Papers by Asiri Nanayakkara
arXiv (Cornell University), Mar 22, 2018
In this study we show a way of achieving the reverse evolution of-dimensional quantum walks by in... more In this study we show a way of achieving the reverse evolution of-dimensional quantum walks by introducing interventions on the coin degree of freedom during the forward progression of the coinwalker system. Only a single intervention is required to reverse a quantum walker on a line to its initial positon and the number of interventions increases with the dimensionality of the walk. We present an analytical treatment to prove these results. This reversion scheme can be used to generate periodic bounded quantum walks and to control the locations where particle can be found with highest probability. From the point of view of quantum computations and simulations, this scheme could be useful in resetting quantum operations and implementing certain quantum gates.
arXiv (Cornell University), Mar 22, 2018
In this study we show a way of achieving the reverse evolution of-dimensional quantum walks by in... more In this study we show a way of achieving the reverse evolution of-dimensional quantum walks by introducing interventions on the coin degree of freedom during the forward progression of the coinwalker system. Only a single intervention is required to reverse a quantum walker on a line to its initial positon and the number of interventions increases with the dimensionality of the walk. We present an analytical treatment to prove these results. This reversion scheme can be used to generate periodic bounded quantum walks and to control the locations where particle can be found with highest probability. From the point of view of quantum computations and simulations, this scheme could be useful in resetting quantum operations and implementing certain quantum gates.
Physical Review A, 2022
The study of recurrences and revivals in quantum systems has attracted a great deal of interest b... more The study of recurrences and revivals in quantum systems has attracted a great deal of interest because of its importance in the control of quantum systems and its potential use in developing new technologies. In this work, we introduce a protocol to induce full-state revivals in a huge class of quantum walks on a d-dimensional lattice governed by a c-dimensional coin system. The protocol requires two repeated interventions in the coin degree of freedom. We also present a characterization of the walks that admits such a protocol. Moreover, we modify the quantity known as Pólya number, typically used in the study of recurrences in classical random walks and quantum walks, to create a witness of the first revival of the walk.
Physical Review A, 2022
The study of recurrences and revivals in quantum systems has attracted a great deal of interest b... more The study of recurrences and revivals in quantum systems has attracted a great deal of interest because of its importance in the control of quantum systems and its potential use in developing new technologies. In this work, we introduce a protocol to induce full-state revivals in a huge class of quantum walks on a d-dimensional lattice governed by a c-dimensional coin system. The protocol requires two repeated interventions in the coin degree of freedom. We also present a characterization of the walks that admits such a protocol. Moreover, we modify the quantity known as Pólya number, typically used in the study of recurrences in classical random walks and quantum walks, to create a witness of the first revival of the walk.
We introduce an analytically treatable spin decoherence model for quantum walk on a line that yie... more We introduce an analytically treatable spin decoherence model for quantum walk on a line that yields the exact position probability distribution of an unbiased classical random walk at all-time scales. This spin decoherence model depicts a quantum channel in which simultaneous bit and phase flip operator is applied at random on the coin state. Based on this result we claim that there exist certain quantum channels that can produce exact classical statistical properties for a given one-dimensional quantum walk. Moreover, from the perspective of quantum computing, decoherence model introduced in this study may have useful algorithmic applications when it is applied on quantum walks with non-local initial states.
We introduce an analytically treatable spin decoherence model for quantum walk on a line that yie... more We introduce an analytically treatable spin decoherence model for quantum walk on a line that yields the exact position probability distribution of an unbiased classical random walk at all-time scales. This spin decoherence model depicts a quantum channel in which simultaneous bit and phase flip operator is applied at random on the coin state. Based on this result we claim that there exist certain quantum channels that can produce exact classical statistical properties for a given one-dimensional quantum walk. Moreover, from the perspective of quantum computing, decoherence model introduced in this study may have useful algorithmic applications when it is applied on quantum walks with non-local initial states.
Differentiation of signals generated by eye blinks and mouth clenching in a portable brain computer interface system
2017 IEEE International Conference on Industrial and Information Systems (ICIIS), 2017
Patients who are completely paralyzed cannot move their muscles according to their intentions. Ho... more Patients who are completely paralyzed cannot move their muscles according to their intentions. However, the majority of partially paralyzed individuals can move some of their muscles and eyes voluntarily. The monitoring of electrical activity produced by muscle movements are known as Electromyography (EMG) and the same due to eye blinks and eye movements are known as an electrooculography (EOG). Furthermore, the signals coming from EMG and EOG activities are stronger than same produced by Electroencephalography (EEG). Therefore, it is useful to have a Brain computer interface system (BCI) which operates on EMG and EOG activities in addition to EEG. The objective of this study is to investigate the distinguishability of various signals produce by EMG and EOG activities and thereby utilizing them for constructing an effective BCI system which operates according to the user intentions. Three types of EMG/EOG signals are investigated in this study. They are single eye blink, double eye blink and mouth clenching. We have developed an efficient procedure to differentiate these three activities in real time and implemented it using MATLAB. Furthermore, this efficient implementation is embedded in our Brain Computer Interface system called GINIE. As a result, we are able to control external lights, television sets and computer mouse 100% accurately and efficiently only using three signal types mentioned above. Also the EEG processing techniques of GINIE is used to generate speech commands according to the intention of the user. These features of GINIE was successfully demonstrated at the "Annual review session of National Institute of Fundamental Studies" held in March 2017.
