Precision measurements play a pivotal role in testing theoretical models and exploring new physics. Linear Ramsey interferometer is widely employed for measuring physical quantities, enhancing quantum metrology even approaching the Heisenberg limit. However, the linear interferometer is notably susceptible to detection noise, which limits their practical applications. In this paper, we propose an extended SU(1, 1) echo method to realize a generalized nonlinear interferometer, which is resilient to the detection noise. We demonstrate the utility of this approach by applying it to two distinct models: the Lipkin-Meshkov-Glick model and spin-mixing dynamics. Numerical simulations confirm the effectiveness of our proposed method. Additionally, we identify a trade-off in selecting the echoing conditions, which can be utilized to further enhance estimation precision. Our proposal may be easily implemented in many platforms, such as Bose-Einstein condensate, Rydberg atoms, and polar molecules, to enhance the metrology of time and field strength.

We investigate quantum superposition effects in two-dimensional quantum walks of identical particles with different statistics under particle exchange, starting from various different initial configurations. To characterize interparticle correlation dynamics, we focus on joint properties such as two-particle coincidence probabilities and the spread velocity of the interparticle distance. Regarding spatial modes as an environment for the particles internal degrees of freedom, we study the role played by the particle statistics using standard entanglement witnesses, showing that particles possessing fermionic statistics are more resistant to thermalize with their environment. We analyze the presence of multipartite entanglement in the system's degrees of freedom through the Quantum Fisher Information, revealing that fermionic states generated during the walk are better suited to perform quantum metrology tasks. Finally, we discuss the potential for implementing this model using integrated photonic circuits by exploiting $N$-partite entanglement between individual photons.

The conditions for transforming pure entangled states under local operations and classical communication (LOCC) are well understood. A natural question then arises: Can we determine the transformation conditions for mixed entangled states under LOCC based on the properties of their pure-state ensembles? While much effort has been devoted to this issue, in this paper, we rule out this possibility. Our findings address several open questions, including the following: (i) The conditions $E_f^{\mathrm{CR}}\left(\rho \right)\ge E_f^{\mathrm{CR}}\left(\sigma \right)$ for all convex roof entanglement measures $E_f^{\mathrm{CR}}$ are insufficient to guarantee the existence of an LOCC transformation ${\mathrm{\Lambda }}^L(·)$ from $\rho$ to $\sigma$, and (ii) the inequalities ${\sum }_j{p}_{j}E\left({\phi }_j\right)\ge {\sum }_l{q}_{l}E\left({\psi }_l\right)$ for all entanglement monotones $E$ are not sufficient to ensure the existence of an LOCC transformation from $\{p_j,|{\phi }_j\rangle \}$ to $\{q_l,|{\psi }_l\rangle \}$.

This work explores the implications of the exclusivity principle (EP) in the context of quantum and postquantum correlations. We first establish a key technical result demonstrating that given the set of correlations for a complementary experiment, the EP restricts the maximum set of correlations for the original experiment to the antiblocking set. Based on it, we can prove our central result: if all quantum behaviors are accessible in Nature, the EP guarantees that no postquantum behaviors can be realized. This can be seen as a generalization of the result of B. Amaral et al. [Phys. Rev. A 89, 030101(R) (2014)], to a wider range of scenarios. It also provides novel insights into the structure of quantum correlations and their limitations.

A potential approach for demonstrating quantum advantage is using quantum computers to simulate fermionic systems. Quantum algorithms for fermionic system simulation usually involve the Hamiltonian evolution and measurements. However, in the second quantization representation, the number of terms in many fermion system Hamiltonians, such as molecular Hamiltonians, is substantial, approximately $O\left(N^4\right)$, where $N$ is the number of molecular orbitals. Due to this, the computational resources required for Hamiltonian evolution and expectation value measurements could be excessively large. To address this, we introduce a grouping strategy that partitions these $O\left(N^4\right)$ Hamiltonian terms into $O\left(N^2\right)$ groups, with the terms in each group mutually commuting. Based on this grouping method, we propose a parallel Hamiltonian evolution scheme that reduces the circuit depth of Hamiltonian evolution by a factor of $N$. Moreover, our grouping measurement strategy reduces the number of measurements needed to $O\left(N^2\right)$, whereas the current best grouping measurement schemes require $O\left(N^3\right)$ measurements. Additionally, we find that measuring the expectation value of a group of Hamiltonian terms requires fewer repetitions than measuring a single term individually, thereby reducing the number of quantum circuit executions. Our approach saves a factor of $N^3$ in the overall time for Hamiltonian evolution and measurements, significantly decreasing the time required for quantum computers to simulate fermionic systems.

