In the presence of Rashba spin-orbit coupling, a magnetic field can drive a proximitized nanowire into a topological superconducting phase [R. M. Lutchyn, J. D. Sau, and S. Das Sarma, Phys. Rev. Lett. 105, 077001 (2010). and Y. Oreg, G. Refael, and F. von Oppen, Phys. Rev. Lett. 105, 177002 (2010).]. We study the transport properties of such nanowires in the Coulomb blockade regime. The associated with topological superconductivity Majorana modes significantly modify transport and lead to single-electron coherent transmission through the nanowire—a nonlocal signature of topological superconductivity. In this Letter, we focus on the case of strong hybridization of the Majorana modes with normal leads. The induced by hybridization broadening of the Majorana zero-energy states competes with the charging energy, leading to a considerable modification of the Coulomb blockade in a nanowire contacted by two normal leads. We evaluate the two-terminal conductance as a function of the gate voltage, junctions transmission coefficients, and the geometric capacitance of and the induced superconducting gap in the nanowire.

Current theories of superfluidity are based on the idea of a coherent quantum state with topologically protected quantized circulation. When this topological protection is absent, as in the case of ${}^3\mathrm{He}\text{−}A$, the coherent quantum state no longer supports persistent superflow. Here, we argue that the loss of topological protection in a superconductor gives rise to an insulating ground state. We specifically introduce the concept of a Skyrme insulator to describe the coherent dielectric state that results from the topological failure of superflow carried by a complex-vector order parameter. We apply this idea to the case of ${\mathrm{SmB}}_6$, arguing that the observation of a diamagnetic Fermi surface within an insulating bulk can be understood as a realization of this state. Our theory enables us to understand the linear specific heat of ${\mathrm{SmB}}_6$ in terms of a neutral Majorana Fermi sea and leads us to predict that in low fields of order a Gauss, ${\mathrm{SmB}}_6$ will develop a Meissner effect.

The dielectric permittivity and properties of electrically active lattice resonances in nanotwinned ${\mathrm{BiFeO}}_3$ crystals have been studied theoretically using an earlier established interatomic potential. The results suggest that an array of 71° domain walls with about 2–5 nm spacing enhances the static permittivity of ${\mathrm{BiFeO}}_3$ by more than an order of magnitude. This enhancement is associated with an electrically active excitation, corresponding to a collective vibration of pinned domain walls at a remarkably high frequency of about 0.3 THz.

This Letter demonstrates control over multiphoton absorption processes in driven two-level systems, which include, for example, superconducting qubits or laser-irradiated graphene, through spectral shaping of the driving pulse. Starting from calculations based on Floquet theory, we use differential evolution, a general purpose optimization algorithm, to find the Fourier coefficients of the driving function that suppress a given multiphoton resonance in the strong field regime. We show that the suppression of the transition probability is due to the coherent superposition of high-order Fourier harmonics which closes the dynamical gap between the Floquet states of the two-level system.

Subradiant excitations, originally predicted by Dicke, have posed a long-standing challenge in physics owing to their weak radiative coupling to environment. Here we engineer massive coherently driven classical subradiance in planar metamaterial arrays as a spatially extended eigenmode comprising over 1000 metamolecules. By comparing the near- and far-field response in large-scale numerical simulations with those in experimental observations we identify strong evidence for classically correlated multimetamolecule subradiant states that dominate the total excitation energy. We show that similar spatially extended many-body subradiance can also exist in plasmonic metamaterial arrays at optical frequencies.

We report on a class of quantum spin Hall insulators (QSHIs) in strained-layer $\mathrm{InAs}/\mathrm{GaInSb}$ quantum wells, in which the bulk gaps are enhanced up to fivefold as compared to the binary $\mathrm{InAs}/\mathrm{GaSb}$ QSHI. Remarkably, with consequently increasing edge velocity, the edge conductance at zero and applied magnetic fields manifests time reversal symmetry-protected properties consistent with the $Z_2$ topological insulator. The $\mathrm{InAs}/\mathrm{GaInSb}$ bilayers offer a much sought-after platform for future studies and applications of the QSHI.

Recent experiments have revealed that beyond-mean-field corrections are much more relevant in weakly interacting dipolar condensates than in their nondipolar counterparts. We show that in quasi-one-dimensional geometries quantum corrections in dipolar and nondipolar condensates are strikingly different due to the peculiar momentum dependence of the dipolar interactions. The energy correction of the condensate presents not only a modified density dependence, but it may even change from attractive to repulsive at a critical density due to the surprising role played by the transversal directions. The anomalous quantum correction translates into a strongly modified physics for quantum-stabilized droplets and dipolar solitons. Moreover, and for similar reasons, quantum corrections of three-body correlations, and hence of three-body losses, are strongly modified by the dipolar interactions. This intriguing physics can be readily probed in current experiments with magnetic atoms.

We propose a method for increasing the purity of interacting quantum systems that takes advantage of correlations present due to the internal interaction. In particular, when this interaction is sufficiently strong, we show that by using the system’s quantum correlations one can achieve cooling beyond established limits of previous conventional algorithmic cooling proposals which assume no interaction.

To date, blind quantum computing demonstrations require clients to have weak quantum devices. Here we implement a proof-of-principle experiment for completely classical clients. Via classically interacting with two quantum servers that share entanglement, the client accomplishes the task of having the number 15 factorized by servers who are denied information about the computation itself. This concealment is accompanied by a verification protocol that tests servers’ honesty and correctness. Our demonstration shows the feasibility of completely classical clients and thus is a key milestone towards secure cloud quantum computing.

