Atomic spin-wave control and spin-dependent kicks with shaped subnanosecond pulses

Abstract

The absorption of traveling photons resonant with electric dipole transitions of an atomic gas naturally leads to electric dipole spin wave excitations. For a number of applications, it would be highly desirable to shape and coherently control the spatial waveform of the spin waves before spontaneous emission can occur. This work details a recently developed optical control technique to achieve this goal, where counter-propagating, shaped sub-nanosecond pulses impart sub-wavelength geometric phases to the spin waves by cyclically driving an auxiliary transition. In particular, we apply this technique to reversibly shift the wave vector of a spin wave on the D2 line of laser-cooled 87 Rb atoms, by driving an auxiliary D1 transition with shape-optimized pulses, so as to shut off and recall superradiance on demand. We investigate a spin-dependent momentum transfer during the spin-wave control process, which leads to a transient optical force as large as ∼ 1 k/ns, and study the limitations to the achieved 70 ∼ 75% spin wave control efficiency by jointly characterizing the spin-wave control and matterwave acceleration. Aided by numerical modeling, we project potential future improvements of the control fidelity to 99% level when the atomic states are better prepared and by equipping a faster and more powerful pulse shaper. Our technique also enables a backgroundfree measurement of the superradiant emission to unveil the precise scaling of the emission intensity and decay rate with optical depth for the first time to our knowledge.

Exploiting the Photonic Non-linearity of Free Space Subwavelength Arrays of Atoms

“…First, we have discussed how to coherently excite dark modes of subwavelength arrays using a Raman lasers. This techniques represents a novel alternative to already proposed optical phase imprinting techniques [40][41][42]. Second, we described how to realise a universal set of gates based on dipole-blockade between qubit states.…”

Renormalization group analysis of near-field induced dephasing of optical spin waves in an atomic medium

“…This narrow emission occurs due to constructive interference of the emitting atoms along the k direction, and forms the basis of collective enhancement at the heart of efficient atom-light interfaces [12,59] and the applications mentioned in the introduction. This behavior can be equally derived by microscopic theories [58] or by the macroscopic MBE [16,54,55].…”

Amplification of arbitrary frequency chirps of pulsed light on nanosecond timescales

“…Competition with spontaneous emission from excited states, which typically occurs on the 10s of ns timescale, requires pulses and chirps of short duration. Specific applications employing chirped-pulse population transfer include: driving Raman transitions [14][15][16]; manipulation of atomic spin-waves [17,18]; laser cooling of atoms via sawtooth wave adiabatic passage [19,20]; strong optical forces on atoms [21,22] and molecules [23]; light-induced ultracold collisions [24][25][26][27]; ultracold molecule formation by photoassociation [28,29]; and high-speed spectroscopic gas sensing [30].…”