## Quantum Computing

### Coherent control of decoherence

Control of molecular reaction directs vibronically excited molecular systems into specific reaction pathways.

Failure through such molecular control through laser selective excitation arises from decoherence and dephasing of coherence. Minimizing decoherence is also an important challenge towards realizing quantum computing and quantum information. Typical molecular vibrations occur in picoseconds. So it is important to have control parameters in femtoseconds. Population transfer in molecules involves multiple states besides the radiative coupled two labels which undergo quantum interferences resulting in decoherences. Coupling to the non radiative channels can however be minimized to robustly controlled decoherence through destructive quantum interference between the multiple excitation pathways. Thus a useful quantification of controllability can be identified in terms of two label of character in a multilevel system through density matrix evaluation of coherent character of quantum states. Only a synergy of molecular dynamics and spatio-temporal control of molecules embodies the future of quantum information and computing. It turns out that the very oddly separated areas become connected. Because of that Quantum computing on very odd end gets connected because there also you need 100% controllability as well as 100% both spatial and temporal controllability. And we want to do with optics only. Now light has many more implications. You can actually encode light by informing, putting in data. So there are some data communication issues also which we can bring in, which is generally not what we basically work on. Our data communication only stops at the point that we have informed the molecule what to do. We are not using that as an electrical data communication scheme any more. We had started that at some point of time but now we have moved into more into informing the molecule business. Now the molecule is supposed to take it further and that is the quantum aspect. Sometimes we are not interested in to see the take it further part. We are very happy with when we inform the molecule and get a response from it.

Some of our work includes [1,2,3,4]

## Publications

1. Quantum Distributed Computing Applied to Grover’s Search Algorithm. D. Goswami, in Computing with New Resources: Essays Dedicated to Jozef Gruska on the Occasion of His 80th Birthday, C. S. Calude, R. Freivalds, and I. Kazuo, eds., Lecture Notes in Computer Science (Springer International Publishing, 2014), pp. 192–199

Abstract: Grover’s Algorithm finds a unique element in an unsorted stock of NNN-elements in N−−√N\sqrt{N} queries through quantum search. A single-query solution can also be designed, but with an overhead of Nlog2NNlog2⁡NN\log _2 N steps to prepare and post process the query, which is worse than the classical N/2N/2N/2 queries. We show here that by distributing the computing load on a set of quantum computers, we achieve better information theoretic bounds and relaxed space scaling. Howsoever small one quantum computing node is, by virtue of networking and sharing of data, we can virtually work with a sufficiently large qubit space.

 BibTeX: @incollection{goswamiQuantumDistributedComputing2014,
langid = {english},
location = {{Cham}},
title = {Quantum {{Distributed Computing Applied}} to {{Grover}}’s {{Search Algorithm}}},
isbn = {978-3-319-13350-8},
url = {https://my.pcloud.com/publink/show?code=XZMGxr7Zz6GcnHs4eDHBBtjbl9pyEXfvUXhV},
booktitle = {Computing with {{New Resources}}: {{Essays Dedicated}} to {{Jozef Gruska}} on the {{Occasion}} of {{His}} 80th {{Birthday}}},
series = {Lecture {{Notes}} in {{Computer Science}}},
publisher = {{Springer International Publishing}},
urldate = {2019-08-02},
date = {2014},
pages = {192-199},
author = {Goswami, Debabrata},
editor = {Calude, Cristian S. and Freivalds, Rūsiņš and Kazuo, Iwama}
}

2. Quantum Algorithm to Solve a Maze: Converting the Maze Problem into a Search Problem. N. Kumar and D. Goswami, (2013)

Abstract: We propose a different methodology towards approaching a Maze problem. We convert the problem into a Quantum Search Problem (QSP), and its solutions are sought for using the iterative Grover’s Search Algorithm. Though the category of mazes we are looking at are of the NP complete class, we have redirected such a NP complete problem into a QSP. Our solution deals with two dimensional perfect mazes with no closed loops. We encode all possible individual paths from the starting point of the maze into a quantum register. A quantum fitness operator applied on the register encodes each individual with its fitness value. We propose an oracle design which marks all the individuals above a certain fitness value and use the Grover search algorithm to find one of the marked states. Iterating over this method, we approach towards the optimum solution.

 BibTeX: @article{kumarQuantumAlgorithmSolve2013,
archiveprefix = {arXiv},
eprinttype = {arxiv},
eprint = {1312.4116},
primaryclass = {quant-ph},
title = {Quantum {{Algorithm}} to {{Solve}} a {{Maze}}: {{Converting}} the {{Maze Problem}} into a {{Search Problem}}},
url = {http://arxiv.org/abs/1312.4116},
shorttitle = {Quantum {{Algorithm}} to {{Solve}} a {{Maze}}},
urldate = {2019-08-02},
date = {2013-12-15},
author = {Kumar, Niraj and Goswami, Debabrata}
}

3. Computing with New Resources: Essays Dedicated to Jozef Gruska on the Occasion of His 80th Birthday. C. S. Calude, R. Freivalds, and I. Kazuo, (Springer, 2014)

Abstract: Professor Jozef Gruska is a well known computer scientist for his many and broad results. He was the father of theoretical computer science research in Czechoslovakia and among the first Slovak programmers in the early 1960s. Jozef Gruska introduced the descriptional complexity of grammars, automata, and languages, and is one of the pioneers of parallel (systolic) automata. His other main research interests include parallel systems and automata, as well as quantum information processing, transmission, and cryptography. He is co-founder of four regular series of conferences in informatics and two in quantum information processing and the Founding Chair (1989-96) of the IFIP Specialist Group on Foundations of Computer Science.

 BibTeX: @book{caludeComputingNewResources2014,
langid = {english},
title = {Computing with {{New Resources}}: {{Essays Dedicated}} to {{Jozef Gruska}} on the {{Occasion}} of {{His}} 80th {{Birthday}}},
isbn = {978-3-319-13350-8},
shorttitle = {Computing with {{New Resources}}},
pagetotal = {486},
publisher = {{Springer}},
date = {2014-12-09},
author = {Calude, Cristian S. and Freivalds, Rūsiņš and Kazuo, Iwama},
eprinttype = {googlebooks},
eprint = {QLLLBQAAQBAJ}
}

4. Quantum Distributed Computing with Shaped Laser Pulses. R. Goswami and D. Goswami, in 13th International Conference on Fiber Optics and Photonics (OSA, 2016), p. W4C.3

Abstract: Shaped laser pulses can control decoherence under quantum adiabatic method of logic operations to result in a possible scalable quantum computer by distributing the computing load on a set of optically adiabatic quantum computing nodes.

 BibTeX: @inproceedings{goswamiQuantumDistributedComputing2016,
langid = {english},
location = {{Kanpur}},
title = {Quantum {{Distributed Computing}} with {{Shaped Laser Pulses}}},
isbn = {978-1-943580-22-4},
doi = {10/gf5mrr},
eventtitle = {International {{Conference}} on {{Fibre Optics}} and {{Photonics}}},
booktitle = {13th {{International Conference}} on {{Fiber Optics}} and {{Photonics}}},
publisher = {{OSA}},
date = {2016},
pages = {W4C.3},
author = {Goswami, Rohit and Goswami, Debabrata}
}