Enhancing Dynamic Range of Sub-Standard-Quantum-Limit Measurements via Quantum Deamplification.

Balancing high sensitivity with a broad dynamic range is a fundamental challenge in measurement science, as improving one often compromises the other. While traditional quantum metrology has prioritized enhancing local sensitivity, a large dynamic range is crucial for applications such as atomic clocks, where extended phase interrogation times contribute to wider phase range. In this Letter, we introduce a novel quantum deamplification mechanism that extends dynamic range at a minimal cost of sensitivity.

Pseudospin Transverse Localization of Light in an Optical Disordered Spin-Glass Phase.

Localization phenomena during transport are typically associated with disordered scalar potentials. Here, we predict a universal pseudospin localization phenomenon driven by a disordered vectorial potential and experimentally observe its onset in an optical analog of a classical disordered spin-glass magnetic phase. In our system, disorder in the second-order nonlinear coupling of a nonlinear photonic crystal causes the idler-signal light beam, representing the pseudospin current, to approach localization in the transverse plane.

Site-Selective Cavity Readout and Classical Error Correction of a 5-Bit Atomic Register.

Optical cavities can provide fast and nondestructive readout of individual atomic qubits; however, scaling up to many qubits remains a challenge. Using locally addressed excited-state Stark shifts to tune atoms out of resonance, we realize site-selective hyperfine-state cavity readout across a ten-site array. The state discrimination fidelity is 0.

Near-field photon entanglement in total angular momentum.

Photons can carry angular momentum, which is conventionally attributed to two constituents-spin angular momentum (SAM), which is an intrinsic property related to the polarization, and orbital angular momentum (OAM), which is related to the photon spatial distribution. In paraxial optics, these two forms of angular momentum are separable, such that entanglement can be induced between the SAM and the OAM of a single photon or of different photons in a multi-photon state. In nanophotonic systems, however, the SAM and the OAM of a photon are inseparable, so only the total angular momentum (TAM) serves as a good quantum number.

Four-dimensional conserved topological charge vectors in plasmonic quasicrystals.

According to Noether's theorem, symmetries in a physical system are intertwined with conserved quantities. These symmetries often determine the system topology, which is made ever more complex with increased dimensionality. Quasicrystals have neither translational nor global rotational symmetry, yet they intrinsically inhabit a higher-dimensional space in which symmetry resurfaces.

Dynamic control and manipulation of near-fields using direct feedback.

Shaping and controlling electromagnetic fields at the nanoscale is vital for advancing efficient and compact devices used in optical communications, sensing and metrology, as well as for the exploration of fundamental properties of light-matter interaction and optical nonlinearity. Real-time feedback for active control over light can provide a significant advantage in these endeavors, compensating for ever-changing experimental conditions and inherent or accumulated device flaws. Scanning nearfield microscopy, being slow in essence, cannot provide such a real-time feedback that was thus far possible only by scattering-based microscopy.

Entanglement on an optical atomic-clock transition.

State-of-the-art atomic clocks are based on the precise detection of the energy difference between two atomic levels, which is measured in terms of the quantum phase accumulated over a given time interval. The stability of optical-lattice clocks (OLCs) is limited both by the interrupted interrogation of the atomic system by the local-oscillator laser (Dick noise) and by the standard quantum limit (SQL) that arises from the quantum noise associated with discrete measurement outcomes. Although schemes for removing the Dick noise have been recently proposed and implemented, performance beyond the SQL by engineering quantum correlations (entanglement) between atoms has been demonstrated only in proof-of-principle experiments with microwave clocks of limited stability.

Near-Unitary Spin Squeezing in ^{171}Yb.

Spin squeezing can improve atomic precision measurements beyond the standard quantum limit (SQL), and unitary spin squeezing is essential for improving atomic clocks. We report substantial and nearly unitary spin squeezing in ^{171}Yb, an optical lattice clock atom. The collective nuclear spin of ∼10^{3} atoms is squeezed by cavity feedback, using light detuned from the system's resonances to attain unitarity.

Direct Laser Cooling to Bose-Einstein Condensation in a Dipole Trap.

We present a method for producing three-dimensional Bose-Einstein condensates using only laser cooling. The phase transition to condensation is crossed with 2.5×10^{4} ^{87}Rb atoms at a temperature of T_{c}=0.

Observation of Aubry-type transition in finite atom chains via friction.

The highly nonlinear many-body physics of a chain of mutually interacting atoms in contact with a periodic substrate gives rise to complex static and dynamical phenomena, such as structural phase transitions and friction. In the limit of an infinite chain incommensurate with the substrate, Aubry predicted a transition with increasing substrate potential, from the chain's intrinsic arrangement free to slide on the substrate, to a pinned arrangement favouring the substrate pattern. So far, the Aubry transition has not been observed.

Note: Fast compact laser shutter using a direct current motor and three-dimensional printing.

We present a mechanical laser shutter design that utilizes a direct current electric motor to rotate a blade which blocks and unblocks a light beam. The blade and the main body of the shutter are modeled with computer aided design (CAD) and are produced by 3D printing. Rubber flaps are used to limit the blade's range of motion, reducing vibrations and preventing undesirable blade oscillations.

Quantum-gas microscope for fermionic atoms.

We realize a quantum-gas microscope for fermionic ^{40}K atoms trapped in an optical lattice, which allows one to probe strongly correlated fermions at the single-atom level. We combine 3D Raman sideband cooling with high-resolution optics to simultaneously cool and image individual atoms with single-lattice-site resolution at a detection fidelity above 95%. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states.

Scale-specific multifractal medical image analysis.

Fractal geometry has been applied widely in the analysis of medical images to characterize the irregular complex tissue structures that do not lend themselves to straightforward analysis with traditional Euclidean geometry. In this study, we treat the nonfractal behaviour of medical images over large-scale ranges by considering their box-counting fractal dimension as a scale-dependent parameter rather than a single number. We describe this approach in the context of the more generalized Rényi entropy, in which we can also compute the information and correlation dimensions of images.

Proposal to observe the nonlocality of Bohmian trajectories with entangled photons.

Bohmian mechanics reproduces all statistical predictions of quantum mechanics, which ensures that entanglement cannot be used for superluminal signaling. However, individual Bohmian particles can experience superluminal influences. We propose to illustrate this point using a double double-slit setup with path-entangled photons.

Long-external-cavity distributed Bragg reflector laser with subkilohertz intrinsic linewidth.

We report on a simple, compact, and robust 780 nm distributed Bragg reflector laser with subkilohertz intrinsic linewidth. An external cavity with optical path length of 3.6 m, implemented with an optical fiber, reduces the laser frequency noise by several orders of magnitude.

Orientation-dependent entanglement lifetime in a squeezed atomic clock.

We study experimentally the application of a class of entangled states, squeezed spin states, to the improvement of atomic-clock precision. In the presence of anisotropic noise, the entanglement lifetime is strongly dependent on squeezing orientation. We measure the Allan deviation spectrum of a clock operated with a phase-squeezed input state.

Implementation of cavity squeezing of a collective atomic spin.

We squeeze unconditionally the collective spin of a dilute ensemble of laser-cooled 87Rb atoms using their interaction with a driven optical resonator. The shape and size of the resulting spin uncertainty region are well described by a simple analytical model [M. H.

Observation of strong quantum depletion in a gaseous Bose-Einstein condensate.

We studied quantum depletion in a gaseous Bose-Einstein condensate. An optical lattice enhanced the atomic interactions and modified the dispersion relation resulting in strong quantum depletion. The depleted fraction was directly observed as a diffuse background in the time-of-flight images.