Abstract
Nuclear spins in certain solids couple weakly to their environment, making them attractive candidates for quantum information processing and inertial sensing. When coupled to the spin of an optically-active electron, nuclear spins can be rapidly polarized, controlled and read via lasers and radiofrequency fields. Possessing coherence times of several milliseconds at room temperature, nuclear spins hosted by a nitrogen-vacancy center in diamond are thus intriguing systems to observe how classical physical rotation at quantum timescales affects a quantum system. Unlocking this potential is hampered by precise and inflexible constraints on magnetic field strength and alignment in order to optically induce nuclear polarization, which restricts the scope for further study and applications. In this work, we demonstrate optical nuclear spin polarization and rapid quantum control of nuclear spins in a diamond physically rotating at $1\,$kHz, faster than the nuclear spin coherence time. Free from the need to maintain strict field alignment, we are able to measure and control nuclear spins in hitherto inaccessible regimes, such as in the presence of a large, time-varying magnetic field that makes an angle of more than $100^\circ$ to the nitrogen-lattice vacancy axis. The field induces spin mixing between the electron and nuclear states of the qubits, decoupling them from oscillating rf fields. We are able to demonstrate that coherent spin state control is possible at any point of the rotation, and even for up to six rotation periods. We combine continuous dynamical decoupling with quantum feedforward control to eliminate decoherence induced by imperfect mechanical rotation. Our work liberates a previously inaccessible degree of freedom of the NV nuclear spin, unlocking new approaches to quantum control and rotation sensing.
Highlights
Robust solid-state substrates such as diamond confer an important advantage to the spin qubits hosted within: Coherent operation in real-world environments at room temperature
We have demonstrated quantum measurement and control of an ensemble of nuclear spins rotating in the presence of a large, off-axis magnetic field
For the first time, how feed forward of the rf drive can be used to maintain coherent control of the nuclear spins even when the magnetic field is orthogonal to the NV axis
Summary
Robust solid-state substrates such as diamond confer an important advantage to the spin qubits hosted within: Coherent operation in real-world environments at room temperature. The NVnuclear-spin system typically must be deployed with the strict condition of magnetic field alignment parallel to the NV axis This inflexible requirement severely restricts the usefulness of nuclear spins in scenarios where the motional and rotational degrees of freedom of a quantum system are not fixed [4,34,35,36]. We use feed-forward control to eliminate the significant frequency shifts imposed by the off-axis magnetic field and dynamical decoupling to suppress the deleterious aspects of mechanical rotation This quantum decoupling sequence can be made to eliminate any detectable effects of physical rotation on-demand: Preserving the nuclear spins through an entire cycle of rotation in the presence of a noisy perturbation and demonstrating the precise level of control our experiments can achieve
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