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Related Concept Videos

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
Group Polarization01:01

Group Polarization

Group polarization is the strengthening of an original group attitude following the discussion of views within a group (Teger & Pruitt, 1967). That is, if a group initially favors a viewpoint, after discussion the group consensus is likely a stronger endorsement of the viewpoint. Conversely, if the group was initially opposed to a viewpoint, group discussion would likely lead to stronger opposition.
¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
Potential Due to a Polarized Object01:29

Potential Due to a Polarized Object

A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
Double Resonance Techniques: Overview01:12

Double 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...
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)01:15

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...

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Related Experiment Video

Updated: Jul 16, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
07:56

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Experimental long-distance decoy-state quantum key distribution based on polarization encoding.

Cheng-Zhi Peng1, Jun Zhang, Dong Yang

  • 1Department of Physics, Tsinghua University, Beijing, China.

Physical Review Letters
|March 16, 2007
PubMed
Summary

Researchers demonstrated decoy-state quantum key distribution (QKD) over 102 km using one-way communication. A simplified setup with one detector achieved secure QKD over 75 km, enhancing security against detector inefficiencies.

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Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
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Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

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Last Updated: Jul 16, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
07:56

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
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Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Published on: May 30, 2014

Area of Science:

  • Quantum Information Science
  • Quantum Cryptography
  • Optical Communication

Background:

  • Quantum Key Distribution (QKD) offers secure communication based on quantum mechanics principles.
  • Decoy-state QKD protocols are crucial for enhancing security against photon number splitting attacks.
  • Long-distance fiber optic implementations face challenges like polarization mode dispersion and detector efficiency mismatch.

Purpose of the Study:

  • To demonstrate decoy-state QKD with one-way quantum communication over extended fiber optic links.
  • To simplify the experimental setup for practical and secure QKD implementation.
  • To address and overcome security loopholes related to detector efficiency mismatch.

Main Methods:

  • Utilized decoy-state QKD protocol with three light source intensities (0, 0.2, 0.6).
  • Implemented one-way quantum communication in polarization space.
  • Employed an automatic polarization compensation system for active compensation of polarization mode dispersion.
  • Simplified the setup using a single detector for enhanced security and reduced complexity.

Main Results:

  • Successfully demonstrated decoy-state QKD over a 102 km optical fiber link.
  • Achieved a simplified and secure one-way decoy-state QKD over a 75 km link using a single detector.
  • Overcame security loopholes associated with detector efficiency mismatch.
  • Generated unconditionally secure final keys.

Conclusions:

  • The demonstrated experimental setup provides a practical and secure method for long-distance quantum key distribution.
  • Simplifying the QKD system with fewer detectors enhances security and feasibility.
  • Active polarization compensation is vital for maintaining signal integrity in long-haul fiber optic QKD.