Synopsis: A spin on graphene

Spins in a graphene quantum dot display properties surprisingly similar to those in semiconductor dots, but with potential for longer coherence times.
Synopsis figure
Credit: J. Güttinger et al., Phys. Rev. Lett. (2010)

Whether quantum dots will prove to be reliable building blocks for a quantum computer will depend on how well we measure and control their charge and spin. Spin qubits in quantum dots—wherein a spin-1/2 electron encodes the two bits of information—would be particularly useful if they were fine-tuned to an applied magnetic field.

Despite extensive data on the preparation, control, and readout of spins in conventional semiconductor quantum dots such as those made of GaAs, researchers continue to be intrigued by the behavior of spins in graphene. Two limiting factors—spin-orbit interactions and hyperfine splitting—that lower spin lifetimes in other materials are expected to be less prominent in graphene. Longer lifetimes, which in turn reduce decoherence, lead to more reliable devices.

In their paper in Physical Review Letters, Johannes Güttinger, Tobias Frey, Christoph Stampfer, Thomas Ihn, and Klaus Ensslin, all at ETH Zurich in Switzerland, study how spins fill up orbital states in a graphene quantum dot in the presence of out-of-plane (perpendicular) as well as in-plane (parallel) magnetic fields and find a significant deviation from the usual spin-up–spin-down sequence. Guided by measurements of the Zeeman factor for the in-plane case, the authors attribute this deviation to the strong exchange interaction in graphene quantum dots. Despite factors that range from how the gate voltage might affect different regions in the dot to how spin behavior varies with magnetic field strengths, this study of spins in graphene takes us a step further towards graphene quantum computers. – Sami Mitra


Features

More Features »

Announcements

More Announcements »

Subject Areas

Quantum InformationGrapheneSpintronics

Previous Synopsis

Superconductivity

Unconventional pairs

Read More »

Next Synopsis

Materials Science

Cracking the case on fracture

Read More »

Related Articles

Synopsis: Entangled Photon Source Ticks All Boxes
Quantum Physics

Synopsis: Entangled Photon Source Ticks All Boxes

A quantum-dot-based device combines all of the attributes necessary for producing a reliable source of entangled photons for quantum information applications.  Read More »

Viewpoint: Alkaline Atoms Held with Optical Tweezers
Quantum Information

Viewpoint: Alkaline Atoms Held with Optical Tweezers

Three separate groups demonstrate the trapping of two-electron atoms in arrays of optical tweezers, opening up new opportunities for quantum simulation and many-body studies. Read More »

Synopsis: A Possible Quantum Computing Boost 
Quantum Information

Synopsis: A Possible Quantum Computing Boost 

A hybrid quantum-classical computing algorithm could solve a basic computer science problem faster than a classical computer. Read More »

More Articles