Experimental application of decoherence-free subspaces in an optical quantum-computing algorithm

Phys Rev Lett. 2003 Oct 31;91(18):187903. doi: 10.1103/PhysRevLett.91.187903. Epub 2003 Oct 31.


For a practical quantum computer to operate, it is essential to properly manage decoherence. One important technique for doing this is the use of "decoherence-free subspaces" (DFSs), which have recently been demonstrated. Here we present the first use of DFSs to improve the performance of a quantum algorithm. An optical implementation of the Deutsch-Jozsa algorithm can be made insensitive to a particular class of phase noise by encoding information in the appropriate subspaces; we observe a reduction of the error rate from 35% to 7%, essentially its value in the absence of noise.