Related Experiment Video
Updated: Jun 8, 2026
10:00
Gradient Echo Quantum Memory in Warm Atomic Vapor
Published on: November 11, 2013
Spin self-rephasing and very long coherence times in a trapped atomic ensemble
C Deutsch1, F Ramirez-Martinez, C Lacroûte
1Laboratoire Kastler Brossel, ENS, UPMC, CNRS, 24 rue Lhomond, 75005 Paris, France.
Physical Review Letters
|September 28, 2010
Summary
Ultracold atoms exhibit surprisingly long Ramsey spectroscopy decay times due to a novel spin self-rephasing mechanism. This effect, driven by particle indistinguishability, enhances coherence in quantum systems.
Area of Science:
- Atomic physics
- Quantum optics
- Condensed matter physics
Background:
- Ramsey spectroscopy is a key technique for measuring atomic properties.
- Magnetic trapping on a chip confines ultracold atoms for precision measurements.
- Field inhomogeneities typically limit coherence times in such systems.
Purpose of the Study:
- To investigate the unexpectedly long coherence times observed in Ramsey spectroscopy of ultracold Rubidium-87 atoms.
- To explain the observed decay times exceeding theoretical limits imposed by field inhomogeneities.
- To elucidate the underlying physical mechanism responsible for enhanced coherence.
Main Methods:
- Performing Ramsey spectroscopy on ground-state ultracold Rubidium-87 atoms.
- Utilizing magnetic trapping on a chip in the Knudsen regime.
- Developing a theoretical model for spin self-rephasing due to particle indistinguishability.
Main Results:
- Observed Ramsey spectroscopy decay times of 58 ± 12 seconds, significantly longer than the expected 3 seconds.
- Identified a spin self-rephasing mechanism as the cause of the extended coherence.
- The mechanism originates from the identical spin rotation effect due to particle indistinguishability.
Conclusions:
- Particle indistinguishability can lead to spin self-rephasing, synchronizing atomic spins and extending coherence times.
- The proposed theory accurately predicts the observed experimental results.
- This spin synchronization phenomenon is general and potentially applicable to other quantum systems.
Related Concept Videos
01:28Atomic Nuclei: Types of Nuclear Relaxation
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:12Double Resonance Techniques: Overview
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
01:03Atomic Nuclei: Nuclear Spin State Overview
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
01:11Atomic Nuclei: Larmor Precession Frequency
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...
01:08Atomic Nuclei: Nuclear Spin
All atomic particles possess an intrinsic angular momentum, or 'spin'. Electrons, protons, and neutrons each have a spin value of ½, although protons and neutrons in nuclei may have higher half-integer spins owing to energetic factors.
Atomic nuclei have a net nuclear spin, , which can have an integer or half-integer value. In atomic nuclei, the spins of protons are paired against each other but not with neutrons, and vice versa. Consequently, an even number of protons does not contribute to...
Atomic nuclei have a net nuclear spin, , which can have an integer or half-integer value. In atomic nuclei, the spins of protons are paired against each other but not with neutrons, and vice versa. Consequently, an even number of protons does not contribute to...