Synopsis: Putting the squeeze on many atoms

Squeezed states can enhance the sensitivity of a detector and the storage capability of quantum memory devices. Because these features improve with an increase in system size, researchers are exploring ways to produce squeezed states in large ensembles of atoms.
Synopsis figure

In quantum mechanics, a squeezed state is characterized by two noncommuting observables, where one observable has a small variance at the expense of a large variance in the other, so that the uncertainty principle is satisfied. There is currently interest in preparing macroscopic squeezed states as this would improve the storage capability of quantum memory devices, such as atomic ensembles that store a state of light that can later be read out optically.

A macroscopic spin state—composed of many individual spins—can be squeezed provided that entanglement can be created within the system. Writing in Physical Review Letters, researchers at the Niels Bohr Institute in Copenhagen report the creation of a spin squeezed state in an ensemble of spin-polarized cesium atoms. They take advantage of entanglement between the nuclear and electronic spin states of the individual ground state atoms, rather than between the electronic spin states of different atoms in the ensemble.

At room temperature, about 1012 cesium atoms, each with a total spin of 4, are confined to a glass cell placed in a magnetic field. An applied laser pulse puts about 98% of the atoms into a state maximally polarized along one axis, creating a coherent spin state (a minimum uncertainty state) with macroscopic spin. Another light pulse creates the entanglement necessary to put the ensemble in a squeezed state. A tomographic reconstruction of the final quantum state verified that a collective spin squeezed state was produced. – Sonja Grondalski


Announcements

More Announcements »

Subject Areas

Quantum InformationOptics

Previous Synopsis

Next Synopsis

Related Articles

Synopsis: Position Detector Approaches the Heisenberg Limit
Quantum Physics

Synopsis: Position Detector Approaches the Heisenberg Limit

The light field from a microcavity can be used to measure the displacement of a thin bar with an uncertainty that is close to the Heisenberg limit. Read More »

Viewpoint: Next Generation Clock Networks
Atomic and Molecular Physics

Viewpoint: Next Generation Clock Networks

Free-space laser links have been used to synchronize optical clocks with an unprecedented uncertainty of femtoseconds. Read More »

Focus: How to Make an Intense Gamma-Ray Beam
Optics

Focus: How to Make an Intense Gamma-Ray Beam

Computer simulations show that blasting plastic with strong laser pulses could produce gamma rays with unprecedented intensity, good for fundamental physics experiments and possibly cancer treatments. Read More »

More Articles