Monday, July 26, 2010

Free text: An Introductory Course on Quantum Mechanics

This was just posted on arXiv the other day: An Introductory Course on Quantum Mechanics by Bram Gaasbeek. The abstract:

This is a very gentle introductory course on quantum mechanics aimed at the first years of the undergraduate level. The basic concepts are introduced, with many applications and illustrations. Contains 12 short chapters of equal length, ideal for a one term course. The license allows reuse of figures and text under the Attribution-Noncommercial-ShareAlike conditions.

I skimmed through the table of contents and some of the text: some of the early chapters definitely seems applicable to some one new to quantum computing. I know I ended up spending quite a bit of money on books when I first started researching the subject, so one posted on arXiv is certainly a plus.

Monday, July 19, 2010

arXiv: Hiding Quantum Information in the Perfect Code

Here's another recent one from arXiv: Hiding Quantum Information in the Perfect Code by Shaw and Brun out of the University of Southern California. The abstract:

We present and analyze a protocol for quantum steganography where the sender (Alice) encodes her steganographic information into the error syndromes of the perfect (five-qubit) quantum error-correcting code, and sends it to the receiver (Bob) over a depolarizing channel. Alice and Bob share a classical secret key, and hide quantum information in such a way that to an eavesdropper (Eve) without access to the secret key, the quantum message looks like an innocent codeword with a typical sequence of quantum errors. We calculate the average rate of key consumption, and show how the protocol improves in performance as information is spread over multiple codeword blocks. Alice and Bob utilize different encodings to optimize the average number of steganographic bits that they can send to each other while matching the error statistics of the depolarizing channel.

As the paper says, there hasn't been much work in quantum steganography. It isn't my research area, but I think this is one of the few pieces on the subject that I've come across.

arXiv: Simulating Chemistry with Quantum Computers

I came across this in today's arXiv listing: Simulating Chemistry with Quantum Computers. Here's the abstract:

The difficulty of simulating quantum systems, well-known to quantum chemists, prompted the idea of quantum computation. One can avoid the steep scaling associated with the exact simulation of increasingly large quantum systems on conventional computers, by mapping the quantum system to another, more controllable one. In this review, we discuss to what extent the ideas in quantum computation, now a well-established field, have been applied to chemical problems. We describe algorithms that achieve significant advantages for the electronic-structure problem, the simulation of chemical dynamics, protein folding, and other tasks. Although theory is still ahead of experiment, we outline recent advances that have led to the first chemical calculations on small quantum information processors.

It is well known that a simulation of a general quantum system on a classical computer experiences an exponential slow down. As the title states, this paper describes how a quantum computer can be used to avoid this problem in Chemistry.