Daniel Oblak

Mesoscopic atomic entanglement for precision measurements beyond the standard quantum limit

Squeezing of quantum fluctuations by means of entanglement is a well-recognized goal in the field of quantum information science and precision measurements. In particular, squeezing the fluctuations via entanglement between 2-level atoms can improve the precision of sensing, clocks, metrology, and spectroscopy. Here, we demonstrate 3.4 dB of metrologically relevant squeezing and entanglement for ≳ 105 cold caesium atoms via a quantum nondemolition (QND) measurement on the atom clock levels. We show that there is an optimal degree of decoherence induced by the quantum measurement which maximizes the generated entanglement. A 2-color QND scheme used in this paper is shown to have a number of advantages for entanglement generation as compared with a single-color QND measurement.

Entanglement-assisted atomic clock beyond the projection noise limit

We use a quantum non-demolition measurement to generate a spin squeezed state and to create entanglement in a cloud of 105 cold cesium atoms. For the first time we operate an atomic clock improved by spin squeezing beyond the projection noise limit in a proof-of-principle experiment. For a clock-interrogation time of 10u2009μs, the experiments show an improvement of 1.1u2009dB in the signal-to-noise ratio, compared to the atomic projection noise limit.

Nondestructive Probing of Rabi Oscillations on the Cesium Clock Transition near the Standard Quantum Limit

We report on the nondestructive observation of Rabi oscillations on the Cs clock transition. The internal atomic state evolution of a dipole-trapped ensemble of cold atoms is inferred from the phase shift of a probe laser beam as measured using a Mach-Zehnder interferometer. We describe a single color as well as a two-color probing scheme. Using the latter, measurements of the collective pseudospin projection of atoms in a superposition of the clock states are performed and the observed spin fluctuations are shown to be close to the standard quantum limit.

Spin squeezing of atomic ensembles by multicolor quantum nondemolition measurements

We analyze the creation of spin squeezed atomic ensembles by simultaneous dispersive interactions with several optical frequencies. A judicious choice of optical parameters enables optimization of an interferometric detection scheme that suppresses inhomogeneous light shifts and keeps the interferometer operating in a balanced mode that minimizes technical noise. We show that when the atoms interact with two-frequency light tuned to cycling transitions the degree of spin squeezing

Inhomogeneous light shift effects on atomic quantum state evolution in non-destructive measurements

{ensuremath{xi}}^{2}

Nondestructive interferometric characterization of an optical dipole trap

scales as

Diffraction effects on light-atomic-ensemble quantum interface

{ensuremath{xi}}^{2}ensuremath{sim}1/d

Squeezing of atomic quantum projection noise

, where

Echo spectroscopy of atomic dynamics in a Gaussian trap via phase imprints

d

Mesoscopic Non-classical Atomic States for Quantum Information and Metrology

is the resonant optical depth of the ensemble. In real alkali metal atoms there are loss channels and the scaling may be closer to