Coherent Coupling of Alkali Atoms by Random Collisions

Abstract

Random spin-exchange collisions in warm alkali vapor cause rapid decoherence and act to equilibrate the spin state of the atoms in the vapor. In contrast, here we demonstrate experimentally and theoretically a coherent coupling of one alkali species to another species, mediated by these random collisions. We show that the minor species (potassium) inherits the magnetic properties of the dominant species (rubidium), including its lifetime (T_{1}), coherence time (T_{2}), gyromagnetic ratio, and spin-exchange relaxation-free magnetic-field threshold. We further show that this coupling can be completely controlled by varying the strength of the magnetic field. Finally, we explain these phenomena analytically by mode mixing of the two species via spin-exchange collisions.

Study of Atomic Populations, Electromagnetically Induced Transparency, and Dispersive Signals in a λ-Type System Under Various Decoherence Effects

“…We have considered the fixed values of Ω /(2 ) = 5.0 MHz, Ω /(2 ) = 0.1 MHz, and Γ/(2 ) = 6.0 MHz. All the numerical values of the various decoherence rates are taken within the ranges of available data in papers [19][20][21][22][23][24][25][26][27][28][29][30][31].…”

“…Γ are the population decay rates between the levels |1⟩, |2⟩ and |3⟩ ( , = 1, 2, 3; ̸ = ) tween energy levels, atom-atom and atom-wall collisions, laser line width fluctuation, transit time broadening, spin exchange collisions, etc. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

Light storage for one second in room-temperature alkali vapor

“…Rare isotopes of noble gases, such as helium-3, carry nuclear spins that are optically inaccessible and exhibit coherence times on the scale of hours [27]. It has been demonstrated that spin-exchange collisions can coherently couple the orientation moment of two alkali species [28,29] as well as the orientation moment of alkali and rare-gas atoms [30], while all other spin moments are relaxed. Mapping light onto spin orientation thus not only protects the stored information from self spin-exchange relaxation, but also enables its transfer from one spin ensemble to another.…”

Spin noise correlations in multispecies hot atomic vapors

“…Bloch Equations can be also used to model the exchange dynamics of electronic spin polarization between two atomic species. In the case of unpolarized vapors, an interesting effect of spin noise exchange between 85 Rb and 87 Rb has been reported in [100] and is revealed as an increase of the spin noise power at low magnetic fields, reflecting a correlation build-up as a consequence of strong cross-exchange. At higher magnetic fields, the fast spin precession averages out the exchange correlations.…”

“…Deeper understanding of spin noise and its relation to the collisional relaxation processes [85][86][87] paves the way towards improving quantum enhanced metrology in hot vapor systems [88][89][90][91]. Some of the modern applications of spin noise spectroscopy in hot vapors are: measurement of zero-field spin noise using magnetic pulses [92], measurement of higher order spin noise like alignment noise [93,94], spin noise measurements with time-dependent magnetic fields [95,96], demonstration of quantum random number generator using spin noise [97], effects of atomic diffusion on the spin noise spectrum [98,99] and dual-species spin noise measurements [100][101][102][103][104].…”