortions in quantum-dot spin qubits.

Wave transport in disordered media is obscured by complex multiple scattering, yet prior experiments lack precise, reconfigurable control over microscopic disorder potentials. Using photoaligned nematic liquid crystals, we implement programmable spatial optical potentials to deterministically tailor anisotropic branched light flow. With this platform, we experimentally verify the long-theorized generalized scaling law for the first-branch distance of branched wave transport—an unprecedented experimental milestone validating universal scaling across hydrodynamic, acoustic, atomic, and electronic wave systems. In the extreme anisotropy regime, we observe striking directional light channeling induced by anomalous symmetry-breaking velocity diffusion: light propagates along preferred paths with fully suppressed transverse spreading in disordered media. Our reconfigurable liquid-crystal testbed enables controlled exploration of anisotropic stochastic wave dynamics, paving the way for disorder-guided on-chip photonics, scattering-robust endoscopic imaging, and adaptive optics for complex scattering environments.

The statistical properties of solar flare occurrence are critical for understanding coronal energy release, yet the nature of their underlying dynamics remains heavily debated. Analyzing over two decades of soft x-ray observations from a comprehensive geostationary operational environmental satellite (GOES) dataset, we demonstrate that flare waiting time distributions exhibit a previously unreported scale invariance under coarse graining by flare size. This self-similarity proves the existence of long-range temporal correlations between events. This finding is supported by a complementary multifractal analysis of the x-ray flux, which confirms the presence of intermittency and turbulentlike scaling. By ruling out independent event occurrence, these results establish new statistical constraints on solar flare dynamics and link their intermittent behavior to shared multiscale avalanche phenomena in complex systems.

The behavior of spin quantum in $\mathbf{k}$-space is key to identifying altermagnets (AMs) as the third kind of fundamental collinear magnetism. By contrast, noncollinear magnets—though abundant in nature—lack well-defined spin quantum numbers, and the resulting spin textures are often highly complex, which limits their potential for next-generation spintronic applications. Here we propose hyperspin, which lives in a higher-dimensional space, to address these drawbacks. Through analyzing the commutation relations between spin and Hamiltonian for a class of noncollinear magnets, we reveal that it is a hyperspin, rather than the usual spin, that commutes with Hamiltonian. Unexpectedly, these noncollinear magnets should also show collinear spin-split bands in $\mathbf{k}$-space like collinear AMs. We therefore classify such noncollinear magnets as hyperspin altermagnets (HAMs), as opposed to the usual collinear AMs. Our theory elucidates the fundamental physics of AMs and HAMs and provides a framework for exploring the wide range of noncollinear magnets that may possess other kinds of conserved quantities.

Physical entropy-driven true random number generators are essential for emerging probabilistic computing paradigms, but conventional implementations based on magnetic tunneling junctions have reached their performance plateaus limited by inherent tradeoffs and weak tunability. Here, autferroics, a sister branch of multiferroics, is proposed to construct true random number generators. Benefiting from its unique energy landscape due to strong seesaw-type magnetoelectricity, the performance of true random number generation can be significantly enhanced in autferroic tunneling junctions, verified by passing standard statistical tests. Furthermore, autferroics-based random number generators can exhibit multifield tunability and intrinsic multistate randomness, opening an avenue for efficient hardware realization of the complex-number arithmetic and simulation of probability distributions of quantum mixed states within stochastic circuits.