Quantum entanglement: Going large

Particles small enough for their behaviour to be governed by the laws of quantum mechanics can exhibit a remarkable property known as entanglement. A pair of quantum particles can exist in entangled 'superposition', a mixture of states that resolves only when some physical property such as spin or polarization is measured. Quantum entanglement is a fundamental requirement for quantum computing, but until now it has been possible only to generate entanglement between microscopic particles. Using a new method of generating entanglement, an entangled state involving two macroscopic objects, each consisting of a caesium gas sample containing about 10¹² atoms, has now been created. The entangled spin state can survive for 0.5 milliseconds, a long time in this context, bringing practical applications of quantum memory and quantum teleportation a little closer.

Experimental long-lived entanglement of two macroscopic objects
BRIAN JULSGAARD, ALEXANDER KOZHEKIN & EUGENE S. POLZIK
Nature 413, 400-403 (27 September 2001)
| First Paragraph | Full Text | PDF (175 K) |

Quantum physics: Entangled atomic samples
J. IGNACIO CIRAC
Quantum mechanics has potential applications in communication and computation. But first a quantum connection — known as entanglement — has to be created between bigger and bigger objects.
Nature 413, 375-377 (27 September 2001)
| Full Text | PDF (106 K) |

Trillion-atom triumph

27 September 2001 table of contents