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:2208.12805 · Physical Review A

Measurement of Rb-Rb van der Waals coefficient via quantum diffractive universality

Riley A. Stewart, Pinrui Shen, James L. Booth, Kirk W. Madison

Published Nov 30, 2022• 11 citations
arXivHTMLPDF

Abstract

The authors demonstrate a new method for measuring the C${}_{6}$ van der Waals coefficient of the Rb-Rb interaction potential from the loss rate of atoms confined in a shallow atom trap of tunable depth. The technique is based on the universal nature of the room-temperature collisions, which depends only on the long-range potential between the collision partners.

DOI
10.1103/physreva.106.052812

Related papers

Trap-depth determination from residual gas collisions

Janelle Van Dongen, Chenchong Zhu, D. Clement +3 more

We present a method for determining the depth of an atomic or molecular trap of any type. This method relies on a measurement of the trap loss rate induced by collisions with background gas particles. Given a fixed gas composition, the loss rate uniquely determines the trap depth. Because of the ``soft'' long-range nature of the van der Waals interaction, these collisions transfer kinetic energy to trapped particles across a broad range of energy scales, from room temperature to the microkelvin energy scale. The resulting loss rate therefore exhibits a significant variation over an enormous range of trap depths, making this technique a powerful diagnostic with a large dynamic range. We present trap depth measurements of a Rb magneto-optical trap using this method and a different technique that relies on measurements of loss rates during optical excitation of colliding atoms to a repulsive molecular state. The main advantage of the method presented here is its large dynamic range and applicability to traps of any type requiring only knowledge of the background gas density and the interaction potential between the trapped and background gas particles.

Physical Review A•Aug 16, 2011•27 citations

Revising the universality hypothesis for room-temperature collisions

James L. Booth, Kirk W. Madison

Atoms constitute promising quantum sensors for a variety of scenarios including vacuum metrology. Key to this application is knowledge of the collision rate coefficient of the sensor atom with the particles being detected. Prior work demonstrated that, for room-temperature collisions, the total collision rate coefficient and the trap depth dependence of the sensor atom loss rate from shallow traps are both universal, independent of the interaction potential at short range. It was also shown that measurements of the energy transferred to the sensor atom by the collision can be used to estimate the total collision rate coefficient. However, discrepancies found when comparing the results of this and other methods of deducing the rate coefficient call into question its accuracy. Here the universality hypothesis is reexamined and an important correction is presented. We find that measurements of the postcollision recoil energy of sensor atoms held in shallow magnetic traps only provide information about the interaction potential at the very largest interatomic distances (e.g., the value of ${C}_{6}$ for a leading order term of $\ensuremath{-}{C}_{6}/{r}^{6}$). As other non-negligible terms exist at medium and long ranges, the total collision rate coefficient, even if universal, can differ from that computed solely from the value of ${C}_{6}$. By incorporating these other long-range terms into a simple semiclassical (SC) calculation, we find the SC prediction matches that of full, multichannel, quantum mechanical scattering calculations using the complete potential. This work resolves the discrepancies, demonstrates the simplicity of estimating the rate coefficients for universal collision partners, and provides guidance for using atoms as a self-calibrating primary quantum pressure standard.

arXiv:2406.17065•Physical Review A•Nov 4, 2024•3 citations

Universality of Diffractive Collisions and the Quantum Pressure Standard

James L. Booth, Pinrui Shen, Roman V. Krems +1 more

This work demonstrates that quantum diffractive collisions, those that result in very small momentum and energy transfer, are universal. Specifically, the cumulative energy distribution transferred to an initially stationary sensor particle by a quantum diffractive collision follows a universal function that depends only on the sensor particle mass and the thermally-averaged, total collision cross section. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined {\it only} by the analytic form of the interaction potential at long range. Using cold $^{87}$Rb sensor atoms confined in a magnetic trap, we observe experimentally the universal function specific to van der Waals collisions, and realize a \emph{self-defining} particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a key advance for vacuum and pressure metrology. The quantum pressure standard realized here was compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N$_2$. The pressure measurements agreed at the 0.5\% level.

arXiv:1905.02193•May 3, 2019•0 citations

Universal relations between atomic dipolar relaxation and van der Waals interaction

