Quantum information theory is plagued by the problem of regularizations, which require the evaluation of formidable asymptotic quantities. This makes it computationally intractable to gain a precise quantitative understanding of the ultimate efficiency of key operational tasks such as entanglement manipulation. Here, we consider the problem of computing the asymptotic entanglement cost of preparing noisy quantum states under quantum operations with positive partial transpose (PPT). By means of an analytical example, a previously claimed solution to this problem is shown to be incorrect. Building on a previous characterization of the PPT entanglement cost in terms of a regularized formula, we construct instead a hierarchy of semidefinite programs that bypasses the issue of regularization altogether, and converges to the true asymptotic value of the entanglement cost. Our main result establishes that this convergence happens exponentially fast, thus yielding an efficient algorithm that approximates the cost up to an additive error $ϵ$ in time $\mathrm{poly}(D,\log (1/ϵ))$, where $D$ is the underlying Hilbert space dimension. To our knowledge, this is the first time that an asymptotic entanglement measure is shown to be efficiently computable despite no closed-form formula being available.

We experimentally study the transient dynamics of a dissipative superconducting qubit under periodic drive toward its nonequilibrium steady states. The corresponding stroboscopic evolution, given by the qubit states at times equal to integer multiples of the drive period, is determined by a (generically non-Hermitian) Floquet Liouvillian. The drive period controls both the transients across its non-Hermitian degeneracies and the resulting nonequilibrium steady states. These steady states can exhibit higher purity compared to those achieved with a constant drive. We further study the dependence of the steady states on the direction of parameter variation and relate these findings to the recent studies of dynamically encircling exceptional points. Our Letter provides a new approach to control non-Hermiticity in dissipative quantum systems and presents a new paradigm in quantum state preparation and stabilization.

We propose a Clifford noise reduction (CliNR) scheme that provides a reduction of the logical error rate of Clifford circuit with lower overhead than error correction and without the exponential sampling overhead of error mitigation. CliNR implements Clifford circuits by splitting them into subcircuits that are performed using gate teleportation. A few random stabilizer measurements are used to detect errors in the resources states consumed by the gate teleportation. This can be seen as a teleported version of the coherent parity-check scheme [1–3], with offline fault-detection making it scalable. We prove that CliNR achieves a vanishing logical error rate for families of $n$-qubit Clifford circuits with size $s$ such that $ns{p}^2$ goes to 0, where $p$ is the physical error rate, meaning that it reaches the regime $ns=o(1/p^2)$, whereas the direct implementation is limited to $s=o(1/p)$. Moreover, CliNR uses only $3n+1$ qubits, $2s+o(s)$ gates and has zero rejection rate. This small overhead makes it more practical than quantum error correction in the near term and our numerical simulations show that CliNR provides a reduction of the logical error rate in relevant noise regimes.

We introduce semidefinite programming hierarchies for benchmarking relevant entanglement properties in the high-dimensional steering scenario. Firstly, we provide a general method for detecting the entanglement dimensionality through certification of the Schmidt number. Its key feature is that the computational cost is independent of the Schmidt number under consideration. Secondly, we provide a method to estimate the fidelity of the source with any maximally entangled state. Using only basic computational means, we demonstrate the usefulness of these methods, which can be directly used to analyze experiments on high-dimensional systems.

Quantum turbulence is a far-from-equilibrium process characterized by high nonlinearity. Holographic duality provides a systematic framework for simulating the decaying ($3+1$)-dimensional quantum turbulence by numerically solving the dual Abelian-Higgs theory in a ($4+1$)-dimensional black hole background. We reveal that different types of decay behavior of the total vortex line density $L$ emerge depending on the initial vortex line density, ranging from $L\sim t^{-1.5}$ to $L\sim t^{-1}$, similar to the experimental observation of ${}^3\mathrm{He}$ in Bradley et al. [Phys. Rev. Lett. 96, 035301 (2006)], and of ${}^4\mathrm{He}$ in Stalp et al. [Phys. Rev. Lett. 82, 4831 (1999)] and in Walmsley and Golov [Phys. Rev. Lett. 118, 134501 (2017)]. Furthermore, by measuring the energy flux at the black hole horizon, we determine that the energy dissipation rate $dE/dt$ is proportional to the square of the total vortex line density, consistent with the vortex line decay equation proposed by W. F. Vinen and also the experimental measurement in Nat. Phys. 7, 473 (2011).

