Quantum register of fermion pairs

Quantum control of motional states is crucial for quantum science, ranging from quantum metrology to information processing. However, the motional coherence of individual particles can be fragile to maintain, as external degrees of freedom couple strongly to the environment. Systems in nature can host robust motional coherence by harnessing the power of the symmetry of fermion pairs, such as electrons in helium and Cooper pairs. In this work, we demonstrate a novel architecture to encode information in the motional state of a pair of fermions. Coherent control is realized via modulation of interactions between the atoms and the nonlinearity of the trapping potential. The energy difference between the two motional states is set by the atomic recoil energy, is dependent on only the mass and the lattice wavelength, and is insensitive to the noise of the confining potential. In this experiment, we observe quantum coherence beyond ten seconds. The methods presented here will enable coherently programmable quantum simulators of many-fermion systems, precision metrology based on atom pairs and molecules and, by implementing further advances, digital quantum computation using fermion pairs.