NMR implementation of a building block for scalable quantum computation

We report the implementation of the central building block of the Schulman–Vazirani procedure for fully polarizing a subset of two-level quantum systems which are initially only partially polarized. This procedure consists of a sequence of unitary operations and incurs only a quasi-linear overhead in the number of quantum systems and operations required. The key building block involves three quantum systems and was implemented on a homonuclear three-spin system using room temperature liquid-state nuclear magnetic resonance (NMR) techniques. This work was inspired by the state initialization challenges in current NMR quantum computers but also shines new light on polarization transfer in NMR.