We introduce and demonstrate a scheme for eliminating the inhomogeneous dephasing of a collective quantum state. The scheme employs off-resonant fields that continuously dress the collective state with an auxiliary sensor state, which has an enhanced and opposite sensitivity to the same source of inhomogeneity. We derive the optimal conditions under which the dressed state is fully protected from dephasing when using either one or two dressing fields. The latter provides better protection, circumvents qubit phase rotation, and suppresses the sensitivity to drive noise. We further derive expressions for all residual, higher-order sensitivities. We experimentally study the scheme by protecting a collective excitation of an atomic ensemble, where inhomogeneous dephasing originates from thermal motion. Using photon storage and retrieval, we demonstrate complete suppression of inhomogeneous dephasing and, consequently, a prolonged memory time. Our scheme may be applied to eliminate motional dephasing in other systems, improving the performance of quantum gates and memories with neutral atoms. It is also generally applicable to various gas, solid, and engineered systems, where sensitivity to variations in time, space, or other domains limits possible scale-up of the system.

中文翻译：

---

持续保护集体国家免于非同相移相

我们介绍并演示了一种用于消除集体量子态不均匀相移的方案。该方案采用了非共振场，该场利用辅助传感器状态连续地修饰了集体状态，该状态对相同的非均匀性源具有增强的和相反的灵敏度。我们推导出了最佳条件，在该条件下，当使用一个或两个修整场时，可以充分保护修整状态以防止移相。后者提供了更好的保护，避免了量子比特相位旋转，并抑制了对驱动噪声的敏感性。我们进一步导出所有剩余的高阶灵敏度的表达式。我们通过保护原子团的集体激发来实验研究该方案，其中不均相移相是由热运动引起的。使用光子存储和检索，我们证明了完全抑制了不均匀的相移，因此延长了存储时间。我们的方案可用于消除其他系统中的运动相移，从而改善具有中性原子的量子门和存储器的性能。它通常还适用于各种气体，固体和工程系统，其中对时间，空间或其他域变化的敏感性限制了系统的可能扩大规模。