arXiv subjects

Subrata Saha

Publications and source records attributed to Subrata Saha.

5 recordsLinked to original sources

arXiv2020

MSPP: A Highly Efficient and Scalable Algorithm for Mining Similar Pairs of Points

The closest pair of points problem or closest pair problem (CPP) is an important problem in computational geometry where we have to find a pair of points from a set of points in metric space with the smallest distance between them. This problem arises in a number of applications, such as but not limited to clustering, graph partitioning, image processing, patterns identification, and intrusion detection. For example, in air-traffic control, we must monitor aircrafts that come too close together, since this may potentially indicate a possible collision. Numerous algorithms have been presented for solving the CPP. The algorithms that are employed in practice have a worst case quadratic run time complexity. In this article we present an elegant approximation algorithm for the CPP called MSPP: Mining Similar Pairs of Points. It is faster than currently best known algorithms while maintaining a very good accuracy. The proposed algorithm also detects a set of closely similar pairs of points in Euclidean and Pearson metric spaces and can be adapted in numerous real world applications, such as clustering, dimension reduction, constructing and analyzing gene/transcript co-expression network, among others.

cs.DS↗

arXiv2017

Optical cooling of interacting atoms in a tightly confined trap

In a recent paper, we have proposed a novel laser cooling scheme for reducing collisional energy of a pair of atoms by using photoassociative transitions. In that paper, we considered two atoms in free space, that is we have not considered the effects of trap on the cooling process. Here in this paper, we qualitatively discuss the possibility of extending this idea for Raman sideband cooling of a pair of interacting atoms trapped in Lamb-Dicke (LD) regime. Apart from cooling, our method may be important for manipulating on-site interaction of atoms in an optical lattice.

physics.atom-ph↗

arXiv2016

Manipulating nanoscale atom-atom interactions with cavity QED

We theoretically explore manipulation of interactions between excited and ground state atoms at nanoscale separations by cavity quantum electrodynamics (CQED). We develop an adiabatic molecular dressed state formalism and show that it is possible to generate Fano-Feshbach resonances between ground and long-lived excited-state atoms inside a cavity. The resonances are shown to arise due to non-adiabatic coupling near a pseudo-crossing between the dressed state potentials. We illustrate our results with a model study using fermionic $^{171}$Yb atoms in a two-modal cavity. Our study is important for manipulation of interatomic interactions at low energy by cavity field.

quant-ph↗

arXiv2016

Photoassociative cooling and trapping of a pair of interacting atoms

We show that it is possible to cool interacting pairs of atoms by a lin $\perp$ lin Sisyphus-like laser cooling scheme using counter-propagating photoassociation (PA) lasers. It is shown that the center-of-mass motion (c.m.) of atom pairs can be trapped in molecular spin-dependent periodic potentials generated by the lasers. The proposed scheme is most effective for narrow-line PA transitions. We illustrate this with numerical calculations using fermionic $^{171}$Yb atoms as an example.

physics.atm-clus↗

arXiv2014

Optical Feshbach resonances through a molecular dark state: Efficient manipulation of $p$-wave resonances in fermionic $^{171}$Yb atoms

In a recent experiment by Yamazaki {\it et al.} [Phys.Rev. A {\bf 87} 010704 (R) (2013) ], $p$-wave optical Feshbach resonance in fermionic $^{171}$Yb atoms using purely long-range molecular excited states has been demonstrated. We theoretically show that, if two purely long range excited states of $^{171}$Yb are coupled to the ground-state continuum of scattering states with two lasers, then it is possible to significantly suppress photoassociative atom loss by a dark resonance in the excited states. We present a general theoretical framework for creating a dark state in electronically excited molecular potential for the purpose of increasing the efficiency of an optical Feshbach resonance. This can be accomplished by properly adjusting the relative intensity, phase, polarizations and frequency detunings of two lasers. We present selective numerical results on atom loss spectra, $p$-wave elastic and inelastic scattering cross sections of $^{171}$Yb atoms to illustrate the effects of the molecular dark state on optical Feshbach resonance.

physics.atom-ph↗