The Standard Model of particle physics is known to be incomplete. Extensions to the Standard Model, such as weak-scale supersymmetry, posit the existence of new particles and interactions that are asymmetric under time reversal (T) and nearly always predict a small yet potentially measurable electron electric dipole moment (EDM), d(e), in the range of 10(-27) to 10(-30) e·cm. The EDM is an asymmetric charge distribution along the electron spin (S(→)) that is also asymmetric under T. Using the polar molecule thorium monoxide, we measured d(e) = (-2.1 ± 3.7stat ± 2.5syst) × 10(-29) e·cm. This corresponds to an upper limit of |d(e)| < 8.7 × 10(-29) e·cm with 90% confidence, an order of magnitude improvement in sensitivity relative to the previous best limit. Our result constrains T-violating physics at the TeV energy scale.

We study non-equilibrium dynamics for an ensemble of tilted one-dimensional atomic Bose-Hubbard chains after a sudden quench to the vicinity of the transition point of the Ising paramagnetic to anti-ferromagnetic quantum phase transition. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly-occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response.PACS numbers: 37.10. Jk, 67.85.Hj, 75.10.Pq, 05.30.Rt Ultracold atomic ensembles confined in optical lattice potentials have proven to offer unique access to the study of strongly correlated quantum phases of matter [1, 2]. Unprecedented control over system parameters as well as exceptionally good isolation from the environment allow for implementation and quantitative simulation of lattice Hamiltonians [3, 4], not only bridging the fields of atomic and condensed matter physics in the study of ground-state phases, but also opening fundamentally new opportunities to explore out-of-equilibrium physics in essentially closed quantum systems [5, 6]. For example, the rapid time-dependent control available over system parameters makes it possible to observe dynamics arising from a quantum quench, where a parameter such as the lattice depth is changed suddenly in time [7][8][9]. Recently it was demonstrated that 1D chains of bosonic atoms with a superimposed linear gradient potential exhibit a quantum phase transition to a density-wave-ordered state, in which empty sites alternate with doubly-occupied sites ("doublons"). Beginning in a Mott-insulator phase of a BoseHubbard (BH) system [10, 11], where the on-site interactions dominate over tunneling and the atoms are exponentially localized on individual lattice sites, a gradient potential is added until the potential difference between adjacent sites matches the on-site interaction energy, and atoms can again resonantly tunnel. This was monitored for individual 1D chains with a length of about 10 sites with the quantum gas microscopy technique [12], and effectively maps onto a 1D Ising model [13], making it possible to simulate the transition from 1D paramagnetic (PM) spin chains to anti-ferromagnetic (AFM) spin chains in the context of ultracold atoms.In this letter, we explore the dynamics of a quantum quench for bosonic atoms in such a tilted optical lattice [14][15][16]. Specifically, we quench the strength of the tilt to be near the phase transition point between PM and AFM regimes, and hence take the system far out of equilibrium, inducing strong oscillations in the number of doublons, which we detect through molecule formation. We find clear indications for the collective character of the ensuing dynamics.We consider a 1D atomic ensemble in a tilted optical lattice potential near zero temperature. For sufficiently weak interaction energy, much smaller ...

We experimentally investigate the quantum motion of an impurity atom that is immersed in a strongly interacting one-dimensional Bose liquid and is subject to an external force. We find that the momentum distribution of the impurity exhibits characteristic Bragg reflections at the edge of an emergent Brillouin zone. While Bragg reflections are typically associated with lattice structures, in our strongly correlated quantum liquid they result from the interplay of short-range crystalline order and kinematic constraints on the many-body scattering processes in the one-dimensional system. As a consequence, the impurity exhibits periodic dynamics that we interpret as Bloch oscillations, which arise even though the quantum liquid is translationally invariant. Our observations are supported by large-scale numerical simulations.A skydiver accelerated by the gravitational force approaches a constant drift velocity due to friction with the surrounding medium. In the quantum realm, dynamics can be significantly richer. For example, a quantum particle accelerated in a periodic crystal potential does not move at all on average but rather undergoes a periodic motion known as Bloch oscillations [1, 2]. Such an oscillatory motion is a direct consequence of the periodic momentum-dependence of the eigenstates in a lattice potential and arises from continuous translational symmetry breaking. Bloch oscillations have been observed for electrons in solid state systems [3] and have been investigated in detail with ultracold atoms in optical lattices [4][5][6][7][8]. One might expect that a quantum liquid, which is fully translational invariant, or in other words does not have an imprinted lattice structure, would preclude such striking dynamics. However, recent theoretical studies [9, 10] suggest that Bloch oscillations can emerge also in the presence of a continuous translational symmetry. In particular, for impurity atoms immersed in one-dimensional (1D) quantum liquids such dynamics is expected to arise due to strong quantum correlations, which lead to effective crystal-like properties. Yet, suitable conditions for that phenomenon are debated [11]. Ultracold quantum gases provide an ideal setting to experimentally study the dynamics of impurity particles coupled to host environments [12][13][14][15][16] due to excellent parameter control, precise initial state preparation, and decoupling from the environment. FIG. 1: Concept of the experiment. (A)We realize an ensemble of 1D Bose gases in tubes formed by two pairs of counter-propagating and interfering laser beams. In each tube, a single strongly interacting impurity (green sphere) is immersed in the correlated host gas (black spheres) and is accelerated by gravity (green arrow). Inset: Scattering length as for collisions between the atoms in the host gas (dashed line) and between the impurity and the host atoms (solid line) as a function of the magnetic field B. (B) The excitation spectrum of the impurity coupled to the 1D Bose liquid is a 2kF periodic function of the system's t...

