Mandip Singh

One-dimensional lattice of permanent magnetic microtraps for ultracold atoms on an atom chip

We report on the loading and trapping of ultracold atoms in a one-dimensional permanent magnetic lattice of period 10 µm produced on an atom chip. The grooved structure which generates the magnetic lattice potential is fabricated on a silicon substrate and coated with a perpendicularly magnetized multilayered TbGdFeCo/Cr film of effective thickness 960 nm. Ultracold atoms are evaporatively cooled in a Z-wire magnetic trap and then adiabatically transferred to the magnetic lattice potential by applying an appropriate bias field. Under our experimental conditions trap frequencies of up to 90 kHz in the magnetic lattice are measured and the atoms are trapped at a distance of less than 5 µm from the surface with a measured lifetime of about 450 ms. These results are important in the context of studies of quantum coherence of neutral atoms in periodic magnetic potentials on an atom chip.

Einstein-Podolsky-Rosen correlations from colliding Bose-Einstein condensates

i ¯ x0p) |pA|−pB, where x and p denote position and momentum, x0 is a constant, and indices label the two particles. In this paper, following the experimental approach of Ref. (13), we consider a Bose-Einstein condensate (BEC) of metastable helium-4 ( 4 He ∗ ). Via interactions with lasers, the particles are outcoupled from the trap, brought to collision, and fall on a detector. The collisions prepare atom pairs in a three-dimensional version of the EPR state with fixed absolute momenta. While the idealized EPR state would have to be created everywhere in space, our pairs are created in a finite space volume. We propose to test the entanglement in a double-double-slit experiment or via ghost interference. We start with a short review of the procedure described in Ref. (13): 4 He ∗ atoms of mass m � 6.646 × 10 −27 kg are magnetically trapped and form a cigar-shaped BEC along the (horizontal) x direction. One employs two σ -polarized laser beams counterpropagating horizontally along the +x and −x directions and a π -polarized laser beam from the top along the −z direction fulfilling the Raman condition, all with a wavelength λL � 1.083 μm. They bring the atoms into a magnetically insensitive state and thereby induce a velocity kick in the horizontal ±x directions and a kick upwards along +z. The recoil velocity of each kick is vrec = h λL m � 92 mm/s,

Macroscopic entanglement between a Bose Einstein condensate and a superconducting loop

We theoretically study macroscopic entanglement between a magnetically trapped Bose-Einstein condensate and a superconducting loop. We treat the superconducting loop in a quantum superposition of two different flux states coupling with the magnetic trap to generate macroscopic entanglement. The scheme also provides a platform to investigate interferometry with an entangled Bose Einstein condensate and to explore physics at the quantum-classical interface.

Bose-Einstein condensate of metastable helium for quantum correlation experiments

We report on the realization of Bose-Einstein condensation of metastable helium-4. After exciting helium to its metastable state in a novel pulse-tube cryostat source, the atomic beam is collimated and slowed. We then trap several 10^8 atoms in a magneto-optical trap. For subsequent evaporative cooling, the atoms are transferred into a magnetic trap. Degeneracy is achieved with typically a few 10^6 atoms. For detection of atomic correlations with high resolution, an ultrafast delay-line detector has been installed. Consisting of four quadrants with independent readout electronics that allow for true simultaneous detection of atoms, the detector is especially suited for quantum correlation experiments that require the detection of correlated subsystems. We expect our setup to allow for the direct demonstration of momentum entanglement in a scenario equivalent to the Einstein-Podolsky-Rosen gedanken experiment. This will pave the way to matter-wave experiments exploiting the peculiarities of quantum correlations.

Dynamics of reflection of ultracold atoms from a periodic one-dimensional magnetic lattice potential

We report on an experimental study of the dynamics of the reflection of ultracold atoms from a periodic one-dimensional magnetic lattice potential. The magnetic lattice potential of period 10 {mu}m is generated by applying a uniform bias magnetic field to a microfabricated periodic structure on a silicon wafer coated with a multilayered TbGdFeCo/Cr magneto-optical film. The effective thickness of the magnetic film is about 960 nm. A detailed study of the profile of the reflected atoms as a function of externally induced periodic corrugation in the potential is described. The effect of angle of incidence is investigated in detail. The experimental observations are supported by numerical simulations.

Steep atomic dispersion induced by velocity-selective optical pumping

We demonstrate a method of preparation of broadband sign-reversible dispersion in alkali vapour based on velocity-selective optical pumping. The refractive index in Rb vapour has been measured using a heterodyne method. The magnitudes of the normal and anomalous dispersion, which are almost constant over a spectral region of approximately 40 MHz, can lead to a reduced (V(g) approximately c/230) or negative (V(g) approximately -c/27) group velocity of light.

Quantum Stern-Gerlach experiment and path entanglement of a Bose-Einstein condensate

In this paper, a quantum Stern-Gerlach thought experiment is introduced where, in addition to the intrinsic angular momentum of an atom, the magnetic field is also treated quantum mechanically. A freely falling spin polarised Bose-Einstein condensate passes close to a flux-qubit and interacts with the quantum superimposed magnetic field of the flux-qubit. Such an interaction results a macroscopic quantum entanglement of the path of a Bose-Einstein condensate with the magnetic flux quantum state of the flux-qubit. In this paper, three regimes of coupling between the flux-qubit and a freely falling Bose-Einstein condensate are discussed. The decoherence time limit required to achieve a strong coupling regime is also estimated. This paper also explores, how to produce a path entangled Bose-Einstein condensate where, the condensate can be located at physically distinct locations simultaneously. Paper provides new fundamental insights about the foundations of the quantum Stern-Gerlach experiment.

Trapping of ultracold atoms in a 10 μm-period permanent magnetic lattice

We report the realization of trapping of ⁸⁷Rb | F=1, m<inf>F</inf> = −1〉 atoms at temperature of 1–2 μK in a 10 μm-period 1D magnetic lattice constructed from a TbGdFeCo magnetic microstructure on an atom chip.

A Magnetic Lattice Atom Chip for Ultracold Quantum Gases

We describe a 1-D magnetic lattice atom chip, with a period of 10 µm, to trap multiple clouds of87Rb F=1 atoms at temperatures down to 10 µK with trap lifetimes of 8 s.