Ensembles of neutral atoms enable state-of-the-art measurements of time, acceleration, and electromagnetic fields. Introducing entanglement among the constituent atoms offers a route to enhancing the precision of these measurements. One proposed approach to generating the requisite entanglement relies on the off-resonant optical coupling of one ground state to a highly excited electronic state. This technique, known as Rydberg dressing, enables local and dynamical control of interactions between neutral atoms. In this talk, I will present the engineering of Rydberg-dressed interactions by single-photon coupling to nP states in a cesium atomic clock. I will also present the creation of a squeezed spin state by local interactions that achieves a factor of 0.78(4) reduction in phase variance below the standard quantum limit.
This Conference Presentation, One-axis twisting in a Rydberg-dressed atomic clock was recorded at Photonics West 2020 held in San Francisco, California, United States.
Nonlocal light-mediated interactions between cold atoms coupled to the mode of an optical cavity present unique prospects for simulating the quantum dynamics of strongly-interacting many-body systems. In a recent publication, we introduced a tunable, nonlocal sparse spin network that can be engineered in near-term single-mode cavity QED platforms.1 In this companion paper, we study this spin network in detail and pedagogically review its basic dynamical properties, providing theoretical details and calculations that expand on the statements made in our original publication. We show that the network exhibits two distinct notions of emergent geometry - linear and treelike - that can be accessed using a single tunable parameter. In either of these two extreme limits, we find a succinct description of the resulting dynamics in terms of two distinct metrics on the network, encoding a notion of either linear or treelike distance between spins. We also show that the network can be mapped in these two extreme limits onto exactly solvable models: a linear Heisenberg spin chain in one limit, and a Dyson hierarchical model in the other. These observations highlight the essential role played by the geometry of the interaction structure in determining a system's dynamics, and raise prospects for novel studies of nonlocal and highly chaotic quantum dynamics in near-term experiments.
We analyze the dynamics of spin-mixing interactions generated by coupling spin-1 atoms to the mode of a high-finesse optical cavity. We show that the dynamics can be understood in terms of generators of the noncompact Lie group SU(1, 1) and introduce a set of SU(1, 1) coherent states which are preserved under Hamiltonian evolution. In terms of these coherent states the resulting dynamics may be interpreted as classical motion on the unit disk. We explicitly compute the trajectories of this classical motion and show that the motion is equivalent to spin-nematic squeezing in the atomic ensemble. Non-uniform coupling between the atomic ensemble and the cavity mode leads to departures from this simple behavior; we introduce a toy model that captures this non-uniformity and solve it exactly.
Detection noise poses a challenge for achieving Heisenberg-limited phase estimation. We discuss a "twisting echo" protocol1 that addresses this problem by using interactions to amplify a spectroscopic signal. The echo protocol enables phase sensitivity near the Heisenberg limit while permitting detection noise on the order of the quantum noise of an unentangled state. For comparison with conventional schemes requiring direct detection of entangled states, we calculate the dependence of metrological gain on detection noise in Ramsey spectroscopy with squeezed, twin Fock, and GHZ states. The twisting echo outperforms all of these alternatives if the detection uncertainty is at or above the single-atom level.
Atomic clocks have reached the Standard Quantum Limit (SQL) of precision,1 set by the projection noise
inherent in measurements on uncorrelated atoms. It is possible to overcome this limit by entangling the atoms to
generate a "squeezed state" of the atomic ensemble. We use the collective interaction of an atomic ensemble with
a far-detuned light field in an optical resonator to prepare squeezed states by two different methods: quantum
non-demolition (QND) measurement and Hamiltonian evolution. We apply both methods to an ensemble of
5 x 10487Rb atoms in a superposition of hyperfine clock states. We measure the suppression of projection
noise and compare it to the accompanying reduction in signal, thereby quantifying the net gain in spectroscopic
sensitivity.
By QND measurement, with resolution up to 9 dB below the projection noise level, we achieve 3.0(8) dB of
metrologically relevant squeezing. Whereas the measurement-based approach relies on knowledge of the (randomly
distributed) measurement outcome to produce a conditionally squeezed state, the method of Hamiltonian
evolution produces a known squeezed state independent of detector performance. We mimic the dynamics of the
one-axis twisting Hamiltonian, proposed as a generator of squeezed states by Kitagawa and Ueda,2 by using the
atom-induced frequency shift of the resonator mode and the corresponding resonator-field-induced shift of the
atomic transition frequency to introduce an effective interaction among the atoms. The resulting deterministic
squeezing is sufficient to allow a 6.0(4) dB improvement in spectroscopic sensitivity over the SQL.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.