Understanding the entanglement of radiation in quantum field theory has been a long-standing challenge, with implications ranging from black hole thermodynamics to quantum information. We demonstrate how the case of the free fermion in $1+1$ dimensions reveals the details of the density matrix of the radiation produced by a moving mirror. Using the resolvent method rather than standard conformal field theory techniques we derive the Rényi entropies, modular Hamiltonian, and flow of the radiation and determine when mirrors generate unitary transformations.

Time-varying optical media, whose dielectric properties are actively modulated in time, introduce a host of novel effects in the classical propagation of light, and are of intense current interest. In the quantum domain, time-dependent media can be used to convert vacuum fluctuations (virtual photons) into pairs of real photons. We refer to these processes broadly as “dynamical vacuum effects” (DVEs). Despite interest for their potential applications as sources of quantum light, DVEs are generally very weak, presenting many opportunities for enhancement through modern techniques in nanophotonics, such as using media which support excitations such as plasmon and phonon polaritons. Here, we present a theory of weakly modulated DVEs in arbitrary nanostructured, dispersive, and dissipative systems. A key element of our framework is the simultaneous incorporation of time-modulation and “dispersion” through time-translation-breaking linear response theory. As an example, we use our approach to propose a highly efficient scheme for generating entangled surface polaritons based on time-modulation of the optical phonon frequency of a polar insulator.

We experimentally demonstrate the temporary removal of thermal photons from a microwave mode at 1.45 GHz through its interaction with the spin-polarized triplet states of photo-excited pentacene molecules doped within a $p$-terphenyl crystal at room temperature. The crystal functions electromagnetically as a narrowband cryogenic load, removing photons from the otherwise room-temperature mode via stimulated absorption. The noise temperature of the microwave mode dropped to ${50}_{-32}^{+18}\mathrm{K}$ (as directly inferred by noise-power measurements), while the metal walls of the cavity enclosing the mode remained at room temperature. Simulations based on the same system’s behavior as a maser (which could be characterized more accurately) indicate the possibility of the mode’s temperature sinking to $\sim 10\mathrm{K}$ (corresponding to $\sim 140$ microwave photons). These observations, when combined with engineering improvements to deepen the cooling, identify the system as a narrowband yet extremely convenient platform—free of cryogenics, vacuum chambers, and strong magnets—for realizing low-noise detectors, quantum memory, and quantum-enhanced machines (such as heat engines) based on strong spin-photon coupling and entanglement at microwave frequencies.

We discover the formation of a temporal boundary soliton (TBS) in close proximity of a temporal boundary, moving in a nonlinear optical medium, upon high-intensity pulse collision with the boundary. We show that the emergent TBS is unstable to perturbations caused by the cross-phase modulation between the TBS and the other soliton products of the collision and that such instability triggers colossal intensity fluctuations of the reflected pulse ensemble with unprecedented magnitudes of the normalized autocorrelation function for an even weakly fluctuating input pulse.

We predict a new mechanism to induce collective excitations and a nonequilibrium phase transition of fermionic superfluids via a sudden switch on of two-body loss, for which we extend the BCS theory to fully incorporate a change in particle number. We find that a sudden switch on of dissipation induces an amplitude oscillation of the superfluid order parameter accompanied by a chirped phase rotation as a consequence of particle loss. We demonstrate that when dissipation is introduced to one of the two superfluids coupled via a Josephson junction, it gives rise to a nonequilibrium dynamical phase transition characterized by the vanishing dc Josephson current. The dissipation-induced collective modes and nonequilibrium phase transition can be realized with ultracold fermionic atoms subject to inelastic collisions.

We experimentally determine isotropic and anisotropic $g$-factor corrections in lateral GaAs single-electron quantum dots. We extract the Zeeman splitting by measuring the tunnel rates into the individual spin states of an empty quantum dot for an in-plane magnetic field with various strengths and directions. We quantify the Zeeman energy and find a linear dependence on the magnetic field strength that allows us to extract the $g$ factor. The measured $g$ factor is understood in terms of spin-orbit interaction induced isotropic and anisotropic corrections to the GaAs bulk $g$ factor. Experimental detection and identification of minute band-structure effects in the $g$ factor is of significance for spin qubits in GaAs quantum dots.

