Related Experiment Video
Updated: Jun 21, 2026
10:00
Gradient Echo Quantum Memory in Warm Atomic Vapor
Published on: November 11, 2013
Qubit protection in nuclear-spin quantum dot memories
Z Kurucz1, M W Sørensen, J M Taylor
1Fachbereich Physik, University of Kaiserslautern, D-67663 Kaiserslautern, Germany.
Physical Review Letters
|August 8, 2009
Summary
We developed a method to protect quantum information in semiconductor quantum dots. By making the nuclear spin interaction off-resonant, an energy gap shields quantum memory from noise.
Area of Science:
- Quantum Information Science
- Semiconductor Spintronics
- Quantum Computing Hardware
Background:
- Quantum information is fragile and susceptible to environmental noise.
- Nuclear spins in semiconductor quantum dots are a promising platform for quantum memory.
- Hyperfine coupling between electron and nuclear spins is a key interaction.
Purpose of the Study:
- To propose and analyze a mechanism for protecting quantum information stored in nuclear spins.
- To investigate the role of hyperfine coupling in quantum memory stability.
- To demonstrate noise resilience through engineered energy gaps.
Main Methods:
- Theoretical analysis of spin dynamics in a semiconductor quantum dot.
- Investigating the effect of off-resonant hyperfine coupling.
- Modeling protection against spin-flip and spin-dephasing noise.
Main Results:
- An off-resonant hyperfine coupling creates an energy gap for collective nuclear spin states.
- This energy gap effectively isolates the quantum memory from local noise.
- The mechanism shows robustness against imperfect initial spin polarization and inhomogeneous coupling.
Conclusions:
- Engineered off-resonant hyperfine coupling provides a viable protection mechanism for quantum memory.
- This approach enhances the stability and fidelity of quantum information stored in nuclear spins.
- The findings contribute to the development of robust quantum computing architectures.
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...
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...
01:14Atomic 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.
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...
00:59Atomic Nuclei: Nuclear Magnetic Moment
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
01:05Atomic Nuclei: Magnetic Resonance
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...