Long-Lived Bloch Oscillations with Bosonic Sr Atoms and Application to Gravity Measurement at the Micrometer Scale

Abstract

We report on the observation of Bloch oscillations on the unprecedented time scale of several seconds. The experiment is carried out with ultracold bosonic 88 Sr atoms loaded into a vertical optical standing wave. The negligible atom-atom elastic cross section and zero angular momentum in the ground state makes 88 Sr an almost ideal Bose gas, insensitive to typical mechanisms of decoherence due to thermalization and external stray fields. The small size of the system enables precision measurements of forces at micrometer scale. This is a challenge in physics for studies of surfaces, Casimir effects, and searches for deviations from Newtonian gravity predicted by theories beyond the standard model. DOI: 10.1103/PhysRevLett.97.060402 PACS numbers: 03.75.ÿb, 04.80.ÿy, 32.80.ÿt Quantum devices based on ultracold atoms show unprecedented features. Atom interferometry is used for precision inertial sensors [1,2], to measure fundamental constants [3][4][5], and for testing relativity [6].Here we show that, using laser-cooled strontium atoms in optical lattices, persistent Bloch oscillations are observed for a time ' 10 s, and gravity is determined with ppm sensitivity on a micrometer scale. The small size enables precision measurements of forces at micrometer scale. This is a challenge in physics for studies of surfaces, Casimir effects [7], and searches for deviations from Newtonian gravity predicted by theories beyond the standard model [8,9]. The insensitivity to stray fields and collisions makes Sr in optical lattices, a candidate also for future clocks [10], a unique sensor for small-scale forces with better performances and reduced complexity compared to proposed schemes using degenerate Bose [11] or Fermi [12] gases. This enables new experiments on gravity at unexplored short distances.The confinement of ultracold atoms in optical lattices, regular structures created by interfering laser beams where the atoms are trapped by the dipole force, provides clean model systems to study condensed-matter physics problems [13]. In particular, under the influence of a periodic potential and a weak uniform force, the atomic momentum changes periodically across the first Brillouin zone, a phenomenon known as Bloch oscillations [14]. Bloch oscillations were predicted for electrons in a periodic crystal potential in the presence of a static electric field [15] but could not be observed in natural crystals because of the scattering of electrons by the lattice defects. They were directly observed using atoms in an optical lattice [16].In our experiment, laser-cooled 88 Sr atoms are trapped in a one-dimensional vertical optical lattice. The combination of the periodic optical potential and the linear gravitational potential gives rise to Bloch oscillations at a frequency B given bywhere m is the atomic mass, g is the acceleration of gravity, L is the wavelength of the light producing the lattice, and h is Planck constant. Since L , m, and h are well known, the force along the lattice axis can be determined by measuring the B...

Characterization of a simultaneous dual-species atom interferometer for a quantum test of the weak equivalence principle

“…Many experiments and projects worldwide, also prove that quantum sensors appear to be very promising tools for exploring many aspects of fundamental physics as the determination of the fine-structure constant α [16] and the Newtonian gravity constant G [17,18], the detection of gravitational waves [19], the exploration of shortrange forces [20,21] and quantum based tests of the Weak Equivalence Principle (WEP) [22][23][24][25][26].…”

Long-Living Bloch Oscillations of Matter Waves in Periodic Potentials

“…Apart its fundamental significance, the interest in BO arises mainly from perspectives of their practical applications. In this context we mention the use of BO for metrological tasks, including relatively precise definition of h/m [8] and measurement of forces at the micrometer scale like the Casimir-Polder force [9] and the gravity [10]. Recently, BO were also suggested as a tool for controlling light in coupled-resonator optical waveguides [11].…”

Atom interferometers and optical atomic clocks: New quantum sensors for fundamental physics experiments in space

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