It was recently proposed that there is a phase in thermal QCD (IR phase) at temperatures well above the chiral crossover, featuring elements of scale invariance in the infrared (IR). Here, we study the effective spatial dimensions $d_{\mathrm{IR}}$ of Dirac low-energy modes in this phase, in the context of pure-glue QCD. Our $d_{\mathrm{IR}}$ is based on the scaling of mode support toward thermodynamic limit, and hence is an IR probe. Ordinary extended modes, such as those at high energy, have $d_{\mathrm{IR}}=3$. We find $d_{\mathrm{IR}}<3$ in the spectral range whose lower edge coincides with ${\lambda }_{\mathrm{IR}}=0$, the singularity of spectral density defining the IR phase, and the upper edge with ${\lambda }_A$, the previously identified Anderson-like nonanalyticity. Details near ${\lambda }_{\mathrm{IR}}$ are unexpected in that only exact zero modes are $d_{\mathrm{IR}}=3$, while a thin spectral layer near zero is $d_{\mathrm{IR}}=2$, followed by an extended layer of $d_{\mathrm{IR}}=1$ modes. With only integer values appearing, $d_{\mathrm{IR}}$ may have a topological origin. We find similar structure at ${\lambda }_A$, and associate its adjacent thin layer ($d_{\mathrm{IR}}⪆2$) with Anderson-like criticality. Our analysis reveals the manner in which nonanalyticities at ${\lambda }_{\mathrm{IR}}$ and ${\lambda }_A$, originally identified in other quantities, appear in $d_{\mathrm{IR}}(\lambda )$. This dimension structure may be important for understanding the near-perfect fluidity of the quark-gluon medium seen in accelerator experiments. The role of ${\lambda }_A$ in previously conjectured decoupling of IR component is explained.

Atomiclike defects in solids are not considered to be identical owing to the imperfections of host lattice. Here, we found that even under ambient conditions, negatively charged nitrogen-vacancy (${\mathrm{NV}}^{-}$) centers in diamond could still manifest identical at Hz-precision level, corresponding to a ${10}^{-7}$-level relative precision, while the lattice strain can destroy the identity by tens of Hz. All parameters involved in the ${\mathrm{NV}}^{-}-{}^{14}\mathrm{N}$ Hamiltonian are determined by formulating six nuclear frequencies at 10-mHz-level precision and measuring them at Hz-level precision. The most precisely measured parameter, the ${}^{14}\mathrm{N}$ quadrupole coupling $P$, is given by $-4945754.9(8)\mathrm{Hz}$, whose precision is improved by nearly 4 orders of magnitude compared with previous measurements. We offer an approach for performing precision measurements in solids and deepening our understandings of NV centers as well as other solid-state defects. Besides, these high-precision results imply a potential application of a robust and integrated atomiclike clock based on ensemble NV centers.

Hot electrons generated by laser-plasma instabilities degrade the performance of laser-fusion implosions by preheating the DT fuel and reducing core compression. The hot-electron energy deposition in the DT fuel has been directly measured for the first time by comparing the hard x-ray signals between DT-layered and mass-equivalent ablator-only implosions. The electron energy deposition profile in the fuel is inferred through dedicated experiments using Cu-doped payloads of varying thickness. The measured preheat energy accurately explains the areal-density degradation observed in many OMEGA implosions. This technique can be used to assess the viability of the direct-drive approach to laser fusion with respect to the scaling of hot-electron preheat with laser energy.

We report observations of nanosecond nonuniform colloidal dynamics in a free flowing liquid jet using ultrafast x-ray speckle visibility spectroscopy. Utilizing a nanosecond double-bunch mode, the Linac Coherent Light Source free electron laser produced pairs of femtosecond coherent hard x-ray pulses. By exploring anisotropy in the visibility of summed speckle patterns which relates to the correlation functions, we evaluate not only the average particle flow rate in a colloidal nanoparticle jet, but also the nonuniform flow field within. The methodology presented here establishes the foundation for the study of nano- and atomic-scale inhomogeneous fluctuations in complex matter using x-ray free electron laser sources.

We demonstrate a new approach for fast preparation, manipulation, and collective readout of an atomic Rydberg-state qubit. By making use of Rydberg blockade inside a small atomic ensemble, we prepare a single qubit within $3\mu \mathrm{s}$ with a success probability of $F_p=0.93\pm 0.02$, rotate it, and read out its state in $6\mu \mathrm{s}$ with a single-shot fidelity of $F_d=0.92\pm 0.04$. The ensemble-assisted detection is ${10}^3$ times faster than imaging of a single atom with the same optical resolution, and enables fast repeated nondestructive measurement. We observe qubit coherence times of $15\mu \mathrm{s}$, much longer than the $\pi$ rotation time of 90 ns. Potential applications ranging from faster quantum information processing in atom arrays to efficient implementation of quantum error correction are discussed.

