Quantum entanglement provides a novel way to test short-distance quantum physics in a nonrelativistic regime. We provide entanglement-based protocols to potentially test the magnetically induced dipole-dipole interaction and the Casimir-Polder potential between the two nanocrystals kept in a Schrödinger cat state. Our scheme is based on the Stern-Gerlach (SG) apparatus, where we can witness the entanglement mediated by these interactions for the nanocrystal mass $m\sim {10}^{-19}$ kg with a spatial superposition size of order $0.1\mu \text{m}$ in a trap relying on diamagnetic levitation. We show that it is possible to close the SG interferometer in position and momentum with a modest gradient in the magnetic field.

We study the thermal behavior of correlations in a one-dimensional Bose gas with tunable interaction strength, crossing from weakly repulsive to the Tonks-Girardeau regime. A reference temperature in this system is that of the hole anomaly, observed as a peak in the specific heat and a maximum in the chemical potential. We find that at large momenta $k$ and temperature above the anomaly threshold, the tail $\mathcal{C}/k^4$ of the momentum distribution (proportional to the Tan contact $\mathcal{C}$) is screened by the $1/{\left|k\right|}^3$ term due to a dramatic thermal increase of the internal energy emerging from the thermal occupation of spectral excitation states. The same fading is consistently revealed in the behavior at short distances $x$ of the one-body density matrix (OBDM) where the ${\left|x\right|}^3$ dependence disappears for temperatures above the anomaly. We obtain a general analytic tail for the momentum distribution and a minimum $k$ fixing its validity range, both calculated with exact Bethe-Ansatz method and valid in all interaction and thermal regimes, crossing from the quantum to the classical gas limit. Our predictions are confirmed by comparison with ab initio path-integral Monte Carlo calculations for the momentum distribution and the OBDM exploring a wide range of interaction strength and temperature. Our results unveil a connection between excitations and correlations. We expect them to be of interest to any cold atomic, nuclear, solid-state, electronic, and spin system exhibiting an anomaly or a thermal second-order phase transition.

The Brewster effect has a number of applications in antireflection coatings, spectroscopy, and polarization optics, but its tunability is still of high demand. In this Letter, we discover a method of Brewster angle control with two-dimensional conducting layers. Namely, we analyze the angular shift of Brewster's angle depending on the surface conductivity of a two-dimensional layer. First, we derive the analytical model with exact conductivity-dependent solution. Then, we investigate the Brewster angle shift in the cases of monolayer graphene and plasmonic metasurface. Finally, we support our analytical results by the full-wave numerical simulations. The results obtained may find a plethora of applications in flat optical and planar photonic devices.

We investigate the simultaneous presence of several photons in disordered three-dimensional cold atom clouds, beyond the idealized condition of a single photon for Anderson localization. We find that the presence of these multiple excitations does not affect substantially the abnormal intensity fluctuations which characterize the Anderson localization transition, provided that the radiated light is frequency filtered. Indeed, long-lived modes, and particularly the localized ones, are strongly saturated even for a weak pump, leading to a large increase of the inelastic scattering and to reduced fluctuations in the total radiation. Yet the atomic coherences and the resulting elastic scattering remain a proper witness of the Anderson localization transition. Thus, frequency filtering appears as an efficient tool to discriminate single-excitation phenomena from many-body ones, and one can expect that the fluorescence spectrum will in turn allow us to investigate many-body localization.

As a phenomenon encompassing measurement incompatibility and Bell nonlocality, quantum contextuality is not only central to our understanding of quantum mechanics, but also an essential resource in many quantum information processing tasks. The dimension-dependent feature of quantum contextuality is known ever since its discovery, but there is still a lack of systematic methods for characterizing this fundamental feature. In this work, we propose a systematic and reliable method for certifying the high-dimensional advantages of quantum contextuality. In theory, our work gives a complete characterization of the dimension-constrained quantum contextual behavior, and particularly its nonconvex structure is revealed. In application, our method can be used for dimensionality certification of quantum information processing systems, and also for concentrating the quantum contextual behavior into lower-dimensional systems.

