arXiv subjects

G. Sampath

Publications and source records attributed to G. Sampath.

3 recordsLinked to original sources

arXiv2014

A Tandem Cell for Nanopore-based DNA Sequencing with Exonuclease

A tandem cell is proposed for DNA sequencing in which an exonuclease enzyme cleaves bases (mononucleotides) from a strand of DNA for identification inside a nanopore. It has two nanopores and three compartments with the structure [cis1, upstream nanopore (UNP), trans1=cis2, downstream nanopore (DNP), trans2]. The exonuclease is attached to the exit side of UNP in trans1/cis2. A cleaved base cannot regress into cis1 because of the remaining DNA strand in UNP. A profiled electric field over DNP with positive and negative components slows down base translocation through DNP. The proposed structure is modeled with a Fokker-Planck equation and a piecewise solution presented. Results from the model indicate that with probability approaching 1 bases enter DNP in their natural order, are detected without any loss, and do not regress into DNP after progressing into trans2. Sequencing efficiency with a tandem cell would then be determined solely by the level of discrimination among the base types inside DNP.

q-bio.BM↗

arXiv2005

A proposal for a two-slit experiment with a mirror

Summary. A modified version of the two-slit experiment is proposed in which the moveable detector/counter used to obtain the fringe distribution by counting single photons at different positions on the screen plane is replaced with a mirror positioned at an angle to the screen plane. A single photon arriving at the mirror through one of the slits is reflected at one of two angles along one of two divergent paths. It is then detected by one of two detectors, one on each of the paths, for different positions of the mirror on the screen plane. This modification results in the ability to generate which way information based on the path taken by the reflected photon as well as the distribution of photon counts on the screen plane, one for each slit. Since the photon does not experience any change other than the reflection at the mirror the question whether fringes are also present because of a priori interference effects when no mirror is present can be answered by examining the two a posteriori distributions. Three possible outcomes are considered and explanations proposed for them. The experiment is shown to be feasible with existing technology and can be performed in most physics laboratories.

quant-ph↗

arXiv2001

A quantum computing scheme for the Hamiltonian path problem

A quantum computing scheme that uses a single photon and multiple-slit gratings is suggested for the Hamiltonian path problem on a simple graph G of N vertices. The photon is input to an N-slit grating followed by an N x N matrix of `processing units'. A unit consists of a delay line followed by a grating with k slits (0 < k < N) whose outputs are directed to k units in the next row in a manner determined by the adjacency matrix of G. There is a one-to-one mapping between paths of length N-1 in the graph and physical paths through the matrix. The photon's path is a superposition of all these physical paths. The time taken by the photon along a physical path corresponding to a Hamiltonian path in G is a fixed value equal to the sum of N distinct delays, and is different from the time along any other path. The graph is Hamiltonian if any one of N detectors placed in the output of the N units in row N detects the photon at this fixed time.

quant-ph↗