Quantum tunneling is at the heart of many low-temperature phenomena. In strongly correlated lattice systems, tunneling is responsible for inducing effective interactions, and long-range tunneling substantially alters many-body properties in and out of equilibrium. We observe resonantly enhanced long-range quantum tunneling in one-dimensional Mott-insulating Hubbard chains that are suddenly quenched into a tilted configuration. Higher-order tunneling processes over up to five lattice sites are observed as resonances in the number of doubly occupied sites when the tilt per site is tuned to integer fractions of the Mott gap. This forms a basis for a controlled study of many-body dynamics driven by higher-order tunneling and demonstrates that when some degrees of freedom are frozen out, phenomena that are driven by small-amplitude tunneling terms can still be observed.

Rotational levels of molecular free radicals can be tuned to degeneracy using laboratory-scale magnetic fields. Because of their intrinsically narrow width, these level crossings of opposite-parity states have been proposed for use in the study of parity-violating interactions and other applications. We experimentally study a typical manifestation of this system using 138 BaF. Using a Stark-mixing method for detection, we demonstrate level-crossing signals with spectral width as small as 6 kHz. We use our data to verify the predicted lineshapes, transition dipole moments, and Stark shifts, and to precisely determine molecular magnetic g-factors. Our results constitute an initial proof-ofconcept for use of this system to study nuclear spin-dependent parity violating effects.PACS numbers: 32.80. Ys, 12.15.Mm, 21.10.Ky It has been suggested that diatomic molecules could be used as a system to measure classes of parity-violating (PV) electroweak interactions that are difficult to access through other means [1][2][3]. The level structure of diatomic free radicals systematically makes it possible to tune states of opposite parity to near degeneracy, using a magnetic field such that the Zeeman shift of the electron spin matches the rotational splitting. Near such a level crossing, the mixing of these long-lived states due to nuclear spin-dependent (NSD) PV interactions is greatly enhanced [4]. This should make it feasible to measure small, poorly understood effects such as those due to nuclear anapole moments and axial hadronic-vector electronic electroweak couplings [3,5,6]. This type of level crossing has also been identified as an attractive system for quantum simulations of conical intersections [7] or magnetic excitons [8], and for sensitive detection of electric fields [9].Here we report an experimental study of Zeeman-tuned rotational level crossings in 138 BaF. Using an electric field pulse to induce transitions between the near-degenerate levels, we demonstrate the ability to understand and control the system with energy resolution at the kHz scale, as desired for the measurement of nuclear spin-dependent PV effects in similar systems. By measuring the magnetic field at several crossings, we extract precise values for poorly known magnetic g-factors; also, by studying transfer efficiency vs. electric field, we deduce values for electric dipole matrix elements between the crossing levels, and for off-resonant Stark shifts not previously con- * e-mail: sidney.cahn@yale. 138 Ba is spinless. In the absence of external fields, the lowest energy levels are described by the Hamiltonianwhere N is the rotational angular momentum, S = 1/2 is the electron spin, and n is a unit vector along the internuclear axis ( = 1 throughout) [11,12]. All parameters of H 0 have been precisely measured [13][14][15]. The rotational constant B is much larger than the spin-rotation (SR) constant γ, the hyperfine (HF) constants b and c, and the centrifugal correction constant D; thus N is a good quantum number, with eigenstates of energ...