We accomplish for the first time the next-to-leading-order computation of the weak annihilation contribution to the electroweak penguin decays $B\to \{K,\pi \}{\ell }^{+}{\ell }^{-}$, which is an essential missing piece of the complete QCD correction to the matrix elements of hadronic operators in the weak effective Hamiltonian. Both the hard functions and the jet functions in the perturbative factorization formulas from the short-distance fluctuations at the two distinct scales $m_b$ and $\sqrt{m_b\mathrm{\Lambda }}$ are determined at $\mathcal{O}({\alpha }_s)$. We then demonstrate that the one-loop weak annihilation correction can bring about the noticeable impacts on theory predictions for the $CP$ asymmetries and the isospin asymmetry in the $B\to \pi {\ell }^{+}{\ell }^{-}$ decays.

Remarkably large double electron capture cross sections, on the scale of ${10}^{-15}{\mathrm{cm}}^2$, are observed in low-energy ($<50\mathrm{eV}/\mathrm{u}$) collisions between ${\mathrm{Sn}}^{3+}$ and ${\mathrm{H}}_2$. Given that the reaction is energetically highly unfavorable, one would expect negligibly small cross sections. Through the propagation of vibrational wave packets on coupled multiple potential energy surfaces, a novel charge transfer mechanism, driven in tandem by ion motion and molecular vibration, is revealed, offering insights into the unusual energy dependence of the measured cross sections.

There is renewed interest in studies of muonic atoms, which may provide detailed information on nuclear structure. A major limiting factor in the interpretation of measurements is the nuclear polarization contribution. We propose a method to determine this contribution to the hyperfine structure in muonic atoms from a combination of theory and experiment for hydrogenlike ions and muonic atoms. Applying the method to ${}^{203,205}\mathrm{Tl}$ and ${}^{209}\mathrm{Bi}$, for which there are H-like ion and muonic atom hyperfine experimental data, we find that the nuclear polarization contribution for these systems is small and place a limit on its size of less than 10% the total hyperfine splitting. We have also performed direct calculations of the nuclear polarization contribution using a semianalytical model, which indicate that it may be as much as two orders of magnitude smaller. Therefore, the nuclear polarization correction to the hyperfine structure of muonic atoms does not represent a limiting factor for next-generation experiments.

It has been shown by Fano [1] that photoionization of a cesium atom by a laser pulse tuned to the vicinity of a Cooper minimum generates spin-polarized electrons. Here we show that while photoionization of rare gases does not provide large spin polarization in the vicinity of the Cooper minimum, the Fano resonances yield much higher overall spin polarization $(\ge 40\%)$. The spin polarization increases in angle-resolved photoelectron spectra, and reaches 100% when measured in coincidence with the photoion. A common feature of both Cooper minima and Fano resonances, is the large variation of the photoinization cross section over photon energy, which proves to be vital for efficient generation of spin-polarized electrons. We provide a general framework for achieving spin polarization in photoionization irrespective of the ionization regime.

We prove that it is impossible to distinguish two spatially coinciding fluorescent molecules from a single rotating molecule using polarization-sensitive imaging, even if one modulates the polarization of the illumination or the detection dipole-spread function (DSF). If the target is known to be a dipole pair, existing imaging methods perform poorly for measuring their angular separation. We propose simultaneously modulating the excitation polarization and DSF, which demonstrates robust discrimination between dipole pairs versus single molecules. Our method improves the precision of measuring centroid orientation by 50% and angular separation by two- to four-fold over existing techniques.

Lift force of viscous origin is widespread across disciplines, from mechanics to biology. Here, we present the first direct measurement of the lift force acting on a particle moving in a viscous fluid along the liquid interface that separates two liquids. The force arises from the coupling between the viscous flow induced by the particle motion and the capillary deformation of the interface. The measurements show that the lift force increases as the distance between the sphere and the interface decreases, reaching saturation at small distances. The experimental results are in good agreement with the model and numerical calculation developed within the framework of the soft lubrication theory.

