Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1105.0143 · Physical Review A

Coherent control of ultracold Rb85 trap-loss collisions with nonlinearly frequency-chirped light

J. A. Pechkis, J. L. Carini, C. E. Rogers, P. L. Gould, Shimshon Kallush, Ronnie Kosloff

Published Jun 6, 2011• 22 citations
arXivHTMLPDF

Abstract

We present results on coherent control of ultracold trap-loss collisions using 40-ns pulses of nonlinearly frequency-chirped light. The chirps, either positive or negative, sweep $~$1 GHz in 100 ns and are centered at various detunings below the ${D}_{2}$ line of $^{85}\mathrm{Rb}$. At each center detuning, we compare the collisional rate constant $\ensuremath{\beta}$ for chirps that are linear in time, concave-down, and concave-up. For positive chirps, we find that $\ensuremath{\beta}$ generally depends very little on the shape of the chirp. For negative chirps, however, we find that $\ensuremath{\beta}$ can be enhanced by up to 50(20)$%$ for the case of the concave-down shape. This occurs at detunings where the evolution of the wave packet is expected to be coherent. An enhancement at these detunings is also seen in quantum-mechanical simulations of the collisional process.

DOI
10.1103/physreva.83.063403

Related papers

Coherent Control of Trap-Loss Collisions and Molecule Formation with Frequency-Chirped Light

J. A. Pechkis

We present results on coherent control of ultracold trap-loss collisions and molecule formation using frequency-chirped light. The chirps, either positive or negative, sweep 1 GHz in 100 ns and are red-detuned below the D2 line in either 85Rb or 87Rb. The pulses are Gaussian and have a full-width at half-maximum (FWHM) of 40 ns. In our collision experiments, we demonstrate coherent control of ultracold 85Rb collisions using nonlinear (either concave-down or concave-up) frequency chirps in the region of pulse detunings where coherent collision blocking occurs. We attribute this to the excitation radius of the negative chirp following the excited-wavepacket trajectory. We find that this process is dependent on the nonlinearity of the negative chirp. Specifically, the concave-down negative chirp yields a higher value of the collisional loss rate constant β than those of the concave-up and linear negative chirps. For nonlinear positive chirps, we find no significant dependence of β on the nonlinearity of the chirp. Our measurements are supported by quantum mechanical simulations of the collisional process. ^ In our molecule formation experiments, we use resonantly-enhanced multi- photon ionization to directly detect ground-state 87Rb 2 formed though photoassociation (PA) by linearly frequency-chirped pulses and subsequent spontaneous decay. In particular, we measure the rates of formation (R) and photodestruction (Γ PD) for positive and negative frequency-chirped pulses, as well as for unchirped pulses. We find that the unchirped pulse yields higher values of both R and ΓPD than those of the positively-chirped pulse, whose values in turn are greater than those of the negatively-chirped pulse. Our results are important steps towards coherent control of ultracold ground-state molecule formation. ^

•Jan 1, 2010•0 citations

Quantum dynamical calculations of ultracold collisions induced by nonlinearly chirped light

J. L. Carini, J. A. Pechkis, C. E. Rogers +3 more

We describe quantum dynamical calculations of ultracold ${}^{85}$Rb trap-loss collisions induced by pulses of light whose frequency is chirped on the nanosecond time scale. The chirped light excites the ground-state collisional wave function to the long-range attractive potential and escape from the trap is modeled by an absorbing boundary at short range. Both positive and negative chirps are considered and various chirp shapes and detunings are examined. For positive chirps, the loss rates are rather independent of the chirp shape. Negative chirps, on the other hand, show a dependence on chirp shape for detunings where collisional flux can be coherently returned to the ground state. These trends are consistent with the results of a recent experiment.