We present a study on the development of rotating turbulence in Bose-Einstein condensates with a dissipative Gross-Pitaevskii model. Turbulence is generated by driving the lattice of quantized vortices in a harmonic potential with a random forcing potential. As the turbulence progresses, the initial alignment of vortices undergoes slight disruptions, thereby increasing the high-wave-number components of the kinetic energy. In the turbulent state, the distribution of incompressible kinetic energy exhibits milder anisotropy than that in the initial lattice state and demonstrates a scaling behavior of $k_z^{-2.5}$ in the direction parallel to the rotation axis. In contrast, the compressible kinetic energy exhibits an isotropic scaling behavior at high wave numbers.

We show that the delocalization-localization transition in quantum many-body (QMB) systems are a compelling quantum resource for achieving quantum-enhanced sensitivity in parameter estimation. We exploit the vulnerability of a near-transition QMB state against the parameter shift for devising efficient sensing tools. In this realm the main focus of this work is to identify, propose, and analyze experimentally relevant quantum observables for precision measurement. Taking a QMB system as a Fermi lattice under quasiperiodic modulation that supports an energy-independent delocalization-localization transition, we suggest operator-based adiabatic and dynamical quantum sensors endowed with considerable quantum advantages. In particular, we analyze single-particle systems and the system at half-filling. While the quantum Fisher information saturates the Heisenberg limit, we demonstrate the experimentally relevant suitable observables with a spotlight on the charge-density-wave operator. Demonstrating their efficacy, these observables emerge as promising candidates for experimentally exploiting quantum advantages, showcasing superior performance compared to the standard quantum limit in terms of system-size scaling. Taking our exploration further into the dynamical realm, we discuss observables that yield super-extensive generic scaling in measurement precision. The comprehensive nature of our study not only sheds light on the intricacies of the delocalization-localization transition, but also offers practical insights for the development of quantum sensors and their potential applications.

The phenomenon of quantum entanglement underlies several important protocols that enable emerging quantum technologies. Entangled states, however, are extremely delicate and often get perturbed by tiny fluctuations in their external environment. Certification of entanglement is therefore immensely crucial for the successful implementation of protocols involving this resource. In this Letter, we propose a set of entanglement criteria for multiqubit systems that can be easily verified by measuring certain thermodynamic quantities. In particular, the criteria depend on the difference in optimal global and local works extractable from an isolated quantum system under global and local interactions, respectively. As a proof of principle, we demonstrate the proposed scheme on nuclear spin registers of up to 10 qubits using the nuclear magnetic resonance architecture. We prepare a noisy Bell diagonal state and noisy Greenberger-Horne-Zeilinger class of states in star-topology systems and certify their entanglement through our thermodynamic criteria. Along the same line, we also propose an entanglement certification scheme in many-body systems when only partial or even no knowledge about the state is available.

We present an efficient approach for preparing ground states in the context of strongly interacting local quantum field theories on quantum computers. The approach produces the vacuum state in a time proportional to the square root of the volume, which is a square-root improvement in speed compared to traditional approaches. The approach exploits a method for traversing the path in parameter space in which the resources scale linearly with a path length suitably defined in parameter space. Errors due to practical limitations are controlled and do not exhibit secular growth along the path. The final accuracy can be arbitrarily improved with an additive cost, which is independent of the volume and grows slower than logarithmically with the overlap between the state produced and the exact ground state. We expect that the method could potentially hold practical value not only within the realm of quantum field theories but also in addressing other challenges involving long path lengths.

