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Related Concept Videos

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

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

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

Spin–Spin Coupling: One-Bond Coupling

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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,...
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Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

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

1.3K
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.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
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Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

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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...
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Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

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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...
1.2K
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

3.4K
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...
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Generation and Coherent Control of Pulsed Quantum Frequency Combs
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Electrically controlled eight-spin-qubit entangled-state generation in a molecular break junction.

Mausumi Chattopadhyaya1, Md Mehboob Alam, Debasis Sarkar

  • 1Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Kolkata-700009 (India).

Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry
|April 26, 2014
PubMed
Summary

Researchers demonstrate the first electrical generation of an eight-qubit entangled state using a dinuclear iron complex. This breakthrough in quantum computing utilizes a molecular break junction and preserves spin states with specific electric field limits.

Keywords:
entanglementnon-equilibrium Green′s functionquantum interferencequantum transportspin-qubits

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Area of Science:

  • Quantum Computing
  • Molecular Spintronics
  • Quantum Entanglement

Background:

  • Generating multi-qubit entangled states, particularly using electric fields, is a significant challenge in quantum computing.
  • Existing methods for creating entangled states are limited, and electrical control remains elusive.

Purpose of the Study:

  • To report the first successful generation of an eight-spin-qubit entangled state using only electrical means.
  • To investigate the feasibility of using a dinuclear Fe(II) complex in a molecular break junction for quantum entanglement.

Main Methods:

  • Employed non-equilibrium Green's function (NEGF) based quantum-transport calculations.
  • Integrated non-collinear spin density functional theory (SCDFT) with NEGF for accurate spin dynamics.
  • Simulated the system within a molecular break junction setup.

Main Results:

  • Successfully generated an eight-spin-qubit entangled state from the high-spin state of a dinuclear Fe(II) complex.
  • Addressed critical aspects such as gate operation schemes, gating times, and decoherence.
  • Determined that the high-spin state is preserved below an electric field strength of 0.78 V nm⁻¹.

Conclusions:

  • Presents a novel method for achieving multi-qubit entanglement purely through electrical control.
  • Highlights the potential of molecular systems, specifically dinuclear Fe(II) complexes, in advancing electrical quantum information processing.
  • Offers a viable pathway for experimental realization of electrically generated entangled states.