Physical Review A•Jan 31, 2012•9 citations

Coherent control of ultracold collisions with chirped light: Direction matters

Matthew J. Wright, J. A. Pechkis, J. L. Carini +3 more

We demonstrate the ability to coherently control ultracold atomic Rb collisions using frequency-chirped light on the nanosecond time scale. For certain center frequencies of the chirp, the rate of inelastic trap-loss collisions induced by negatively chirped light is dramatically suppressed compared to the case of a positive chirp. We attribute this to a fundamental asymmetry in the system: an excited wave packet moves inward on the attractive molecular potential. For a positive chirp, the resonance condition moves outward in time, while for a negative chirp, it moves inward, in the same direction as the excited wave packet; this allows multiple interactions between the wave packet and the light, enabling the wave packet to be returned coherently to the ground state. Classical and quantum calculations support this interpretation.

arXiv:physics/0612071•Physical Review A•May 3, 2007•41 citations

Probing ultracold collisional dynamics with frequency-chirped pulses

Matthew J. Wright, J. A. Pechkis, J. L. Carini +1 more

We report on the dynamics of ultracold collisions induced by near-resonant frequency-chirped light. A series of identical chirped pulses, separated by a variable delay, is applied to an ultracold sample of $^{85}\mathrm{Rb}$, and the rate of inelastic trap-loss collisions is measured. For small detunings of the chirped light below the atomic resonance, we observe that the rate of collisions induced by a given pulse can be increased by the presence of an earlier pulse. We attribute this to the enhancement of short-range collisional flux by the long-range excitation of atom pairs to an attractive molecular potential. For larger detunings and short delays, we find that a leading pulse can suppress the rate of collisions caused by a following pulse. This is due to a depletion of short-range atom pairs by the earlier pulse. Comparison of our data to classical Monte Carlo simulations of the collisions yields reasonable agreement.

arXiv:physics/0611003•Physical Review A•Dec 4, 2006•14 citations

Efficient Formation of Ultracold Molecules with Chirped Nanosecond Pulses

J. L. Carini, Shimshon Kallush, Ronnie Kosloff +1 more

We describe experiments and associated quantum simulations involving the production of ultracold (87)Rb2 molecules with nanosecond pulses of frequency-chirped light. With appropriate chirp parameters, the formation is dominated by coherent processes. For a positive chirp, excited molecules are produced by photoassociation early in the chirp, and then transferred into high vibrational levels of the lowest triplet state by stimulated emission later in the chirp. Generally good agreement is seen between the data and the simulations. Shaping of the chirp can lead to a significant enhancement of the formation rate. Further improvements using higher intensities and different intermediate states are predicted.

arXiv:1510.04672•The Journal of Physical Chemistry A•Dec 11, 2015•16 citations

Control of Ultracold Collisions with Frequency-Chirped Light

Matthew J. Wright, J. A. Pechkis, J. L. Carini +2 more

We report on ultracold collision experiments utilizing frequency-chirped laser light. The collision rate is measured through trap loss. We also present our recent progress towards producing the frequency-chirp through phase modulation of the laser light.

