Synopsis

Opening the gate to quantum computation

Physics 3, s9
The demonstration of entanglement between two neutral atoms would be a key step toward using them for quantum computation.
L. Isenhower et al., Phys. Rev. Lett (2010)

Entanglement lies at the heart of quantum computation. Entangling neutral atoms is attractive because they interact weakly with their environment, but by the same token, they are difficult to entangle compared with strongly interacting ions. Papers appearing simultaneously in Physical Review Letters demonstrate how separate groups are achieving entanglement between two neutral atoms by using a method called Rydberg blockade.

The underlying idea behind Rydberg blockade is that the state of one atom (the control) determines whether the other (the target) can be excited into a high-energy state. This effective coupling between the two atoms turns them into a collectively two-level system.

Tatjana Wilk and colleagues at the Institut d’Optique (CNRS and Université Paris-Sud) in France use the Rydberg blockade to entangle 87Rb atoms that are held a few microns apart by optical tweezers. In a separate paper, Larry Isenhower and colleagues at the University of Wisconsin, US, report similar methods to create a two-qubit controlled-NOT (CNOT) gate between 87Rb atoms. The CNOT gate then serves as a means to achieve entanglement between the atoms.

Both groups report the preparation of quantum states with an accuracy (or, fidelity) that is near the threshold needed to prove entanglement; correcting for losses associated with atoms that fell out of the optical traps suggests that the remaining pairs of atoms are entangled with a fidelity well over the threshold. Although there is still work to be done in fine tuning the methods reported by both groups, the papers collectively show important progress toward quantum processing with neutral atoms. – Jessica Thomas and Sonja Grondalski


Subject Areas

Atomic and Molecular PhysicsQuantum Information

Related Articles

Far Fewer Qubits Required for “Quantum Memory” Quantum Computers
Quantum Information

Far Fewer Qubits Required for “Quantum Memory” Quantum Computers

Incorporating storage units for quantum information into quantum computers may allow researchers to build such devices with several orders of magnitude fewer qubits in their processors. Read More »

Turning On a Light Beam with a Single Molecule
Quantum Information

Turning On a Light Beam with a Single Molecule

A single molecule can switch a beam of photons on or off, a potentially useful function for a quantum computer. Read More »

Turning a Quantum Computer into a Time Crystal
Quantum Information

Turning a Quantum Computer into a Time Crystal

Google’s Sycamore quantum processor can simulate an elusive quantum system called a discrete time crystal. Read More »

More Articles