Yuangang Deng, Yi-Quan Zou, Gao‐Ren Wang +4 more

Dipolar relaxation happens when one or both colliding atoms flip their spins exothermically inside a magnetic ($B$) field. This work reports precise measurements of dipolar relaxation in a Bose-Einstein condensate of ground state $^{87}$Rb atoms together with in-depth theoretical investigations. Previous perturbative treatments fail to explain our observations except at very small $B$-fields. By employing quantum defect theory based on analytic solutions of asymptotic van der Waals interaction $-C_6/R^6$ ($R$ being interatomic spacing), we significantly expand the applicable range of perturbative treatment. We find the $B$-dependent dipolar relaxation lineshapes are largely universal, determined by the coefficient $C_6$ and the associated $s$-wave scattering lengths $a_{\rm sc}$ of the states before and after spin flips. This universality, which applies generally to other atomic species as well, implicates potential controls of dipolar relaxation and related cold chemical reactions by tuning $a_{\rm sc}$.

arXiv:2101.11323•Jan 27, 2021•1 citation

Universality of quantum diffractive collisions and the quantum pressure standard

James L. Booth, Pinrui Shen, Roman V. Krems +1 more

Abstract This work demonstrates that quantum diffractive collisions are governed by a universal law characterized by a single parameter that can be determined experimentally. Specifically, we report a quantitative form of the universal, cumulative energy distribution transferred to initially stationary sensor particles by quantum diffractive collisions. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined only by the analytic form of the interaction potential at long range. Using cold 87Rb sensor atoms confined in a magnetic trap, we observe experimentally p QDU 6 , the universal function specific to van der Waals collisions, and use it to realize a self-defining particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a fundamental advance for vacuum and pressure metrology. The quantum pressure standard realized here is compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N2. The pressure measurements agree at the 0.5% level.

New Journal of Physics•Sep 18, 2019•26 citations

Tests of Universal Three-Body Physics in an Ultracold Bose-Fermi Mixture

Ruth Bloom, Ming-Guang Hu, Tyler D. Cumby +1 more

Recent measurements of Efimov resonances for a number of ultracold atom species have revealed an unexpected universality, in which three-body scattering properties are determined by the van der Waals length of the two-body interaction potential. To investigate whether this universality extends to heteronuclear mixtures, we measure loss rate coefficients in an ultracold trapped gas of 40K and 87Rb atoms. We find an Efimov-like resonance in the rate of inelastic collisions between 40K87Rb Feshbach molecules and 87Rb atoms. However, we do not observe any Efimov-related resonances in the rates of inelastic collisions between three atoms. These observations are compared to previous measurements by the LENS group of Efimov resonances in a 41K and 87Rb mixture as well as to recent predictions.