Frontiers in Optics•Jan 1, 2006•0 citations
We present results on coherent control of ultracold trap-loss collisions using 40-ns pulses of nonlinearly frequency-chirped light. The chirps, either positive or negative, sweep  ~ 1 GHz in 100 ns and are centered at various detunings below the D2{D}_{2}D2​ line of 85Rb^{85}\mathrm{Rb}85Rb. At each center detuning, we compare the collisional rate constant \ensuremathβ\ensuremath{\beta}\ensuremathβ for chirps that are linear in time, concave-down, and concave-up. For positive chirps, we find that \ensuremathβ\ensuremath{\beta}\ensuremathβ generally depends very little on the shape of the chirp. For negative chirps, however, we find that \ensuremathβ\ensuremath{\beta}\ensuremathβ can be enhanced by up to 50(20)% for the case of the concave-down shape. This occurs at detunings where the evolution of the wave packet is expected to be coherent. An enhancement at these detunings is also seen in quantum-mechanical simulations of the collisional process.
We present results on coherent control of ultracold trap-loss collisions and molecule formation using frequency-chirped light. The chirps, either positive or negative, sweep 1 GHz in 100 ns and are red-detuned below the D2 line in either 85Rb or 87Rb. The pulses are Gaussian and have a full-width at half-maximum (FWHM) of 40 ns. In our collision experiments, we demonstrate coherent control of ultracold 85Rb collisions using nonlinear (either concave-down or concave-up) frequency chirps in the region of pulse detunings where coherent collision blocking occurs. We attribute this to the excitation radius of the negative chirp following the excited-wavepacket trajectory. We find that this process is dependent on the nonlinearity of the negative chirp. Specifically, the concave-down negative chirp yields a higher value of the collisional loss rate constant β than those of the concave-up and linear negative chirps. For nonlinear positive chirps, we find no significant dependence of β on the nonlinearity of the chirp. Our measurements are supported by quantum mechanical simulations of the collisional process. ^ In our molecule formation experiments, we use resonantly-enhanced multi- photon ionization to directly detect ground-state 87Rb 2 formed though photoassociation (PA) by linearly frequency-chirped pulses and subsequent spontaneous decay. In particular, we measure the rates of formation (R) and photodestruction (Γ PD) for positive and negative frequency-chirped pulses, as well as for unchirped pulses. We find that the unchirped pulse yields higher values of both R and ΓPD than those of the positively-chirped pulse, whose values in turn are greater than those of the negatively-chirped pulse. Our results are important steps towards coherent control of ultracold ground-state molecule formation. ^
We describe quantum dynamical calculations of ultracold 85{}^{85}85Rb trap-loss collisions induced by pulses of light whose frequency is chirped on the nanosecond time scale. The chirped light excites the ground-state collisional wave function to the long-range attractive potential and escape from the trap is modeled by an absorbing boundary at short range. Both positive and negative chirps are considered and various chirp shapes and detunings are examined. For positive chirps, the loss rates are rather independent of the chirp shape. Negative chirps, on the other hand, show a dependence on chirp shape for detunings where collisional flux can be coherently returned to the ground state. These trends are consistent with the results of a recent experiment.
We demonstrate the ability to coherently control ultracold atomic Rb collisions using frequency-chirped light on the nanosecond time scale. For certain center frequencies of the chirp, the rate of inelastic trap-loss collisions induced by negatively chirped light is dramatically suppressed compared to the case of a positive chirp. We attribute this to a fundamental asymmetry in the system: an excited wave packet moves inward on the attractive molecular potential. For a positive chirp, the resonance condition moves outward in time, while for a negative chirp, it moves inward, in the same direction as the excited wave packet; this allows multiple interactions between the wave packet and the light, enabling the wave packet to be returned coherently to the ground state. Classical and quantum calculations support this interpretation.
We report on the dynamics of ultracold collisions induced by near-resonant frequency-chirped light. A series of identical chirped pulses, separated by a variable delay, is applied to an ultracold sample of 85Rb^{85}\mathrm{Rb}85Rb, and the rate of inelastic trap-loss collisions is measured. For small detunings of the chirped light below the atomic resonance, we observe that the rate of collisions induced by a given pulse can be increased by the presence of an earlier pulse. We attribute this to the enhancement of short-range collisional flux by the long-range excitation of atom pairs to an attractive molecular potential. For larger detunings and short delays, we find that a leading pulse can suppress the rate of collisions caused by a following pulse. This is due to a depletion of short-range atom pairs by the earlier pulse. Comparison of our data to classical Monte Carlo simulations of the collisions yields reasonable agreement.
We describe experiments and associated quantum simulations involving the production of ultracold (87)Rb2 molecules with nanosecond pulses of frequency-chirped light. With appropriate chirp parameters, the formation is dominated by coherent processes. For a positive chirp, excited molecules are produced by photoassociation early in the chirp, and then transferred into high vibrational levels of the lowest triplet state by stimulated emission later in the chirp. Generally good agreement is seen between the data and the simulations. Shaping of the chirp can lead to a significant enhancement of the formation rate. Further improvements using higher intensities and different intermediate states are predicted.