We propose a highly feasible technique with no experimental overhead to rapidly cool the in-plane degrees of freedom of large two-dimensional ion crystals in Penning traps. Through simulations, we demonstrate that our approach enables the in-plane modes to cool down to a temperature of around 1 mK in less than 10 ms. Our technique relies on near-resonant coupling of the poorly cooled in-plane motions and the efficiently cooled out-of-plane motions, and is achieved without introducing additional potentials. The rapid cooling enabled by our approach is in contrast to typical operating conditions, where our simulations of the laser cooling dynamics suggest that the ion crystal's in-plane motion cools very slowly on a timescale of several hundreds of milliseconds, a rate likely slower than experimental heating rates. Our work sets the stage for sub-Doppler laser cooling of the planar motion, and more robust and versatile quantum simulation and quantum sensing experiments with two-dimensional crystals in Penning traps.

We study the mechanism for realizing the non-Hermitian skin effect (NHSE) via dissipative couplings, in which the left-right couplings have equal strengths but the phases do not satisfy the complex conjugation. Previous realizations of NHSE typically require unequal left-right couplings or on-site gain and loss. In this Letter we find that when combined with the multichannel interference provided by a periodic dissipative-coherent coupling structure, the dissipative couplings can lead to unequal left-right couplings, inducing NHSE. Moreover, we show that the non-Hermiticity induced by dissipative couplings can be fully transformed into nonreciprocity-type non-Hermiticity without bringing extra gain-loss-type non-Hermiticity. Thus, this mechanism enables unidirectional energy transmission without introducing additional insertion loss. Our work opens a different avenue for the study of non-Hermitian topological effects and the design of directional optical networks.

We experimentally realize a nanoscale stochastic Stirling heat engine operating in the underdamped regime. The setup involves an optically levitated silica particle that is subjected to a power-varying optical trap and periodically coupled to a cold or hot reservoir via switching on or off of the active feedback cooling. We conduct a systematic investigation of the engine's performance and find that both the output work and efficiency approach their theoretical limits under quasistatic conditions. Furthermore, we examine the dependence of the output work fluctuation on the cycle time and the temperature difference between the hot and cold reservoirs. We observe that the distribution has a Gaussian profile in the quasistatic regime, whereas it becomes asymmetric and non-Gaussian as the cycle duration time decreases. This non-Gaussianity is qualitatively attributed to the strong autocorrelation of the particle's position within a cycle in the nonequilibrium regime. Our experiments provide valuable insights into stochastic thermodynamics in the underdamped regime and open up possibilities for the design of future nanomachines.

With the advent of digital and analog quantum simulation experiments, it is now possible to experimentally simulate the dynamics of quantum many-body lattice systems and make site-resolved measurements. These experiments make it pertinent to consider the probability of getting any specific measurement outcome, which we call the signal, on placing multiple detectors at various sites while simulating the dynamics of a quantum many-body lattice system. In this work we formulate and investigate this problem, introducing the concept of quantum many-body detection probability (QMBDP), which refers to the probability of detecting a chosen signal at least once in a given time. We show that, on tuning some Hamiltonian parameters, there can be sharp transition from a regime where the QMBDP is approximately equal to one to a regime where the QMBDP is approximately equal to zero. Most notably, the effects of such a transition can be observed at a single trajectory level. This is not a measurement-induced transition, but rather a nonequilibrium transition reflecting opening of a specific type of gap in the many-body spectrum. We demonstrate this in a single-impurity nonintegrable model, where changing the many-body interaction strength brings about such a transition. Our findings suggest that instead of measuring expectation values, single-shot stroboscopic measurements could be used to observe nonequilibrium transitions.

Driving and dissipation can stabilize Bose-Einstein condensates. Using Keldysh field theory, we analyze this phenomenon for Markovian systems that can comprise on-site two-particle driving, on-site single-particle and two-particle loss, as well as edge-correlated pumping. Above the upper critical dimension, mean-field theory shows that pumping and two-particle driving induce condensation right at the boundary between the stable and unstable regions of the noninteracting theory. With nonzero two-particle driving, the condensate is gapped. This picture is consistent with the recent observation that, without symmetry constraints beyond invariance under single-particle basis transformations, all gapped quadratic bosonic Liouvillians belong to the same phase. For systems below the upper critical dimension, the edge-correlated pumping penalizes high-momentum fluctuations, rendering the theory renormalizable. We perform the one-loop renormalization group analysis, finding a condensation transition inside the unstable region of the noninteracting theory. Interestingly, its critical behavior is determined by a Wilson-Fisher-like fixed point with universal correlation-length exponent $\nu =0.6$ in three dimensions.