High-precision, robust quantum gates are essential components in quantum computation and information processing. In this study, we present an alternative perspective, exploring the potential applicability of quantum gates that exhibit heightened sensitivity to errors. We investigate such sensitive quantum gates, which, beyond their established use in in vivo nuclear magnetic resonance spectroscopy and polarization optics, may offer significant utility in the other areas where selectivity, filtering, sensing, localization, or addressing properties are of interest. Utilizing the composite pulses technique, we derive three fundamental quantum gates with narrowband and passband characteristics—the X (not) gate, the hadamard gate, and gates enabling arbitrary rotations. To systematically design these composite pulse sequences, we introduce the SU(2), modified-SU(2), and regularization random search methodologies. These approaches demonstrate superior performance compared to established sequences in the literature, including NB1, SK1, and PB1.

Anomalies in the rotational structure of ${}^{86}\mathrm{Sr}$ ${}^{3}S_1$ dimer ultralong-range Rydberg molecules created in a cold strontium gas by two-photon excitation via the intermediate $5s5p$ ${}^{3}P_1$ state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using ${}^{84}\mathrm{Sr}$ ${}^{1}S_0$ and ${}^{3}S_1$, and ${}^{86}\mathrm{Sr}$ ${}^{1}S_0$ dimers display no similar behavior, indicating that the observed behavior is peculiar to ${}^{86}\mathrm{Sr}$ triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for ${}^{84}\mathrm{Sr}$ and ${}^{86}\mathrm{Sr}$, or the interchange of spin and rotational angular momentum.

We performed a four-body coincidence measurement involving ${\mathrm{H}}^{+}, {\mathrm{H}}^{+}, {\mathrm{Cl}}^{+}$, and ${\mathrm{Cl}}^{+}$ fragments generated by strong field ionization of the HCl dimer. The energy correlation maps reveal the rapid explosion of two protons and the slow repulsion between two ${\mathrm{Cl}}^{+}$ ions during the four-body fragmentation. Moreover, the kinetic energy of the fragments relative to the emission angles provides valuable insights into how the motion of the proton affects the energy distribution between ions. We also performed ab initio calculations to track the real-time movements of the four fragments. The simulations reveal the influence of fast-moving protons on the comparatively slow fragmentation process of ${\mathrm{Cl}}^{+}$ ions. This comprehensive approach sheds light on the dynamics and offers valuable insights into the ultrafast fragmentation of molecular clusters.

The transition energies and properties of the ${\mathrm{Ir}}^{17+}$ ion are calculated using the Kramers-restricted configuration-interaction (KRCI) and Fock-space coupled-cluster (FSCC) methods within the Dirac-Coulomb-Gaunt Hamiltonian framework. These calculations show several forbidden optical transitions between the $4f^{13}5s$ ground state and the $4f^{14}$ and $4f^{12}5s^2$ excited states, underscoring their potential as candidates for optical clock applications. Additionally, key properties of the ground and low-lying excited states are reported, including Landé $g_J$ factors, lifetimes, electric dipole polarizabilities, electric quadrupole moments, hyperfine structure constants, relativistic sensitivities, Lorentz-invariance coefficient tensor, and isotope shifts. The excellent agreement between the results from the KRCI and FSCC methods demonstrates the robustness of the calculations and confirms the reliability of the proposed clock transitions.

We study the quantum evolution of one-dimensional Bose gases immediately after several variants of high-energy quenches, both theoretically and experimentally. Using the advantages conveyed by the relative simplicity of these nearly integrable many-body systems, we are able to differentiate the behaviors of two distinct but often temporally overlapping processes, hydrodynamization and local prethermalization. We show that the hydrodynamization epoch is itself characterized by two independent timescales, an oscillation period and an observable-dependent damping time. We also show how the existence of a hydrodynamization epoch depends on the exact nature of the high-energy quench. There is a universal character to our findings, which can be applied to the short-time behavior of any interacting many-body quantum system after a sudden high-energy quench. We specifically discuss its potential relevance to heavy-ion collisions.

Can the state-space of $d$-dimensional quantum theory be derived from studying the behavior of a single “reference” measuring device? The answer is yes, if the measuring device corresponds to a complex-projective 3-design. In this privileged case, not only does each quantum state correspond to a probability distribution over the outcomes of a single measurement, but also the probability distributions which correspond to quantum states can be elegantly characterized as those which respect a generalized uncertainty principle. The latter takes the form of a lower-bound on the variance of a natural class of observables as measured by the reference. We give simple equations which pure-state probability distributions must satisfy, and contextualize these results by showing how 3-designs allow the structure-coefficients of the Jordan algebra of observables to be extracted from the probabilities which characterize the reference measurement itself. This lends credence to the view that quantum theory ought to be primarily understood as a set of normative constraints on probability assignments which reflect nature's lack of hidden variables and further cements the significance of 3-designs in quantum information science.

In open quantum systems theory, reduced models are invaluable for conceptual understanding and computational efficiency. Adiabatic elimination is a useful model reduction method for systems with separated timescales, where a reduced model is derived by discarding rapidly decaying degrees of freedom. So far, adiabatic elimination has been formulated using a geometric approach, which provides a versatile and general framework. This article introduces a reformulation of adiabatic elimination through the framework of the time-convolutionless (TCL) master equation, a widely recognized tool for computing projected time evolution in open quantum systems. We show that the TCL master equation formulation yields results equivalent to those obtained from the geometric formulation. By applying the TCL master equation formulation to typical examples, we demonstrate a practical methodology for performing adiabatic elimination calculation. This study not only bridges two previously independent approaches, thereby making the adiabatic elimination method accessible to a broader audience, but also enables the analysis of complex cases that are challenging within the geometric formulation. Additionally, it reveals a geometric interpretation of the TCL master equation formalism.