We develop a perturbation theory of quantum (and classical) master equations with slowly varying parameters, applicable to systems which are externally controlled on a time scale much longer than their characteristic relaxation time. We apply this technique to the analysis of finite-time isothermal processes in which, differently from quasistatic transformations, the state of the system is not able to continuously relax to the equilibrium ensemble. Our approach allows one to formally evaluate perturbations up to arbitrary order to the work and heat exchange associated with an arbitrary process. Within first order in the perturbation expansion, we identify a general formula for the efficiency at maximum power of a finite-time Carnot engine. We also clarify under which assumptions and in which limit one can recover previous phenomenological results as, for example, the Curzon-Ahlborn efficiency.

The quantum Cramér-Rao bound (QCRB) sets a fundamental limit for the measurement of classical signals with detectors operating in the quantum regime. Using linear-response theory and the Heisenberg uncertainty relation, we derive a general condition for achieving such a fundamental limit. When applied to classical displacement measurements with a test mass, this condition leads to an explicit connection between the QCRB and the standard quantum limit that arises from a tradeoff between the measurement imprecision and quantum backaction; the QCRB can be viewed as an outcome of a quantum nondemolition measurement with the backaction evaded. Additionally, we show that the test mass is more a resource for improving measurement sensitivity than a victim of the quantum backaction, which suggests a new approach to enhancing the sensitivity of a broad class of sensors. We illustrate these points with laser interferometric gravitational-wave detectors.

We report the results of a $\beta$-decay study of fission products ${}^{86}\mathrm{Br}$, ${}^{89}\mathrm{Kr}$, ${}^{89}\mathrm{Rb}$, ${}^{90gs}\mathrm{Rb}$, ${}^{90m}\mathrm{Rb}$, ${}^{90}\mathrm{Kr}$, ${}^{92}\mathrm{Rb}$, ${}^{139}\mathrm{Xe}$, and ${}^{142}\mathrm{Cs}$ performed with the Modular Total Absorption Spectrometer (MTAS) and on-line mass-separated ion beams. These radioactivities were assessed by the Nuclear Energy Agency as having high priority for decay heat analysis during a nuclear fuel cycle. We observe a substantial increase in $\beta$ feeding to high excited states in all daughter isotopes in comparison to earlier data. This increases the average $\gamma$-ray energy emitted by the decay of fission fragments during the first 10 000 s after fission of ${}^{235}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$ by approximately 2% and 1%, respectively, improving agreement between results of calculations and direct observations. New MTAS results reduce the reference reactor ${\overline{\nu }}_e$ flux used to analyze reactor ${\overline{\nu }}_e$ interaction with detector matter. The reduction determined by the ab initio method for the four nuclear fuel components, ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, ${}^{239}\mathrm{Pu}$, and ${}^{241}\mathrm{Pu}$, amounts to 0.976, 0.986, 0.983, and 0.984, respectively.

The stereodynamics of the $\mathrm{Ne}({}^3{\mathrm{P}}_2)+\mathrm{Ar}$ Penning and associative ionization reactions have been studied using a crossed molecular beam apparatus. The experiment uses a curved magnetic hexapole to polarize the $\mathrm{Ne}({}^3{\mathrm{P}}_2)$, which is then oriented with a shaped magnetic field in the region where it intersects with a beam of $\mathrm{Ar}({}^1\mathrm{S})$. The ratios of Penning to associative ionization were recorded over a range of collision energies from 320 to $500{\mathrm{cm}}^{-1}$ and the data were used to obtain $\mathrm{\Omega }$ state dependent reactivities for the two reaction channels. These reactivities were found to compare favorably to those predicted in the theoretical work of Brumer et al.

Slow atoms in Rydberg states can exhibit specular reflection from a cylindrical surface upon which an azimuthally periodic potential is imposed. We have constructed a concave mirror of this type, in the shape of a truncated oblate ellipsoid of revolution, which has a focal length of $(1.50\pm 0.01)\mathrm{m}$ measured optically. When placed near the center of a long vacuum pipe, this structure brings a beam of $n=32$ positronium (Ps) atoms to a focus on a position sensitive detector at a distance of ($6.03\pm 0.03$) m from the Ps source. The intensity at the focus implies an overall reflection efficiency of $\sim 30\%$. The focal spot diameter $(32\pm 1)\mathrm{mm}$ full width at half maximum is independent of the atoms’ flight times from 20 to $60\mu \mathrm{s}$, thus indicating that the mirror is achromatic to a good approximation. Mirrors based on this principle would be of use in a variety of experiments, allowing for improved collection efficiency and tailored transport or imaging of beams of slow Rydberg atoms and molecules.

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

The acceleration of ions from ultrathin (10–100 nm) carbon foils has been investigated using intense ($\sim 6\times 10^{20}\mathrm{W}{\mathrm{cm}}^{-2}$) ultrashort (45 fs) laser pulses, highlighting a strong dependence of the ion beam parameters on the laser polarization, with circularly polarized (CP) pulses producing the highest energies for both protons and carbons ($25-30\mathrm{MeV}/\mathrm{nucleon}$); in particular, carbon ion energies obtained employing CP pulses were significantly higher ($\sim 2.5$ times) than for irradiations employing linearly polarized pulses. Particle-in-cell simulations indicate that radiation pressure acceleration becomes the dominant mechanism for the thinnest targets and CP pulses.

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.