Experimental protection of quantum coherence by using a phase-tunable image drive

The protection of spin coherence is an essential task in order to manipulate, store and read quantum information. It has been proposed to dynamically decouple (DD) qubits from their surroundings by applying a series of distinct pulses¹. For nitrogen vacancy centers, such protection was achieved by using concatenated DD up to the second order of dressing². We go beyond their specific case and demonstrate T2~T1 with a new pulse protocol, independent of qubit initial state, in a number of materials with different spin Hamiltonians and environments³. The protocol uses two coherent microwave pulses: one drives the Rabi precession while a low-power, circularly polarized (image) pulse continuously sustains the spin motion. The initial phase of the image drive allows tuning the spin dynamics by altering the Floquet modes. The technical implementation is simple and can be generalized to any type of qubit, such as superconducting circuits or spin systems.
1. L. Viola, S. Lloyd, PRA 58, 2733 (1998).
2. D. Farfurnik, et al, PRA 96, 013850 (2017).
3. S. Bertaina et al, arXiv:2001.02417, to appear.