High-Compton-frequency, parity-independent, mesoscopic Schrodinger-cat-state atom interferometer with Heisenberg-limited sensitivity

We present a protocol for an atomic interferometer that reaches the Heisenberg limit (HL), within a factor of similar to root 2, via collective state detection and critical tuning of one-axis twist spin squeezing. It generates a Schrodinger cat state, as a superposition of two extremal collective states. When this Schrodinger-cat-state interferometer is used as a gyroscope, the interference occurs at an ultrahigh Compton frequency, corresponding to a mesoscopic single object with a mass of Nm, where N is the number of particles in the ensemble, and m is the mass of each particle. For Rb-87 atoms, with N = 10(6), for example, the interference would occur at a Compton frequency of similar to 2 x 10(31) Hz. Under this scheme, the signal is found to depend critically on the parity of N. We present two variants of the protocol. Under protocol A, the fringes are narrowed by a factor of N for one parity, while for the other parity the signal is zero. Under protocol B, the fringes are narrowed by a factor of N for one parity, and by a factor of root N for the other parity. Both protocols can be modified in a manner that reverses the behavior of the signals for the two parities. Over repeated measurements under which the probability of being even or odd is equal, the averaged sensitivity is smaller than the HL by a factor of similar to root 2 for both versions of the protocol. We describe an experimental scheme for realizing such an atomic interferometer, and discuss potential limitations due to experimental constraints imposed by the current state of the art, for both collective state detection and one-axis-twist squeezing. We show that when the Schrodinger-cat-state interferometer is configured as an accelerometer, the effective two-photon wave vector is enhanced by a factor of N, leading to the same degree of enhancement in sensitivity. We also show that such a mesoscopic single object can be used to increase the effective base frequency of an atomic clock by a factor of N, with a sensitivity that is equivalent to the HL, within a factor of similar to root 2.