Quantum Coherence\nControl at Temperatures up to 1400\nK

Coherent quantum control at high temperatures is important\nfor\nexpanding the quantum world and is useful for applying quantum technologies\nto realistic environments. Quantum control of spins in diamond has\nbeen demonstrated near 1000 K, with the spins polarized and read out\nat room temperature and controlled at elevated temperatures by rapid\nheating and cooling. Further increase of the working temperature is\nchallenging due to fast spin relaxation in comparison with the heating\nand cooling rates. Here we significantly improve the heating and cooling\nrates by using reduced graphene oxide as the laser absorber and heat\ndrain and hence realize coherent quantum operation at up to 1400 K,\nwhich is higher than the Curie temperatures of all known materials.\nThis work facilitates the use of diamond sensors to study a wide range\nof magnetic effects in the high-temperature regime, such as thermoremanent\nmagnetism and magnetic shape memory effects.