Congratulations to the SDK team for finally publishing the long paper! 

This is a cumulative effort driven persiverantly by Liyang. Important support are from other team members, in particular Yizun whose contribution to the parallel OAWG setup is invaluable. 

As discussed in this paper, sometime speed is key to achieve high quality quantum control that could appear mysterious classically. So, let's move fast toward new progresses -- by Lingjing, Jiangyong, and our new members :)

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Atoms are ideal quantum sensors. To register spatial-dependent interactions, atoms are split into a superposition of displaced paths to accumulate the phase difference. This atom interferometric insight is widely exploited in state-of-art technologies from atom-based quantum measurements and simulations to ion-based quantum computation. A corner stone in these developments is to split matterwave by exerting path-dependent stimulated optical forces, a technique known for its typically moderate fidelity. We show that by directly encoding hyperfine alkaline “spins” to the interferometric paths, spin-dependent recoil kicks (SDK) can be robustly driven by Raman pulses with exquisite precision. 

Our technique is a high-speed extension of traditional Raman matterwave control, operated in a previously unfavored regime prone to unwanted multi-level dynamics. We find the seemingly complex internal-state dynamics can be managed with composite pulses, for precise control of the multiple spins defined on the hyperfine manifold. The speed is key to freeze the continuous atomic motion and to protect cancellation of low-frequency noises. Experimentally, the counter-propagating short pulses are spatially resolved on an optical delay line to facilitate directional “kicks” with wideband optical pulse programming. We impart hundreds of photon recoils within a few microseconds to a mesoscopic sample. Our numerical model suggests that the SDK technique can robustly support multi-recoil transfer to multi-spinor matterwave with ~99%-level phase gate fidelity.

The fast and precise SDK is important for quantum-enhanced precision measurements with spin-squeezed samples. With improved laser power, our SDK technique may also drastically enhance the large-momentum-splitting benefits for inertial sensing with atom interferometers.