Coherent singlet-triplet oscillations in a silicon-based double quantum dot

Exploiting the weak interactions between electron spins and nuclear spins in silicon-based quantum dots leads to a dephasing time two orders of magnitude greater than in analogous gallium-arsenide-based devices, demonstrating the potential of silicon as a host material for quantum information processing. Silicon chips make quantum leap Silicon is the established platform for microelectronics, and may yet fulfill a similar role for quantum technologies. Standard fabrication techniques already allow the isolation of single electron spins in silicon transistor-like devices, and these single spins can be used as quantum bits, or qubits. Unfortunately, such qubits tend to lose their information quickly as a result of interaction between electron and nuclear spins. Here Maune et al . demonstrate a coherently controlled silicon-based qubit that contains far fewer nuclear spins and achieves much longer quantum memory times. Used in combination with fast qubit initialization and read-out, such devices could pave the way towards practical silicon-based quantum information processing . Silicon is more than the dominant material in the conventional microelectronics industry: it also has potential as a host material for emerging quantum information technologies. Standard fabrication techniques already allow the isolation of single electron spins in silicon transistor-like devices. Although this is also possible in other materials, silicon-based systems have the advantage of interacting more weakly with nuclear spins. Reducing such interactions is important for the control of spin quantum bits because nuclear fluctuations limit quantum phase coherence, as seen in recent experiments in GaAs-based quantum dots 1 , 2 . Advances in reducing nuclear decoherence effects by means of complex control 3 , 4 , 5 still result in coherence times much shorter than those seen in experiments on large ensembles of impurity-bound electrons in bulk silicon crystals 6 , 7 . Here we report coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure and show that this system has a nuclei-induced dephasing time of 360 nanoseconds, which is an increase by nearly two orders of magnitude over similar measurements in GaAs-based quantum dots. The degree of phase coherence observed, combined with fast, gated electrical initialization, read-out and control, should motivate future development of silicon-based quantum information processors.