## Wednesday, January 13, 2010 ... //

### Quantum computer calculates hydrogen molecule

In the middle of crazy articles about the need for the world to team up and fight against the laws of physics such as climate change, The Harvard Crimson has also pointed out a very interesting piece of science.

Nature Chemistry has published a really fun article:

B. P. Lanyon & 11 co-authors: Towards quantum chemistry on a quantum computer
The American and Australian authors use the latest "photonic" quantum computer technology to calculate the complete spectrum of the hydrogen molecule to 20 bits of precision (almost one part per million accuracy). This is not just some emulation of one "continuous" quantum object by its equally "analog" model. This is a real, "q-digital" calculation.

Of course, the hydrogen molecule is not meant to be the final word in this line of research. When they look at more complex molecules, the quantum computers should really show their exponentially stronger muscles - relatively to ordinary supercomputers. While NIST just celebrated their most accurate "classical" calculation of the properties of lithium, using a supercluster, the quantum technologies could take over this industry in a near future.

The "photonic" quantum computers seem to be pretty ordinary arrangements of lasers. In 2008, the team similar to the present one - and independently Chao-Yang Lu and his or her equally Chinese collaborators - showed that this technology is enough to implement a famous factorization Al Gore Rhythm of an occasional TRF reader and commenter, Peter Shor.

See my introduction to quantum computing and Shor's algorithm.

These "photonic" quantum computers are technically two-qubit computers, well below the 64 bits of your newest Windows 7 laptop, but with a proper separation of the calculation to many steps, they can do a very useful job, anyway.