A large-momentum-transfer Raman atom interferometer without $k$-reversal

We present a Raman atom interferometer using large momentum transfer without reversing the direction of the effective wavevector ($k$-reversal). More specifically, we use a microwave $\pi$/2 pulse to manipulate the spin state of $^{87}$Rb atoms before applying a Raman light $\pi$ pulse to achieve 4$\hbar k$ momentum transfer per Raman light pulse. A microwave $\pi$ pulse in the middle of the interferometer sequence reverses the spin states, which allows closing of the interferometer arms by the same Raman light $\pi$ pulses without propagation reversal. We present a proof-of-principle demonstration of a 4$\hbar k$ large-momentum-transfer (LMT) atom interferometer and discuss its scalability. Our results extend the scope of using LMT atom optics.