Investigation of Light Intensity of Single Bubble Sonoluminescence (SBSL) in Water and Fluorescein Sodium Solution
Sonoluminescence is the phenomenon of mysterious conversion of acoustic energy into pulses of lig... more Sonoluminescence is the phenomenon of mysterious conversion of acoustic energy into pulses of light. The spectrum of SBSL in water has been observed in the range of UV to IR. However, water strongly absorbs photons of wavelengths less than 200 nm and therefore, spectrum of SBSL below 200 nm has not been detected yet. In this study, the intensity of light produced by Single Bubble Sonoluminescence (SBSL) in water and Fluorescein Sodium solution 0.1 mM was measured. By adding Fluorescein Sodium to water, the intensity of SBSL was increased by 34% - 94% depending on the ambient temperature indicating that considerable amount of both visible and UV light get absorbed by water in the flask. As a result, SBSL spectrum obtained directly from water consists only a part of the full spectrum. Temperature dependence of the intensity of SBSL light was determined for deionized distilled water and water with Fluorescein Sodium.
Differentiation of signals generated by eye blinks and mouth clenching in a portable brain computer interface system
2017 IEEE International Conference on Industrial and Information Systems (ICIIS), 2017
Patients who are completely paralyzed cannot move their muscles according to their intentions. Ho... more Patients who are completely paralyzed cannot move their muscles according to their intentions. However, the majority of partially paralyzed individuals can move some of their muscles and eyes voluntarily. The monitoring of electrical activity produced by muscle movements are known as Electromyography (EMG) and the same due to eye blinks and eye movements are known as an electrooculography (EOG). Furthermore, the signals coming from EMG and EOG activities are stronger than same produced by Electroencephalography (EEG). Therefore, it is useful to have a Brain computer interface system (BCI) which operates on EMG and EOG activities in addition to EEG. The objective of this study is to investigate the distinguishability of various signals produce by EMG and EOG activities and thereby utilizing them for constructing an effective BCI system which operates according to the user intentions. Three types of EMG/EOG signals are investigated in this study. They are single eye blink, double eye blink and mouth clenching. We have developed an efficient procedure to differentiate these three activities in real time and implemented it using MATLAB. Furthermore, this efficient implementation is embedded in our Brain Computer Interface system called GINIE. As a result, we are able to control external lights, television sets and computer mouse 100% accurately and efficiently only using three signal types mentioned above. Also the EEG processing techniques of GINIE is used to generate speech commands according to the intention of the user. These features of GINIE was successfully demonstrated at the "Annual review session of National Institute of Fundamental Studies" held in March 2017.
Investigation of Light Intensity of Single Bubble Sonoluminescence (SBSL) in Water and Fluorescein Sodium Solution
Sonoluminescence is the phenomenon of mysterious conversion of acoustic energy into pulses of lig... more Sonoluminescence is the phenomenon of mysterious conversion of acoustic energy into pulses of light. The spectrum of SBSL in water has been observed in the range of UV to IR. However, water strongly absorbs photons of wavelengths less than 200 nm and therefore, spectrum of SBSL below 200 nm has not been detected yet. In this study, the intensity of light produced by Single Bubble Sonoluminescence (SBSL) in water and Fluorescein Sodium solution 0.1 mM was measured. By adding Fluorescein Sodium to water, the intensity of SBSL was increased by 34% - 94% depending on the ambient temperature indicating that considerable amount of both visible and UV light get absorbed by water in the flask. As a result, SBSL spectrum obtained directly from water consists only a part of the full spectrum. Temperature dependence of the intensity of SBSL light was determined for deionized distilled water and water with Fluorescein Sodium.
A low-cost, portable biopotential monitoring system to study electrical activities of the human brain and the body
European Journal of Physics, 2020
A portable, low-cost, all-in-one biopotential monitoring system that can be used for demonstratin... more A portable, low-cost, all-in-one biopotential monitoring system that can be used for demonstrating the basic characteristics of electrical activities of the human brain and body for undergraduate physics students is described. The monitoring system consists of a wireless biopotential amplifier, an electrode cap and a software interface. Some of the biopotential activities recorded from the monitoring system, together with theoretical explanations associated with them are presented. Experimentation with the system will provide students with an opportunity to verify the theories involved in biopotential activities. The construction of the system can also be an interesting project for undergraduate students and it exposes them to instrument construction and troubleshooting techniques.
