Hamiltonian engineering of spin-orbit-coupled fermions in a Wannier-Stark optical lattice clock.

Engineering a Hamiltonian system with tunable interactions provides opportunities to optimize performance for quantum sensing and explore emerging phenomena of many-body systems. An optical lattice clock based on partially delocalized Wannier-Stark states in a gravity-tilted shallow lattice supports superior quantum coherence and adjustable interactions via spin-orbit coupling, thus presenting a powerful spin model realization. The relative strength of the on-site and off-site interactions can be tuned to achieve a zero density shift at a "magic" lattice depth. This mechanism, together with a large number of atoms, enables the demonstration of the most stable atomic clock while minimizing a key systematic uncertainty related to atomic density. Interactions can also be maximized by driving off-site Wannier-Stark transitions, realizing a ferromagnetic to paramagnetic dynamical phase transition.

Diagnosis, treatment, outcome, and reasons for delayed treatment of cryptorchidism with torsion in children: a 16-year retrospective study in a large pediatric medical center.

We describe and summarize the diagnosis, treatment, and reasons for delayed treatment of children with cryptorchidism torsion in Children's Hospital of Chongqing Medical University. The study included 19 cases of cryptorchidism torsion. The age of the children ranged from 16 days to 12 years (median: 6 years). The interval from diagnosis to surgery varied from 4 h to 16 days (median: 3 days). Ultrasound was performed in all cases. Fifteen cases had cryptorchidism torsion, 2 cases had a soft tissue mass in the inguinal region, and 2 cases had an inguinal/abdominal teratoma. Five cases were treated with an orchidopexy, 12 cases were treated with orchiectomy, and 2 cases received resection of a testicular tumor. The 5 children with an orchidopexy were followed up from 1 month to 7 years (median: 3 years), with 1 child having a testis retraction and no blood supply. Of the 12 children who had an orchiectomy, three had delayed diagnosis due to family unawareness of the condition, while other delays were due to delayed referral from primary care facilities. The relative rarity and insufficient awareness of cryptorchidism torsion resulted in a low rate of testicular salvage. Therefore, hospitals of all levels should be fully aware of cryptorchidism with torsion and ensure a male child's genital system and inguinal region are examined to improve the success rate of testicular salvage.

Quantum Enhanced Cavity QED Interferometer with Partially Delocalized Atoms in Lattices.

We propose a quantum enhanced interferometric protocol for gravimetry and force sensing using cold atoms in an optical lattice supported by a standing-wave cavity. By loading the atoms in partially delocalized Wannier-Stark states, it is possible to cancel the undesirable inhomogeneities arising from the mismatch between the lattice and cavity fields and to generate spin squeezed states via a uniform one-axis twisting model. The quantum enhanced sensitivity of the states is combined with the subsequent application of a compound pulse sequence that allows us to separate atoms by several lattice sites. This, together with the capability to load small atomic clouds in the lattice at micrometric distances from a surface, make our setup ideal for sensing short-range forces. We show that for arrays of 10^{4} atoms, our protocol can reduce the required averaging time by a factor of 10 compared to unentangled lattice-based interferometers after accounting for primary sources of decoherence.

Collective P-Wave Orbital Dynamics of Ultracold Fermions.

We consider the nonequilibrium orbital dynamics of spin-polarized ultracold fermions in the first excited band of an optical lattice. A specific lattice depth and filling configuration is designed to allow the p_{x} and p_{y} excited orbital degrees of freedom to act as a pseudospin. Starting from the full Hamiltonian for p-wave interactions in a periodic potential, we derive an extended Hubbard-type model that describes the anisotropic lattice dynamics of the excited orbitals at low energy. We then show how dispersion engineering can provide a viable route to realizing collective behavior driven by p-wave interactions. In particular, Bragg dressing and lattice depth can reduce single-particle dispersion rates, such that a collective many-body gap is opened with only moderate Feshbach enhancement of p-wave interactions. Physical insight into the emergent gap-protected collective dynamics is gained by projecting the Hamiltonian into the Dicke manifold, yielding a one-axis twisting model for the orbital pseudospin that can be probed using conventional Ramsey-style interferometry. Experimentally realistic protocols to prepare and measure the many-body dynamics are discussed, including the effects of band relaxation, particle loss, spin-orbit coupling, and doping.

Observation of a transition between dynamical phases in a quantum degenerate Fermi gas.

A proposed paradigm for out-of-equilibrium quantum systems is that an analog of quantum phase transitions exists between parameter regimes of qualitatively distinct time-dependent behavior. Here, we present evidence of such a transition between dynamical phases in a cold-atom quantum simulator of the collective Heisenberg model. Our simulator encodes spin in the hyperfine states of ultracold fermionic potassium. Atoms are pinned in a network of single-particle modes, whose spatial extent emulates the long-range interactions of traditional quantum magnets. We find that below a critical interaction strength, magnetization of an initially polarized fermionic gas decays quickly, while above the transition point, the magnetization becomes long-lived because of an energy gap that protects against dephasing by the inhomogeneous axial field. Our quantum simulation reveals a nonequilibrium transition predicted to exist but not yet directly observed in quenched s-wave superconductors.