Quantum Computers Could Excel In Modeling Chemical Reactions

Quantum computers would likely outperform conventional computers in simulating chemical reactions involving more than four atoms, according to scientists at Harvard University, the Massachusetts Institute of Technology, and Haverford College. Such improved ability to model and predict complex chemical reactions could revolutionize drug design and materials science, among other fields.

Writing in the Proceedings of the National Academy of Sciences, the researchers describe "software" that could simulate chemical reactions on quantum computers, an ultra-modern technology that relies on quantum mechanical phenomena, such as entanglement, interference, and superposition. Quantum computing has been heralded for its potential to solve certain types of problems that are impossible for conventional computers to crack.

"There is a fundamental problem with simulating quantum systems -- such as chemical reactions -- on conventional computers," says Alán Aspuru-Guzik, assistant professor of chemistry and chemical biology in Harvard's Faculty of Arts and Sciences. "As the size of a system grows, the computational resources required to simulate it grow exponentially. For example, it might take one day to simulate a reaction involving 10 atoms, two days for 11 atoms, four days for 12 atoms, eight days for 13 atoms, and so on. Before long, this would exhaust the world's computational power."

Unlike a conventional computer, Aspuru-Guzik and his colleagues say, a quantum computer could complete the steps necessary to simulate a chemical reaction in a time that doesn't increase exponentially with the reaction's complexity.

"Being able to predict the outcomes of chemical reactions would have tremendous practical applications," says Ivan Kassal, a graduate student in chemical physics at Harvard. "A lot of research in drug design, materials science, catalysis, and molecular biology is still done by trial and error. Having accurate predictions would change the way these types of science are done."

The researchers demonstrate in PNAS that quantum computers would need to attain a size of about 100 qubits -- which are to quantum computers as bits are to conventional computers -- to outperform current classical supercomputers at a chemical simulation.

"This is still far beyond current prototype quantum computers," Kassal says. "And although it might take millions of quantum elementary operations on a few hundred quantum bits, our work suggests that with quantum computers that are as fast as modern conventional computers, one could simulate in seconds a chemical reaction that would take a conventional computer years."

Rather than using binary bits labeled as "zero" and "one" to encode data, as in a conventional computer, quantum computing stores information in qubits, which can represent both "zero" and "one" simultaneously. When a quantum computer is put to work on a problem, it considers all possible answers by simultaneously arranging its qubits into every combination of "zeroes" and "ones."

Since one sequence of qubits can represent many different numbers, a quantum computer would make far fewer computations than a conventional one in solving some problems. After the computer's work is done, a measurement of its qubits provides the answer.

Aspuru-Guzik and Kassal's co-authors on the PNAS paper are Stephen P. Jordan of MIT, Peter J. Love of Haverford College, and Masoud Mohseni of Harvard. The work was sponsored by the Army Research Office and the Joyce and Zlatko Balokovic Scholarship.

http://www.sciencedaily.com/releases/2008/11/081120130601.htm

 

APPENDIX 2

Linking Devices

To introduce the subject	Many people think…, Some people say…, It may seem…, You’ve probably heard…, We take it for granted that…, The truth of the matter is…, It may seem	Some people say that Columbus discovered America.
To make contrasting points	although, yet, however, but, nevertheless, in spite of, despite, while, even if, even though, at the same time, on the other hand	Susan is very generous, however, she can be very bossy.
To list view points (sequencing)	firstly, in the first place, first of all, to start with, to begin with, secondly, thirdly, (so)then, next, finally, at the end, on top of that	First of all, describe this chart, then make a report.
To add more points on a topic	what is more, furthermore, also, apart from this/that, in addition to, moreover, besides, too, not to mention the fact that	Sue is a clever student. Furthermore/ Moreover/ What is more, she is a kind girl.
To join contrasting, negative ideas	neither …nor, neither/ nor, not …either	Neither crocodiles nor snakes are mammals.
To list advantages disadvantages	one /another /one other /a further /the main /the first /the greatest advantage /disadvantage of…	The greatest advantage of regular exercise is that it leads to a healthier lifestyle.
To express personal opinion	in my opinion/view, to my mind/way of thinking, personally I believe, it strikes me that, I feel very strongly that, I am inclined to believe that, it seems to me that, as far as I am concerned, personally, as for me	In my opinion /view department stores offer a greater selection of clothes than smaller boutiques.
To refer to other sources	according to, with reference to	According to his report neighbourhood watch scheme can work effectively.
To conclude	finally, lastly, above all, all in all, taking everything into account, on the whole, all things considered, in conclusion, as I have said, as was previously stated, to sum up, on balance	All in all, I strongly believe that computers are a useful tool.
To express cause and reason	as/since, because of, owing to, due to, for this reason	Lots of animals are endangered as/ since their natural habitats are being destroyed.
To express effect	therefore, thus, as a result, consequently, so, as a consequence	As a result many people have lost their jobs.
To emphasize what you say	clearly, obviously, of course, needless to say, in particular	Needless to say that eating healthy foods and exercising regularly reduce the risk of heart disease.
To express reality	in fact, actually, as a matter of fact, in practice, the fact of the matter is that	In fact, the report states that most college graduates are interested in Master’s degree.
To express difference between appearance and reality	on the face of it, at first sight, apparently	At first sight the building looked safe but after a detailed inspection it was reported to be in need of much repairs.
To state an argument against your opinion	it is popularly believed that, people often claim that, contrary to popular believe, it is a fact that, it is often alleged that, people argue that	Contrary to popular believe, the teaching profession is in need of qualified educators.
To state other people’s opinion	many people are in favour/against, some people argue that, a lot of people think/believe	Many people are against the proposal to raise local taxes.
To introduce the other side of the argument	opponents if this view say, however there are people/those who oppose … claim that	Opponents of this view say that increasing the school year will only overwork students.
To express balance	while, on the one hand, on the other hand, whereas	While working for a large company is prestigious, it can be very stressful.
To give examples	for example, for instance	For instance, statistics say this is a true fact.
To refer to what actually happens	in practice, in effect	In practice, consumers spend more money on luxury items.
To make general statements	as a rule, generally, I general, as a general rule, on the whole	As a rule, girls get better exam results than boys.
To express limit of knowledge	to the best of my knowledge, for all I know, as far as I know	As far as I know, residents have lived in this region for a long time.
To rephrase	that is to say, in other words	In other words, they disagreed.
To bring up other points or aspects	as far as….. is concerned, regarding, with regard to, as for	As far as the community is concerned, the area is in need of a new elementary school.
To imply that nothing else needs to be said	anyway, at any rate, in any case	At any rate, a new community center will greatly benefit the people of the town.
Accepting the situation	as it is, under the circumstances, things being as they are	Under the circumstances, the situation cannot be improved.
Showing result	as a result, therefore, consequently/ as a consequence, so, so/such…that	The ozone layer hole is getting bigger. As a result, the earth’s climate is changing.

TEACHER’S NOTES

TASK 1

1. informative

2. descriptive

3. critical

4. descriptive

TASK 4

Sentence 1              introduction (background)

Sentence 2             introduction (background)

Sentence 3             outline of major thesis

Sentence 4             method

Sentence 5             method

Sentence 6             results

Sentence 7             conclusion

 

TASK 6

Possible answers

1. definition

2. interrelation

3. scientists’ opinion about AI

4. capabilities of digital computer in the past

5. new technology development

6. early AI objectives

7. several approaches

You may use appendices as additional materials:

• Appendix 1 – articles for annotation writing
• Appendix 2 – linking devices