Quantum control of nuclear spin qubits in a rapidly rotating diamond

TL;DR

This paper demonstrates rapid optical control and polarization of nuclear spins in a diamond NV center during high-speed rotation, overcoming previous constraints on magnetic field alignment and enabling new quantum control and sensing techniques.

Contribution

It introduces a method for controlling nuclear spins in a rotating diamond without strict magnetic field alignment, allowing quantum control during fast rotation and large magnetic field variations.

Findings

Nuclear spins can be optically polarized in a rotating diamond at 1 kHz.

Coherent spin control is achievable at any rotation point, even with large magnetic field angles.

Decoherence from rotation is mitigated using dynamical decoupling and quantum feedforward.

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.