Dr. Go Yusa (Tohoku Univ.)

Title: Controlled multiple quantum coherences of nuclear spins in a 
nanometer-scale device

Abstract:  Nuclear magnetic resonance (NMR), which is based on coherent 
quantum mechanical superposition of nuclear spin states, has found far 
reaching application as an analytical tool. Recently, it has received 
considerable renewed interest since such coherence and its control 
constitute the operation of a qubit, the smallest element of quantum 
computation and information processing. However, standard NMR is not 
suitable for realistic and scalable device implementation, for which 
all-electrical control and detection of microscopic quantities of 
coherent nuclear spins are required. Here we present a self-contained 
gallium arsenide (GaAs) semiconductor device with a novel paradigm of 
NMR, which accesses nuclear spins in a nanometer-scale region. The new 
method, which is based on detecting longitudinal magnetization Mz of 
nuclear spins by the resistance of the device, allows direct detection 
of otherwise invisible multiple quantum coherences between levels 
separated by more than one quantum of spin angular momentum. This 
capability provides not only a versatile multiple qubit device, but also 
a new microscopic high sensitivity NMR technique especially suitable for 
probing materials containing nuclei forming multiple spin levels.