arXiv subjects

D. S. Naik

Publications and source records attributed to D. S. Naik.

10 recordsLinked to original sources

arXiv2021

Fast control of atom-light interaction in a narrow linewidth cavity

We propose a method to exploit high finesse optical resonators for light assisted coherent manipulation of atomic ensembles, overcoming the limit imposed by the finite response time of the cavity. The key element of our scheme is to rapidly switch the interaction between the atoms and the cavity field with an auxiliary control process as, for example, the light shift induced by an optical beam. The scheme is applicable to many different atomic species, both in trapped and free fall configurations, and can be adopted to control the internal and/or external atomic degrees of freedom. Our method will open new possibilities in cavity-aided atom interferometry and in the preparation of highly non-classical atomic states.

physics.atom-ph↗

arXiv2020

A control hardware based on a field programmable gate array for experiments in atomic physics

Experiments in Atomic, Molecular, and Optical (AMO) physics require precise and accurate control of digital, analog, and radio frequency (RF) signals. We present a control hardware based on a field programmable gate array (FPGA) core which drives various modules via a simple interface bus. The system supports an operating frequency of 10 MHz and a memory depth of 8 M (2$^{23}$) instructions, both easily scalable. Successive experimental sequences can be stacked with no dead time and synchronized with external events at any instructions. Two or more units can be cascaded and synchronized to a common clock, a feature useful to operate large experimental setups in a modular way.

physics.atom-ph↗

arXiv2019

Loading and Cooling in an Optical Trap via Hyperfine Dark States

We present a novel optical cooling scheme that relies on hyperfine dark states to enhance loading and cooling atoms inside deep optical dipole traps. We demonstrate a seven-fold increase in the number of atoms loaded in the conservative potential with strongly shifted excited states. In addition, we use the energy selective dark-state to efficiently cool the atoms trapped inside the conservative potential rapidly and without losses. Our findings open the door to optically assisted cooling of trapped atoms and molecules which lack the closed cycling transitions normally needed to achieve low temperatures and the high initial densities required for evaporative cooling.

physics.atom-ph↗

arXiv2018

BEC array in a Malleable Optical Trap formed in a Traveling Wave Cavity

Although quantum degenerate gases of neutral atoms have shown remarkable progress in the study of many body quantum physics, condensed matter physics, precision measurements, and quantum information processing, experimental progress is needed in order to reach their full potential in these fields. More complex spatial geometries as well as novel methods for engineering interesting interactions are needed. Here we demonstrate a novel experimental platform for the realization of quantum degenerate gases with a wide range of tune-ability in the spatial geometries experienced by the atoms and with the possibility of non-trivial long-range interactions both within and between multiple 87Rb Bose-Einstein condensates (BECs). We explore the use of a large mode-volume bow-tie ring cavity resonant at two wavelengths, $λ$ =1560 and 780 nm, for the creation of multiple BECs within a Malleable optical trap which also possesses the ability of photon-mediated long-range interactions. By exciting diverse transverse modes at 1560 nm, we can realize many optical trapping geometries which can open the door to spatial quantum state engineering with cavity-coupled BECs. As representative examples we realize a BEC in the fundamental TEM00 and a double BEC in the TEM01 mode of the cavity. By controlling the power between the fundamental and the higher transverse cavity mode, splitting and merging of cold thermal atomic ensemble is shown as well as the potential of creating more complex trapping geometries such as uniform potentials. Due to the double resonance of the cavity, we can envision a quantum network of BECs coupled via cavity-mediated interactions in non-trivial geometries.

cond-mat.quant-gas↗

arXiv2006

Axicon Lens for Coherent Matter Waves

We have realized a conical matter wave lens. The repulsive potential of a focused laser beam was used to launch a Bose-Einstein condensate into a radially expanding wavepacket whose perfect ring shape was ensured by energy conservation. In spite of significant interactions between atoms, the spatial and velocity widths of the ring along its radial dimension remained extremely narrow, as also confirmed by numerical simulations. Our results open the possibility for cylindrical atom optics without the perturbing effect of mean-field interactions.

cond-mat.other↗

arXiv2006

Dynamics of rotating Bose-Einstein condensates probed by Bragg scattering

Gaseous Bose-Einstein condensates (BECs) have become an important test bed for studying the dynamics of quantized vortices. In this work we use two-photon Doppler sensitive Bragg scattering to study the rotation of sodium BECs. We analyze the microscopic flow field and present laboratory measurements of the coarse-grained velocity profile. Unlike time-of-flight imaging, Bragg scattering is sensitive to the direction of rotation and therefore to the phase of the condensate. In addition, we have non-destructively probed the vortex flow field using a sequence of two Bragg pulses.

cond-mat.other↗

arXiv2005

Bragg Spectroscopy of Vortex Lattices in Bose-Einstein condensates

We have measured the velocity field of a vortex lattice within a sodium Bose-Einstein condensate using Bragg scattering. The phase gradient of the macroscopic wavefunction was mapped into the spatial structure of the diffracted atom cloud, allowing for single shot measurement of the rotation parameters. A combination of spectral and spatial information yields a complete description of the superfluid flow, coarse-grained over the lattice structure, including direct and independent measurements of the rate and sense of rotation. Signatures of the microscopic quantum rotation have also been observed.

cond-mat.other↗

arXiv2005

Metastable Bose-Einstein Condensate in a Linear Potential

We have created a Bose-Einstein condensate whose spin orientation is metastable. Condensates were transferred into a quadrupole magnetic trap, where Majorana transitions limited the lifetime to a few hundred milliseconds, about 30 times the trapping period. Atoms held in the trap frequently displayed a ring-shaped time-of-flight distribution. We speculate that such a ring could be either a quantized vortex or a feature of the Majorana loss dynamics in the quantum regime.

cond-mat.other↗

arXiv2004

An Optically Plugged Quadrupole Trap for Bose-Einstein Condensates

We created sodium Bose-Einstein condensates in an optically plugged quadrupole magnetic trap (OPT). A focused, 532nm laser beam repelled atoms from the coil center where Majorana loss is significant. We produced condensates of up to $3 \times 10^7$ atoms, a factor of 60 improvement over previous work [1], a number comparable to the best all-magnetic traps, and transferred up to $9 \times 10^6$ atoms into a purely optical trap. Due to the tight axial confinement and azimuthal symmetry of the quadrupole coils, the OPT shows promise for creating Bose-Einstein condensates in a ring geometry.

cond-mat.other↗

arXiv1999

Entangled state quantum cryptography: Eavesdropping on the Ekert protocol

Using polarization-entangled photons from spontaneous parametric downconversion, we have implemented Ekert's quantum cryptography protocol. The near-perfect correlations of the photons allow the sharing of a secret key between two parties. The presence of an eavesdropper is continually checked by measuring Bell's inequalities. We investigated several possible eavesdropper strategies, including pseudo-quantum non-demolition measurements. In all cases, the eavesdropper's presence was readily apparent. We discuss a procedure to increase her detectability.

quant-ph↗