arXiv:1304.6989•Physical Review Letters•Sep 3, 2013•121 citations
The authors demonstrate a new method for measuring the C6{}_{6}6​ van der Waals coefficient of the Rb-Rb interaction potential from the loss rate of atoms confined in a shallow atom trap of tunable depth. The technique is based on the universal nature of the room-temperature collisions, which depends only on the long-range potential between the collision partners.
We present a method for determining the depth of an atomic or molecular trap of any type. This method relies on a measurement of the trap loss rate induced by collisions with background gas particles. Given a fixed gas composition, the loss rate uniquely determines the trap depth. Because of the ``soft'' long-range nature of the van der Waals interaction, these collisions transfer kinetic energy to trapped particles across a broad range of energy scales, from room temperature to the microkelvin energy scale. The resulting loss rate therefore exhibits a significant variation over an enormous range of trap depths, making this technique a powerful diagnostic with a large dynamic range. We present trap depth measurements of a Rb magneto-optical trap using this method and a different technique that relies on measurements of loss rates during optical excitation of colliding atoms to a repulsive molecular state. The main advantage of the method presented here is its large dynamic range and applicability to traps of any type requiring only knowledge of the background gas density and the interaction potential between the trapped and background gas particles.
Atoms constitute promising quantum sensors for a variety of scenarios including vacuum metrology. Key to this application is knowledge of the collision rate coefficient of the sensor atom with the particles being detected. Prior work demonstrated that, for room-temperature collisions, the total collision rate coefficient and the trap depth dependence of the sensor atom loss rate from shallow traps are both universal, independent of the interaction potential at short range. It was also shown that measurements of the energy transferred to the sensor atom by the collision can be used to estimate the total collision rate coefficient. However, discrepancies found when comparing the results of this and other methods of deducing the rate coefficient call into question its accuracy. Here the universality hypothesis is reexamined and an important correction is presented. We find that measurements of the postcollision recoil energy of sensor atoms held in shallow magnetic traps only provide information about the interaction potential at the very largest interatomic distances (e.g., the value of C6{C}_{6}C6​ for a leading order term of $\ensuremath{-}{C}_{6}/{r}^{6}$). As other non-negligible terms exist at medium and long ranges, the total collision rate coefficient, even if universal, can differ from that computed solely from the value of C6{C}_{6}C6​. By incorporating these other long-range terms into a simple semiclassical (SC) calculation, we find the SC prediction matches that of full, multichannel, quantum mechanical scattering calculations using the complete potential. This work resolves the discrepancies, demonstrates the simplicity of estimating the rate coefficients for universal collision partners, and provides guidance for using atoms as a self-calibrating primary quantum pressure standard.
This work demonstrates that quantum diffractive collisions, those that result in very small momentum and energy transfer, are universal. Specifically, the cumulative energy distribution transferred to an initially stationary sensor particle by a quantum diffractive collision follows a universal function that depends only on the sensor particle mass and the thermally-averaged, total collision cross section. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined {\it only} by the analytic form of the interaction potential at long range. Using cold 87^{87}87Rb sensor atoms confined in a magnetic trap, we observe experimentally the universal function specific to van der Waals collisions, and realize a \emph{self-defining} particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a key advance for vacuum and pressure metrology. The quantum pressure standard realized here was compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N2_22​. The pressure measurements agreed at the 0.5\% level.
Dipolar relaxation happens when one or both colliding atoms flip their spins exothermically inside a magnetic (BBB) field. This work reports precise measurements of dipolar relaxation in a Bose-Einstein condensate of ground state 87^{87}87Rb atoms together with in-depth theoretical investigations. Previous perturbative treatments fail to explain our observations except at very small BBB-fields. By employing quantum defect theory based on analytic solutions of asymptotic van der Waals interaction −C6/R6-C_6/R^6−C6​/R6 (RRR being interatomic spacing), we significantly expand the applicable range of perturbative treatment. We find the BBB-dependent dipolar relaxation lineshapes are largely universal, determined by the coefficient C6C_6C6​ and the associated sss-wave scattering lengths asca_{\rm sc}asc​ of the states before and after spin flips. This universality, which applies generally to other atomic species as well, implicates potential controls of dipolar relaxation and related cold chemical reactions by tuning asca_{\rm sc}asc​.
Abstract This work demonstrates that quantum diffractive collisions are governed by a universal law characterized by a single parameter that can be determined experimentally. Specifically, we report a quantitative form of the universal, cumulative energy distribution transferred to initially stationary sensor particles by quantum diffractive collisions. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined only by the analytic form of the interaction potential at long range. Using cold 87Rb sensor atoms confined in a magnetic trap, we observe experimentally p QDU 6 , the universal function specific to van der Waals collisions, and use it to realize a self-defining particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a fundamental advance for vacuum and pressure metrology. The quantum pressure standard realized here is compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N2. The pressure measurements agree at the 0.5% level.
Recent measurements of Efimov resonances for a number of ultracold atom species have revealed an unexpected universality, in which three-body scattering properties are determined by the van der Waals length of the two-body interaction potential. To investigate whether this universality extends to heteronuclear mixtures, we measure loss rate coefficients in an ultracold trapped gas of 40K and 87Rb atoms. We find an Efimov-like resonance in the rate of inelastic collisions between 40K87Rb Feshbach molecules and 87Rb atoms. However, we do not observe any Efimov-related resonances in the rates of inelastic collisions between three atoms. These observations are compared to previous measurements by the LENS group of Efimov resonances in a 41K and 87Rb mixture as well as to recent predictions.