We propose how to generate the entanglement of two long-lived phonon modes in a circuit quantum acoustodynamics system, which consists of a multimode high-frequency bulk acoustic wave resonator and a transmon-type superconducting qubit. Two acoustic modes couple to the qubit through piezoelectric interaction, and the qubit is driven by a microwave field. Under the condition of far detuning between the qubit and acoustic modes, the qubit can be eliminated adiabatically, thus establishing the indirect interaction between the two acoustic modes. We demonstrate that such an indirect interaction can be a parametric-amplification-type interaction by appropriately choosing the drive frequency and strength, so the entanglement between acoustic modes can be created by the direct unitary evolution. We numerically analyze the parameter conditions for generating the entanglement in detail and evaluate the influence of system dissipations and noise. The results show that the scheme can be realized using currently available parameters and has strong robustness against the dissipations and the environmental temperature. This work may provide an efficient resource for the quantum information processing based on the phononic systems.

We consider the problem of quantum error correction (QEC) for non-Markovian noise. Using the well-known Petz recovery map, we first show that conditions for approximate QEC can be easily generalized for the case of non-Markovian noise in the strong-coupling regime where the noise map becomes non-completely-positive at intermediate times. While certain approximate QEC schemes are ineffective against quantum non-Markovian noise, in the sense that the fidelity vanishes in finite time, the Petz map adapted to non-Markovian noise uniquely safeguards the code space even at the maximum noise limit. Focusing on the case of non-Markovian amplitude damping noise, we further show that the non-Markovian Petz map also outperforms the standard, stabilizer-based QEC code. Since implementing such a non-Markovian map poses practical challenges, we also construct a Markovian Petz map that achieves a similar performance, with only a slight compromise on the fidelity. Finally, we also study an example of non-Markovian Pauli noise, namely the non-Markovian dephasing channel. In this case, we show that the non-Markovian Petz recovery preserves the code space even at the high-noise limit for certain noise-adapted codes, whereas the Markovian Petz and stabilizer recoveries are ineffective.

We systematically investigate Landau-Zener-Stückelberg-Majorana (LZSM) interference under chiral-mirror-like symmetry and propose its application to nonadiabatic topological transport of edge states. Protected by this symmetry, complete destructive interference emerges and can be characterized through occupation probability. This symmetry-protected LZSM interference enables state transitions to be achieved within remarkably short timescales. To demonstrate our mechanism, we provide two distinctive two-level systems as examples and survey them in detail. By tuning evolution speed or increasing holding time, the complete destructive interferences are observed. Furthermore, we make use of this mechanism for topological edge states of Su-Schrieffer-Heeger (SSH) chain by taking them as an isolated two-level system. Through carefully designed time sequences, we construct symmetry-protected LZSM interference of topological edge states, enabling nonadiabatic topological transport. Our work unveils an alternative way to study quantum control, quantum state transfer, and quantum communication via nonadiabatic topological transport.

We present the dynamical multipartite entanglement, which is in terms of the quantum Fisher information, of a generalized Tavis-Cummings (TC) model introducing the $XY$ spin interaction. Since our model cannot be solved exactly, the effective description of the model is theoretically derived and numerically examined. By the Holstein-Primakoff transformation, we show the bridge from the generalized TC model to the central spin model. We also discuss the effect of the temperature, the coupling constant, and the magnetic field on the dynamical multipartite entanglement in the central spin model, where the central spin is initially unentangled. Strong coupling and low temperature are necessary conditions for a genuine multipartite entanglement in the $XY$ model. The former governs the maximum entanglement, while the latter plays a crucial role in stabilizing the entanglement. The magnetic field modulates the period and amplitude of multipartite entanglement, primarily affecting the stable waveform of it. Our findings allow for a better comprehension of dynamical multipartite entanglement and provide a viable experimental platform for driving advances in quantum metrology and quantum information processing.

We explore the elastic scattering of nonrelativistic electrons in the form of Bessel-Gaussian (BG), standard Laguerre-Gaussian (sLG), and elegant Laguerre-Gaussian (eLG) packets on atomic targets in the generalized Born approximation. Scattering by hydrogenlike, iron, silver, and golden targets is considered. The incident electron carries a nonzero orbital angular momentum, while sLG and eLG packets have a definite radial quantum number $n$ as well. In the scattering of sLG and eLG wave packets by a macroscopic target, sensitivity of the average cross section to the orbital angular momentum is observed, which is absent for BG packets. We discuss the potential experimental realization of vortex-electron wave packets of these three types. The distinguishing features in the scattering results can be employed for imaging purposes and revelation of the packet properties in experiments.