arXiv subjects

Amandeep Singh

Publications and source records attributed to Amandeep Singh.

28 records · Page 2Linked to original sources

arXiv2019

Experimental Detection of Qubit-Ququart Pseudo-Bound Entanglement using Three Nuclear Spins

In this work, we experimentally created and characterized a class of qubit-ququart PPT (positive under partial transpose) entangled states using three nuclear spins on an nuclear magnetic resonance (NMR) quantum information processor. Entanglement detection and characterization for systems with a Hilbert space dimension $\ge 2 \otimes 3$ is nontrivial since there are states in such systems which are both PPT as well as entangled. The experimental detection scheme that we devised for the detection of qubit-ququart PPT entanglement was based on the measurement of three Pauli operators with high precision, and is a key ingredient of the protocol in detecting entanglement. The family of PPT-entangled states considered in the current study are incoherent mixtures of five pure states. All the five states were prepared with high fidelities and the resulting PPT entangled states were prepared with mean fidelity $\ge 0.95$. The entanglement thus detected was validated by carrying out full quantum state tomography (QST).

quant-ph↗

arXiv2018

Experimentally identifying the entanglement class of pure tripartite states

We use concurrence as an entanglement measure and experimentally demonstrate the entanglement classification of arbitrary three-qubit pure states on a nuclear magnetic resonance (NMR) quantum information processor. Computing the concurrence experimentally under three different bipartitions, for an arbitrary three-qubit pure state, reveals the entanglement class of the state. The experiment involves measuring the expectation values of Pauli operators. This was achieved by mapping the desired expectation values onto the local $z$ magnetization of a single qubit. We tested the entanglement classification protocol on twenty seven different generic states and successfully detected their entanglement class. Full quantum state tomography was performed to construct experimental tomographs of each state and negativity was calculated from them, to validate the experimental results.

quant-ph↗

arXiv2018

Experimental Classification of Entanglement in Arbitrary Three-Qubit States on an NMR Quantum Information Processor

We undertake experimental detection of the entanglement present in arbitrary three-qubit pure quantum states on an NMR quantum information processor. Measurements of only four observables suffice to experimentally differentiate between the six classes of states which are inequivalent under stochastic local operation and classical communication (SLOCC). The experimental realization is achieved by mapping the desired observables onto Pauli $z$-operators of a single qubit, which is directly amenable to measurement. The detection scheme is applied to known entangled states as well as to states randomly generated using a generic scheme that can construct all possible three-qubit states. The results are substantiated via direct full quantum state tomography as well as via negativity calculations and the comparison suggests that the protocol is indeed successful in detecting tripartite entanglement without requiring any {\it a priori} information about the states.

quant-ph↗

arXiv2018

Experimental demonstration of selective quantum process tomography on an NMR quantum information processor

We present the first NMR implementation of a scheme for selective and efficient quantum process tomography without ancilla. We generalize this scheme such that it can be implemented efficiently using only a set of measurements involving product operators. The method allows us to estimate any element of the quantum process matrix to a desired precision, provided a set of quantum states can be prepared efficiently. Our modified technique requires fewer experimental resources as compared to the standard implementation of selective and efficient quantum process tomography, as it exploits the special nature of NMR measurements to allow us to compute specific elements of the process matrix by a restrictive set of sub-system measurements.To demonstrate the efficacy of our scheme, we experimentally tomograph the processes corresponding to `no operation', a controlled-NOT (CNOT), and a controlled-Hadamard gate on a two-qubit NMR quantum information processor, with high fidelities.

quant-ph↗

arXiv2017

Witnessing nonclassical correlations via a single-shot experiment on an ensemble of spins using NMR

A bipartite quantum system in a mixed state can exhibit nonclassical correlations, which can go beyond quantum entanglement. While quantum discord is the standard measure of quantifying such general quantum correlations, the nonclassicality can be determined by simpler means via the measurement of witness operators. We experimentally construct a positive map to witness nonclassicality of two qubits in an NMR system. The map can be decomposed so that a single run of an experiment on an ensemble of spins suffices to detect the nonclassicality in the state, if present. We let the state evolve in time and use the map to detect nonclassicality as a function of time. To evaluate the efficacy of the witness operator as a means to detect nonclassicality, we measure quantum discord by performing full quantum state tomography at each time point and obtained a fairly good match between the two methods.

quant-ph↗

arXiv2016

Entanglement detection on an NMR quantum information processor using random local measurements

Random local measurements have recently been proposed to construct entanglement witnesses and thereby detect the presence of bipartite entanglement. We experimentally demonstrate the efficacy of one such scheme on a two-qubit NMR quantum information processor. We show that a set of three random local measurements suffices to detect the entanglement of a general two-qubit state. We experimentally generate states with different amounts of entanglement, and show that the scheme is able to clearly witness entanglement. We perform complete quantum state tomography for each state and compute state fidelity to validate our results. Further, we extend previous results and perform a simulation using random local measurements to optimally detect bipartite entanglement in a hybrid system of $2\otimes 3$ dimensionality.

quant-ph↗

arXiv2015

Role of different scattering mechanisms on the temperature dependence of transport in graphene

Detailed experimental and theoretical studies of the temperature dependence of the effect of different scattering mechanisms on electrical transport properties of graphene devices are presented. We find that for high mobility devices the transport properties are mainly governed by completely screened short range impurity scattering. On the other hand, for the low mobility devices transport properties are determined by both types of scattering potentials - long range due to ionized impurities and short range due to completely screened charged impurities. The results could be explained in the framework of Boltzmann transport equations involving the two independent scattering mechanisms.

cond-mat.mes-hall↗

arXiv2014

Semi-active Suspension Control using Modern Methodology: Comprehensive Comparison Study

Semi-active suspensions have drawn particular attention due to their superior performance over the other types of suspensions. One of their advantages is that their damping coefficient can be controlled without the need for any external source of power. In this study, three control approaches are implemented on a quarter-car model using MATLAB/Simulink. The investigated control methodologies are Acceleration Driven Damper, Power Driven Damper, and H_infinity Robust Control. The three controllers are known as comfort-oriented approaches. H_infinity Robust Control is an advanced method that guarantees transient performance and rejects external disturbances. It is shown that H_infinity with the proposed modification, has the best performance although its relatively high cost of computation could be potentially considered as a drawback.

eess.SY↗

arXiv2014

Design and Implementation of Bit Transition Counter

In today VLSI system design, power consumption is gaining more attention as compared to performance and area. This is due to battery life in portable devices and operating frequency of the design. Power consumption mainly consists of static power, dynamic power, leakage power and short circuit power. Dynamic power is dominant among all which depends on many factors viz. power supply, load capacitance and frequency. Switching activity also affects dynamic power consumption of bus which is determined by calculating the number of bit transitions on bus. The purpose of this paper is to design a bit transition counter which can be used to calculate the switching activity of the circuit nodes. The novel feature is that it can be inserted at any node of the circuit, thus helpful for calculating power consumption of bus.

cs.AR↗

arXiv2012

Microcontroller Based Testing of Digital IP-Core

Testing core based System on Chip is a challenge for the test engineers. To test the complete SOC at one time with maximum fault coverage, test engineers prefer to test each IP-core separately. At speed testing using external testers is more expensive because of gigahertz processor. The purpose of this paper is to develop cost efficient and flexible test methodology for testing digital IP-cores . The prominent feature of the approach is to use microcontroller to test IP-core. The novel feature is that there is no need of test pattern generator and output response analyzer as microcontroller performs the function of both. This approach has various advantages such as at speed testing, low cost, less area overhead and greater flexibility since most of the testing process is based on software.

cs.AR↗