Synopsis: Outsmarting decoherence in a trapped ion quantum computer

Ion traps can store quantum information with long coherence times and support universal quantum computations.
Synopsis figure
Illustration: T. Monz et al., Phys. Rev. Lett. (2009)

Decoherence is the adversary of quantum information processing since it destroys the fragile superpositions where information is stored. One method to circumvent the loss of coherence is to identify and encode quantum information in special subspaces of the Hilbert space, called decoherence-free subspaces, which can yield a factor of 100 increase in coherence times.

Still, these special subspaces will only be as useful as the computations they permit. Writing in Physical Review Letters, Thomas Monz, Kihwan Kim, and colleagues at Universität Innsbruck and Österreichische Akademie der Wissenschaften in Austria show they can successfully perform universal quantum computational operations within a decoherence-free subspace based on an array of trapped calcium ions. They encode quantum information in two electronic states on each ion, and the decoherence-free subspace is obtained by using two ions to represent one logical qubit state, resulting in a system that is robust against dephasing errors.

Monz et al. are able to perform a number of operations in the calcium array, including qubit rotations, a two-qubit phase gate, and a combination of the two for making a controlled-NOT gate. This is the first ion trap demonstration of a set of logical gates that are universal for quantum computation and exist within a decoherence-free subspace.

Sonja Grondalski


Announcements

More Announcements »

Subject Areas

Atomic and Molecular PhysicsQuantum Information

Previous Synopsis

Quantum Information

Eliminating charge noise

Read More »

Next Synopsis

Superconductivity

A clean slate

Read More »

Related Articles

Synopsis: Dipolar Gas Chilled to Near Zero
Atomic and Molecular Physics

Synopsis: Dipolar Gas Chilled to Near Zero

The cooling of strongly dipolar molecules to their absolute ground state has opened the possibility of creating new forms of matter. Read More »

Synopsis: Nanofiber Optical Memory
Quantum Information

Synopsis: Nanofiber Optical Memory

Light signals propagating down an ultrathin fiber can be temporarily stored in a cloud of cold atoms surrounding the fiber. Read More »

Synopsis: Rapid Alignment
Atomic and Molecular Physics

Synopsis: Rapid Alignment

A frequency comb can align an ensemble of molecules 150 million times per second. Read More »

More Articles