In this work, we combine quantum renormalization group approaches with deep artificial neural networks for the description of the real-time evolution in strongly disordered quantum matter. We find that this allows us to accurately compute the long-time coherent dynamics of large many-body localized systems in nonperturbative regimes including the effects of many-body resonances. Concretely, we use this approach to describe the spatiotemporal buildup of many-body localized spin-glass order in random Ising chains. We observe a fundamental difference to a noninteracting Anderson insulating Ising chain, where the order only develops over a finite spatial range. We further apply the approach to strongly disordered two-dimensional Ising models, highlighting that our method can be used also for the description of the real-time dynamics of nonergodic quantum matter in a general context.

We present a new method, exact in ${\alpha }^{\prime }$, to explicitly compute string tree-level amplitudes involving one massive state and any number of massless ones. This construction relies on the so-called twisted heterotic string, which admits only gauge multiplets, a gravitational multiplet, and a single massive supermultiplet in its spectrum. In this simplified model, we determine the moduli-space integrand of all amplitudes with one massive state using Berends-Giele currents of the gauge multiplet. These integrands are then straightforwardly mapped to gravitational amplitudes in the twisted heterotic string and to the corresponding massive amplitudes of the conventional type-I and type-II superstrings.

The bottom quark forward-backward asymmetry ($A_{\mathrm{FB}}^b$) data at LEP exhibits a long-standing discrepancy with the standard model prediction. We propose a novel method to probe the $Zb\overline{b}$ interactions through $gg\to Zh$ production at the LHC, which is sensitive to the axial-vector component of the $Zb\overline{b}$ couplings. The apparent degeneracy of the anomalous $Zb\overline{b}$ couplings implied by the LEP precision electroweak measurements seems to be resolved by the current 13 TeV LHC $Zh$ data, which is, however, dominated by the two data points with high transverse momentum of $Z$ boson whose central values are in conflict with the standard model prediction. We also show the potential of the HL-LHC to either verify or exclude the anomalous $Zb\overline{b}$ couplings observed at LEP through measuring the $Zh$ production rate at the HL-LHC, and this conclusion is not sensitive to the possible new physics contribution induced by top quark or Higgs boson anomalous couplings in the loop.

A search for charged leptons with large impact parameters using $139{\mathrm{fb}}^{-1}$ of $\sqrt{s}=13\mathrm{TeV}$ $pp$ collision data from the ATLAS detector at the LHC is presented, addressing a long-standing gap in coverage of possible new physics signatures. Results are consistent with the background prediction. This search provides unique sensitivity to long-lived scalar supersymmetric lepton partners (sleptons). For lifetimes of 0.1 ns, selectron, smuon, and stau masses up to 720, 680, and $340\mathrm{GeV}$, respectively, are excluded at 95% confidence level, drastically improving on the previous best limits from LEP.

We derive the collision term in the Boltzmann equation using the equation of motion for the Wigner function of massive spin-$1/2$ particles. To next-to-lowest order in $\hslash$, it contains a nonlocal contribution, which is responsible for the conversion of orbital into spin angular momentum. In a proper choice of pseudogauge, the antisymmetric part of the energy-momentum tensor arises solely from this nonlocal contribution. We show that the collision term vanishes in global equilibrium and that the spin potential is, then, equal to the thermal vorticity. In the nonrelativistic limit, the equations of motion for the energy-momentum and spin tensors reduce to the well-known form for hydrodynamics for micropolar fluids.

The Breit-Wheeler process which produces matter and antimatter from photon collisions is experimentally investigated through the observation of 6085 exclusive electron-positron pairs in ultraperipheral $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The measurements reveal a large fourth-order angular modulation of $\cos 4\mathrm{\Delta }\varphi =(16.8\pm 2.5)\%$ and smooth invariant mass distribution absent of vector mesons ($\varphi$, $\omega$, and $\rho$) at the experimental limit of $\le 0.2\%$ of the observed yields. The differential cross section as a function of $e^{+}{e}^{-}$ pair transverse momentum $P_{\perp }$ peaks at low value with $\sqrt{⟨P_{\perp }^2⟩}=38.1\pm 0.9\mathrm{MeV}$ and displays a significant centrality dependence. These features are consistent with QED calculations for the collision of linearly polarized photons quantized from the extremely strong electromagnetic fields generated by the highly charged Au nuclei at ultrarelativistic speed. The experimental results have implications for vacuum birefringence and for mapping the magnetic field which is important for emergent QCD phenomena.