Entanglement-Enhanced Interferometry with Neutral Atoms.

Anonymous

Constantin Brif, Brandon Ruzic, Grant W. Biedermann

Recent progress in generating entangled spin states of neutral atoms provides opportunities to advance quantum sensing technology.In particular, entanglement can enhance the performance of accelerometers and gravimeters based on light-pulse atom interferometry.We study the effects of error sources that may limit the sensitivity of such devices, including errors in the preparation of the initial entangled state, imperfections in the laser pulses, momentum spread of the initial atomic wave packet, measurement errors, spontaneous emission, and atom loss.We determine that, for each of these errors, the expectation value of the parity operator has the general form = 0 cos(N φ), where φ is the interferometer phase and N is the number of atoms prepared in the maximally entangled Greenberger-Horne-Zeilinger state.Correspondingly, the minimum phase uncertainty has the general form φ = ( 0 N ) -1 .Each error manifests itself through a reduction of the amplitude of the parity oscillations, 0 , below the ideal value of 0 = 1.For each of the errors, we derive an analytic result that expresses the dependence of 0 on error parameter(s) and N , and also obtain a simplified approximate expression valid when the error is small.Based on the performed analysis, entanglement-enhanced atom interferometry appears to be feasible with existing experimental capabilities.

Yanhua H. Shih

Sascha H. Hauck, Vladimir M. Stojanović

Theoretical studies of coherent atom transport have as yet mainly been restricted to one-dimensional model systems with harmonic trapping potentials. Here we investigate this important phenomenon---a prerequisite for a variety of quantum-technology applications based on cold neutral atoms---under much more complex physical circumstances. More specifically yet, we study fast atomic transport in a moving double-well optical lattice, whose three-dimensional (anharmonic) potential is nonseparable in the $x$-$y$ plane. We first propose specific configurations of acousto-optic modulators that give rise to the moving-lattice effect in an arbitrary direction in this plane. We then determine moving-lattice trajectories that enable single-atom transport using two classes of quantum-control methods: shortcuts to adiabaticity (STA), here utilized in the form of inverse engineering based on a quadratic-in-momentum dynamical invariant of Lewis-Riesenfeld type, and their recently proposed modification termed enhanced STA (eSTA). Subsequently, we quantify the resulting single-atom dynamics by numerically solving the relevant time-dependent Schr\"odinger equations and compare the efficiency of STA- and eSTA-based transport by evaluating the respective fidelities. We show that---except for the regime of shallow lattices---the eSTA method consistently outperforms its STA counterpart. This study has direct implications for neutral-atom quantum computing based on collisional entangling two-qubit gates and quantum sensing of constant homogeneous forces via guided-atom interferometry.

U Dorner

We discuss strategies for quantum enhanced estimation of atomic transition frequencies with ions stored in Paul traps or neutral atoms trapped in optical lattices. We show that only marginal quantum improvements can be achieved using standard Ramsey interferometry in the presence of collective dephasing, which is the major source of noise in relevant experimental setups. We therefore analyze methods based on decoherence free subspaces and prove that quantum enhancement can readily be achieved even in the case of significantly imperfect state preparation and faulty detections.

Kishore T. Kapale