Fig. 1. Schematic diagram of the MQA. The cold atomic ensemble A1 is free-falling in the vacuum chamber. Atomic vapor A2, the vacuum chamber, and all optical elements are fixed on and move with the platform at acceleration a. The distance between A1 and A2 is changed from L0 to L0+ΔL. ΔL is the acceleration-dependent displacement achieved via atom–light quantum interference, which is realized in three steps. Step 1: a^1 and S^a1(1) are generated by the first stimulated Raman scattering (SRS) in A1 via input seed a^0 and Raman pump P1. The atomic spin wave is S^aj(i), where superscript i (i=1, 2) indicates different atomic ensemble A1 or A2, and subscript j (j=1, 2, 3) represents the evolution state at different times of atomic ensemble Ai. Step 2: a^1 is stored in A2 as S^a1(2) is driven by the strong write pulse W. After memory time tM, S^a2(2), evolved from S^a1(2) due to atomic decay, is retrieved back to a^2 by the read pulse R. Step 3: S^a2(1), evolved from S^a1(1) during the memory time, and a^2 interfere by the second SRS via Raman pump P2.

Fig. 2. (a) Quantum enhancement factor Qe versus T1 and T2′ when G2=2 and 8, respectively. (b) Sensitivity versus s and G2 when T1=0.5 and 1, respectively. s=T2′/T1 is the ratio of two beams’ losses. The red curves mark Qe=1 for SNL. Sensitivities within the red curves can beat the SNL. Parameter settings: N0=106, G1=8, λs=795  nm, and tM=1  ms.

Fig. 3. Sensitivity as a function of bandwidth under the conditions G=8, N0=106, λs=795  nm, and η=1. The data of other reported accelerometers are given as comparison. Dark green diamond: microchip optomechanical accelerometer [14]. Orange pentagram: micromechanical capacitive accelerometer [18]. Purple hexagram: MEMS accelerometer [6]. Gray circle: optical accelerometer [15].