We report the first experimental detection of a zero-frequency fluctuation that is pumped by an Alfvén mode in a magnetically confined plasma. Core-localized Alfvén modes of frequency inside the toroidicity-induced gap (and its harmonics) exhibit three-wave coupling interactions with a zero-frequency fluctuation. The observation of the zero-frequency fluctuation is consistent with theoretical and numerical predictions of zonal modes pumped by Alfvén modes, and is correlated with an increase in the deep core ion temperature, temperature gradient, confinement factor $H_{89,P}$, and a reduction in the main ion heat diffusivity. Despite the energetic particle transport induced by the Alfvén eigenmodes, the generation of a zero-frequency fluctuation that can suppress the turbulence leads to an overall improvement of confinement.

We previously reported the discovery of a two-dimensional ${}^4\mathrm{He}$ supersolid; a state with intertwined density wave and superfluid order, observed in the second layer of ${}^4\mathrm{He}$ adsorbed on graphite. In this Letter we provide direct evidence for the density wave order, obtained by doping the layer with a small concentration of ${}^3\mathrm{He}$ atoms (impuritons). The heat capacity, magnetization and NMR relaxation times of the ${}^3\mathrm{He}$ were measured over a wide temperature range from $200\mathrm{\mu }\mathrm{K}$ to 500 mK. They provide evidence for changes in the ground state in the second layer film as the amount of ${}^4\mathrm{He}$ is increased at various fixed ${}^3\mathrm{He}$ doses. Clear evidence is obtained for a solid second layer film, matching the regime of superfluid response previously observed in pure ${}^4\mathrm{He}$ films.

We report on a double moiré system consisting of four graphene layers, where the top and bottom pairs form small-twist-angle bilayer graphene, and the middle interface has a large rotational mismatch. This system shows clear signatures of two sets of spatially separated flat bands associated with the top and bottom twisted bilayer graphene subsystems, each independently tunable. Thermodynamic analysis reveals weak correlations between bilayers that allow the chemical potential to be measured as a function of carrier density for each constituent TBG. We find that correlated insulating states at integer number of electrons per moiré unit cell are most robust near magic angle, whereas gapped states at neutrality are more robust at larger twist angles.

We demonstrate the formation of ferroelectric domain-wall polarons in a minimal two-dimensional lattice model of electrons interacting with rotating dipoles. Along the domain wall, the rotors polarize in opposite directions, causing the electron to localize along a particular lattice direction. The rotor-electron coupling is identified as the origin of a structural instability in the crystal that leads to the domain-wall formation via a symmetry-breaking process. Our results provide the first theoretical description of ferroelectric polarons, as discussed in the context of soft semiconductors.

The low-energy dynamics of two-dimensional topological matter hinges on its one-dimensional edge modes. Tunneling between fractional quantum Hall edge modes facilitates the study of anyonic statistics: it induces time-domain braiding that dominates signals from diluted anyon beams. We develop a framework for characterizing one-dimensional out-of-equilibrium anyonic states and define their effective potential and temperature, both arising from anyonic braiding, as well as the landscape of their excitations. Unlike fermions, the effective anyon potential depends on the type of the tunneling quasiparticles; nonequilibrium anyonic states are underlain by power-law energy distributions. This allows “hot” anyons to tunnel above the chemical potential of the source, which we capture by a measurable universal witness function. Our analysis raises the prospect of generalizing the kinetic approach to compressible anyonic matter in higher dimensions.

We unveil multifaceted effects of spin-charge couplings on the high-harmonic generation (HHG) in Mott insulators by analyzing the two-leg ladder Hubbard model, where spin dynamics activated by the interchain hopping $t_y$ drastically modifies the HHG features. When the two chains are decoupled ($t_y=0$), HHG originates from the dynamics of coherent doublon-holon pairs because of spin-charge separation. With increasing $t_y$, the doublon-holon pairs lose their coherence due to their interchain hopping and resultant nonlocal spin strings. Furthermore, the HHG signal from spin polarons—charges dressed by spin clouds—leads to an additional plateau in the HHG spectrum. For large $t_y$, we identify unconventional HHG processes involving three elementary excitations—two polarons and one magnon. Our study is an essential step toward a microscopic understanding of nontrivial many-body effects on HHG in correlated materials beyond conventional semiconductors.