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Related Concept Videos

Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic 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...
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
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Related Experiment Video

Updated: Jun 5, 2026

Generation and Coherent Control of Pulsed Quantum Frequency Combs
06:42

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Published on: June 8, 2018

Strongly enhanced spin squeezing via quantum control.

Collin M Trail1, Poul S Jessen, Ivan H Deutsch

  • 1Center for Quantum Information and Control (CQuIC) and Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico, USA. ctrail@unm.edu

Physical Review Letters
|January 15, 2011
PubMed
Summary
This summary is machine-generated.

We introduce a novel spin squeezing technique using a double-pass Faraday interaction. This method enhances quantum entanglement for improved precision measurements, achieving approximately 10 dB squeezing.

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Area of Science:

  • Atomic physics
  • Quantum optics
  • Quantum information science

Background:

  • Spin squeezing is crucial for enhancing measurement precision beyond the standard quantum limit.
  • Previous methods often struggle with decoherence and technical limitations.
  • Optical probes interacting with atomic ensembles are key to many quantum technologies.

Purpose of the Study:

  • To develop a new, robust method for generating spin squeezing.
  • To theoretically model the enhancement of spin squeezing via a specific optical-atom interaction.
  • To assess the practical feasibility and potential squeezing levels achievable with laboratory parameters.

Main Methods:

  • Utilizing a double-pass Faraday interaction between an optical probe and an optically dense atomic sample.
  • Employing a quantum eraser to eliminate residual spin-probe entanglement.
  • Implementing a single-axis twisting unitary map on the collective spin.
  • Phase matching the interaction for exponential squeezing enhancement.

Main Results:

  • Demonstrated exponential enhancement of spin squeezing with increasing optical density for short interaction times.
  • Modeled the impact of decoherence, technical loss, and noise on squeezing.
  • Predicted achievable squeezing levels of approximately 10 dB with current laboratory parameters.

Conclusions:

  • The proposed double-pass Faraday interaction offers a promising route to significant spin squeezing.
  • The technique shows potential for practical applications requiring high-precision measurements.
  • Further research should focus on mitigating decoherence and technical imperfections to maximize squeezing.