A low-cost, portable biopotential monitoring system to study electrical activities of the human brain and the body
European Journal of Physics, 2020
A portable, low-cost, all-in-one biopotential monitoring system that can be used for demonstratin... more A portable, low-cost, all-in-one biopotential monitoring system that can be used for demonstrating the basic characteristics of electrical activities of the human brain and body for undergraduate physics students is described. The monitoring system consists of a wireless biopotential amplifier, an electrode cap and a software interface. Some of the biopotential activities recorded from the monitoring system, together with theoretical explanations associated with them are presented. Experimentation with the system will provide students with an opportunity to verify the theories involved in biopotential activities. The construction of the system can also be an interesting project for undergraduate students and it exposes them to instrument construction and troubleshooting techniques.
Physica Scripta, 2018
Full state revivals in a quantum walk can be viewed as returning of the walker to the initial qua... more Full state revivals in a quantum walk can be viewed as returning of the walker to the initial quantum state in a periodic fashion during the propagation of the walk. In this paper we show that for any given number of spatial dimensions, a coin operator can be constructed to generate a quantum walk having full revivals with any desired period. From the point of view of quantum computation and simulations, these coin operators can be useful in implementing quantum walks which oscillate between any two states with a finite periodicity.
Physica Scripta, 2018
Full state revivals in a quantum walk can be viewed as returning of the walker to the initial qua... more Full state revivals in a quantum walk can be viewed as returning of the walker to the initial quantum state in a periodic fashion during the propagation of the walk. In this paper we show that for any given number of spatial dimensions, a coin operator can be constructed to generate a quantum walk having full revivals with any desired period. From the point of view of quantum computation and simulations, these coin operators can be useful in implementing quantum walks which oscillate between any two states with a finite periodicity.
Proceedings of the National Academy of Sciences, India Section A: Physical Sciences, 2018
A new way of constructing SUSY partner potentials with PT symmetry is proposed. In this construct... more A new way of constructing SUSY partner potentials with PT symmetry is proposed. In this construction, PT symmetric superpotentials generate PT symmetric SUSY partners and supercharges that satisfy commutator-anti-commutator relations of close superalgebra SL(1/1). Conversely, every PT symmetric Hamiltonian having zero or non zero ground state energy can be generated using PT symmetric superpotentials. Further, superpotentials having separate P and T symmetries can generate strictly isospectral SUSY partners if the wedge of integration can accommodate two asymptotically opposite quantization contours.
Proceedings of the National Academy of Sciences, India Section A: Physical Sciences, 2018
A new way of constructing SUSY partner potentials with PT symmetry is proposed. In this construct... more A new way of constructing SUSY partner potentials with PT symmetry is proposed. In this construction, PT symmetric superpotentials generate PT symmetric SUSY partners and supercharges that satisfy commutator-anti-commutator relations of close superalgebra SL(1/1). Conversely, every PT symmetric Hamiltonian having zero or non zero ground state energy can be generated using PT symmetric superpotentials. Further, superpotentials having separate P and T symmetries can generate strictly isospectral SUSY partners if the wedge of integration can accommodate two asymptotically opposite quantization contours.
Journal of the National Science Foundation of Sri Lanka, 2009
Both real and complex semiclassical eigen energies of two dimensional non-Hermitian Hamiltonian s... more Both real and complex semiclassical eigen energies of two dimensional non-Hermitian Hamiltonian systems are obtained by classical (Lie transform) perturbation theory requiring the action variables I 1 and I 2 to satisfy the quantization condition I 1 =(n 1 +(1/2))ℏ and I 2 =(n 2 +(1/2))ℏ respectively where n 1 , n 2 are integers. Classical perturbation theory with Lie transform makes classical trajectories, which are non-periodic or non-quasi-periodic, periodic. It was observed that this method produces accurate eigen energies even when classical trajectories are not periodic or quasi-periodic. Eigen energies obtained by classical perturbation theory are compared with the same, determined by Rayleigh-Schroedinger perturbation theory
Journal of the National Science Foundation of Sri Lanka, 2009
Both real and complex semiclassical eigen energies of two dimensional non-Hermitian Hamiltonian s... more Both real and complex semiclassical eigen energies of two dimensional non-Hermitian Hamiltonian systems are obtained by classical (Lie transform) perturbation theory requiring the action variables I 1 and I 2 to satisfy the quantization condition I 1 =(n 1 +(1/2))ℏ and I 2 =(n 2 +(1/2))ℏ respectively where n 1 , n 2 are integers. Classical perturbation theory with Lie transform makes classical trajectories, which are non-periodic or non-quasi-periodic, periodic. It was observed that this method produces accurate eigen energies even when classical trajectories are not periodic or quasi-periodic. Eigen energies obtained by classical perturbation theory are compared with the same, determined by Rayleigh-Schroedinger perturbation theory
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Papers by Asiri Nanayakkara