Applying a magnetic field as a method for tuning the frequency of Autler-Townes splitting for Rydberg electrometry has recently been demonstrated. In this Letter, we provide a theoretical understanding of Rydberg electromechanically-induced-transparency signals of alkali metal atoms in the presence of a large magnetic field, as well as demonstrate some advantages of this technique over traditional Autler-Townes-based electrometry. We show that a strong magnetic field provides a well-defined quantization axis regardless of the optical field polarizations; we demonstrate that by separating the $m_J$ levels of the Rydberg state, we can perform an Autler-Townes splitting with a single participating dipole moment, and we demonstrate recovery of signal strength by populating a single $m_J$ level using circularly polarized light.

We experimentally test the Crooks fluctuation theorem in a quantum spin system. Our results show that the Crooks fluctuation theorem is valid for different speeds of the nonequilibrium processes and under various effective temperatures. Work is not an observable in quantum systems, which makes tests of quantum thermodynamic theorems challenging. In this work, we develop high-fidelity single-shot readouts of a single nuclear spin in diamond and implement the two-point work measurement protocol, enabling a direct experimental test of the Crooks fluctuation theorem. Our results provide quantum insight into fluctuations and the methods we develop can be utilized to study other quantum thermodynamic theorems.

We introduce a local spectroscopic method in real space to probe the topological properties of a circuit quantum electrodynamics (cQED) array generalizing previous approaches from one to two dimensions in the plane. As an application, we develop the theory of microwave light propagating in the local probe capacitively coupled to the cQED array associated to a bosonic Haldane model. Interestingly, we show that the measured reflection coefficient, resolved in frequency through the resonance, reveals the model's geometrical properties and topological phase transition. We discuss the role of physical parameters such as the lifetime of the light modes and stability towards local disorder related to further realizations.

We present a simple null test of a dimension of a quantum system, using a single repeated operation in the method of delays, assuming that each instance is identical and independent. The test is well suited to current feasible quantum technologies, with programed gates. We also analyze weaker versions of the test, assuming unitary or almost unitary operations, and derive expressions for the statistical error. The feasibility of the test is demonstrated on IBM Quantum. The failure in one of the tested devices can indicate a lack of identity between subsequent gates or an extra dimension in the many worlds/copies model.

A theoretical study of the orientation-dependent attoclock shift in photoelectron momentum distributions generated by ionization of ${\mathrm{HeH}}^{+}$ by a counter-rotating two-color bicircular laser field is presented. Solutions of the two-dimensional time-dependent Schrödinger equation are extrapolated to the adiabatic limit and compared to two-step trajectory models. The trajectory models are sensitive to the choice of the tunnel exit point, which depends on the dipole moment and polarizability tensor of the molecule. Using a suitable trajectory model, we are thus able to reconstruct these molecular properties from the momentum distributions within about 7% deviation from the exact values.

Realizing efficient resonant coupling between spins of different energy scales has significant applications in spin-based quantum technologies, such as quantum sensing. We find that spins with disparate energies can exhibit efficient resonant coupling through the introduction of uneven energy modulation. In this study we apply our proposed method to a nitrogen-vacancy center in close proximity to nuclei. Computational simulations demonstrate that a specific dynamical switching of the electron-spin Rabi frequency enables efficient electron-nuclear coupling, yielding a substantially stronger quantum sensing signal and dynamic nuclear polarization compared to existing methods. This approach holds promise for applications in high-field nanoscale nuclear magnetic resonances as well as for low-power quantum control of nuclear spins.