Southwest Quantum Information and Technology

Arbitrary Dicke-state control of symmetric Rydberg ensembles

Presenting Author: Tyler Keating, Biedermann-Deutsch group (New Mexico/Sandia)
Contributing Author(s): Charles H. Baldwin, Yuan-Yu Jau, Grant W. Biedermann, Ivan H. Deutsch

The Rydberg blockade is a versatile tool for quantum information in neutral atoms. While the blockade is, at its heart, a two-body effect, it can be naturally used to generate many-body entanglement by creating single, collective excitations across ensembles of atoms. Given a strong blockade, such an ensemble is isomorphic to the Jaynes-Cummings model (JCM): the presence/absence of a Rydberg excitation plays the role of a qubit, while the atoms' hyperfine ground states take the place of photons. By applying symmetric raman transitions to a blockaded ensemble, we can generate SU(2) rotations on the "photon number" degree of freedom; this gives a control Hamiltonian with no clear analogue in a cavity-based JCM. We show that such raman transitions, along with Rydberg excitation, make the system controllable within its symmetric subspace. Arbitrary, symmetric n-body states can therefore be produced, including highly entangled Dicke and cat states. Depending on the laser powers and detunings used, one can control either the complete (2n+1)-dimensional symmetric space or just the (n+1)-dimensional dressed-ground manifold. We discuss the advantages and disadvantages of each, and show simulated entanglement generation among 7 atoms in both regimes. For a wide range of parameters, the time required to generate maximal entanglement is independent of atom number, so this technique could be especially useful for rapidly entangling large ensembles.

(Session 9a : Friday from 4:30 pm - 5:00 pm)