Related Experiment Video
Updated: Jul 6, 2026
07:56
A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Highly entangled ground States in tripartite qubit systems.
Beat Röthlisberger1, Jörg Lehmann, D S Saraga
1Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Physical Review Letters
|March 21, 2008
Summary
Researchers created highly entangled ground states in three coupled qubits using specific magnetic fields. They efficiently calculated entanglement at finite temperatures, identifying conditions for maximum entanglement in this quantum system.
Area of Science:
- Quantum Information Science
- Condensed Matter Physics
Background:
- Investigating entangled states in multi-qubit systems is crucial for quantum computing.
- Understanding ground states and their entanglement properties is key to developing robust quantum devices.
Purpose of the Study:
- To explore the creation of highly entangled ground states in a three-qubit system arranged in a ring.
- To identify magnetic field configurations that produce specific entangled states, like Greenberger-Horne-Zeilinger (GHZ) and W states.
- To analyze entanglement at finite temperatures using the mixed-state tangle (tau).
Main Methods:
- Utilizing a system of three exchange-coupled qubits in a ring geometry.
- Identifying suitable magnetic field configurations for targeted entangled states.
- Employing a generalized conjugate gradient optimization algorithm to calculate the mixed-state tangle (tau).
Main Results:
- Successfully identified magnetic field configurations for approximate Greenberger-Horne-Zeilinger (GHZ) and exact W ground states.
- Demonstrated efficient and high-precision calculation of mixed-state tangle (tau) at finite temperatures.
- Determined the specific parameter regime where the tripartite system achieves maximum equilibrium entanglement.
Conclusions:
- The study provides a method for creating and quantifying entanglement in a three-qubit system.
- Efficient calculation of entanglement is possible even at finite temperatures, crucial for practical quantum applications.
- The identified parameter regimes offer pathways for maximizing entanglement in similar quantum systems.
Related Concept Videos
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...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:45Valence Bond Theory
Overview of Valence Bond Theory
03:06The Pauli Exclusion Principle
The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that contains three pieces of information:
01:22Spin–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.
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 involved orbitals. The...
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 involved orbitals. The...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.