My watch list
my.chemeurope.com  
Login  

Quantum computer calculates exact energy of molecular hydrogen

Groundbreaking approach could impact fields from cryptography to materials science

13-Jan-2010

In an important first for a promising new technology, scientists have used a quantum computer to calculate the precise energy of molecular hydrogen. This groundbreaking approach to molecular simulations could have profound implications not just for quantum chemistry, but also for a range of fields from cryptography to materials science.

"One of the most important problems for many theoretical chemists is how to execute exact simulations of chemical systems," says author Alán Aspuru-Guzik, assistant professor of chemistry and chemical biology at Harvard University. "This is the first time that a quantum computer has been built to provide these precise calculations."

The work, described in Nature Chemistry, comes from a partnership between Aspuru-Guzik's team of theoretical chemists at Harvard and a group of experimental physicists led by Andrew White at the University of Queensland in Brisbane, Australia. Aspuru-Guzik's team coordinated experimental design and performed key calculations, while his partners in Australia assembled the physical "computer" and ran the experiments.

"We were the software guys," says Aspuru-Guzik, "and they were the hardware guys."

While modern supercomputers can perform approximate simulations of simple molecular systems, increasing the size of the system results in an exponential increase in computation time. Quantum computing has been heralded for its potential to solve certain types of problems that are impossible for conventional computers to crack.

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.

"Because classical computers don't scale efficiently, if you simulate anything larger than four or five atoms -- for example, a chemical reaction, or even a moderately complex molecule -- it becomes an intractable problem very quickly," says author James Whitfield, research assistant in chemistry and chemical biology at Harvard. "Approximate computations of such systems are usually the best chemists can do."

Aspuru-Guzik and his colleagues confronted this problem with a conceptually elegant idea.

"If it is computationally too complex to simulate a quantum system using a classical computer," he says, "why not simulate quantum systems with another quantum system?"

Such an approach could, in theory, result in highly precise calculations while using a fraction the resources of conventional computing.

While a number of other physical systems could serve as a computer framework, Aspuru-Guzik's colleagues in Australia used the information encoded in two entangled photons to conduct their hydrogen molecule simulations. Each calculated energy level was the result of 20 such quantum measurements, resulting in a highly precise measurement of each geometric state of molecular hydrogen.

"This approach to computation represents an entirely new way of providing exact solutions to a range of problems for which the conventional wisdom is that approximation is the only possibility," says Aspuru-Guzik.

Ultimately, the same quantum computer that could transform Internet cryptography could also calculate the lowest energy conformations of molecules as complex as cholesterol.

Facts, background information, dossiers
More about Harvard University
  • News

    New, long-lasting flow battery could run for more than a decade with minimum upkeep

    Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new flow battery that stores energy in organic molecules dissolved in neutral pH water. This new chemistry allows for a non-toxic, non-corrosive battery with an exceptionally long ... more

    Flat lens opens a broad world of color

    Last summer, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) announced a new, flat lens that could focus light with high efficiency within the visible spectrum. The lens used an ultrathin array of nanopillars to bend and focus light as it passed. ... more

    Mimicking nature's cellular architectures via 3-D printing

    Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being compressed. The plant's hardiness comes from a combination of its hollow, tubular macrostructure and porous microstructure. These archi ... more

  • Videos

    A diamond radio receiver

    Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences have made the world’s smallest radio receiver – built out of an assembly of atomic-scale defects in pink diamonds. This tiny radio — whose building blocks are the size of two atoms — can withstand extrem ... more

    A 3-D Material that Folds, Bends and Shrinks on its Own

    Harvard researchers have designed a new type of foldable material that is versatile, tunable and self actuated. It can change size, volume and shape; it can fold flat to withstand the weight of an elephant without breaking, and pop right back up to prepare for the next task. more

    New Polymers for Solar Power

    As part of the 2015–2016 Fellows’ Presentation Series at the Radcliffe Institute for Advanced Study, Scott T. Milner RI ’16 discusses current trends in solar power, how solar cells work, and how polymer-based materials may offer an attractive alternative to silicon. more

More about University of Queensland
  • News

    Tunable plastic thermometers

    Researchers at the Universities of Queensland and New South Wales in Australia have discovered that the ability of a plastic to conduct electricity can be tuned by exposure to an ion beam. Usually plastics conduct electricity so poorly that they are used as the insulation around electrical ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE