A quantum wedding for two crystals - 21 - ethz.ch
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Press embargo lifts on 04 March at 1800 London time / 1300 US Eastern time A quantum wedding of two crystals A team of researchers lead by Nicolas Gisin and Mikael Afzelius at the University of Geneva are developing a new approach to bring quantum networks to reality, and their latest finding has just been published in Nature Photonics. “What we have demonstrated is that two solid macroscopic objects, namely two 1cm long crystals, can be entangled together. This means that both crystals essentially form a single quantum entity, and that one cannot fully describe the state of each crystal alone,” says Mikael Afzelius. The result is reminiscent of the famous cat of Erwin Schrödinger, except that here, we have two cats such that if one is alive, then the other one is dead, or viceversa. Entanglement means that the two possibilities coexist simultaneously, until someone tries to “look”, which forces one possibility to emerge over the other. In the laboratory, the cats are embodied as rareearthions doped crystals, the same type of crystals that are nowadays widely used in solidstate lasers, and notably in the green laser pointers that everyone can buy. Entanglement in itself is not new; it is routinely produced with photons in many laboratories around the world. However, to go from entanglement between two elementary particles of light, to entanglement between to macroscopic objects, is a challenging task. “Each crystal contains about ten billion rareearth ions that can collectively absorb a single photon. If this single photon is first sent onto a halfsilvered mirror, it emerges as an entangled state of light that can be absorbed by the crystals, thereby transferring the entanglement from light to two solid objects,” explains co author Félix Bussières. The main difficulty is in fact to prove that the crystals have indeed been entangled, which the team achieved by transferring back the entanglement into light and then performing sophisticated measurements on the light particles. But entanglement is not just a striking feature of quantum mechanics: it is a much needed resource for quantum communication. What is envisioned by the researchers is a “quantum internet” where nodes can exchange and processing quantum bits of information. Quantum physics then allows nodes to be entangled, and thus gain the ability to perform important tasks, such as provably secure encryption of messages over distances of a thousand kilometres or more, which is not known to be feasible otherwise. The achievement of the research team is a crucial step towards the realization of practical quantum networks.
Transcript of A quantum wedding for two crystals - 21 - ethz.ch
Press embargo lifts on 04 March at 1800 London time / 1300 US Eastern time A quantum wedding of two crystals
A team of researchers lead by Nicolas Gisin and Mikael Afzelius at the University of Geneva are developing a new approach to bring quantum networks to reality, and their latest finding has just been published in Nature Photonics.
“What we have demonstrated is that two solid macroscopic objects, namely two 1cm-‐long crystals, can be entangled together. This means that both crystals essentially form a single quantum entity, and that one cannot fully describe the state of each crystal alone,” says Mikael Afzelius.
The result is reminiscent of the famous cat of Erwin Schrödinger, except that here, we have two cats such that if one is alive, then the other one is dead, or vice-‐versa. Entanglement means that the two possibilities coexist simultaneously, until someone tries to “look”, which forces one possibility to emerge over the other. In the laboratory, the cats are embodied as rare-‐earth-‐ions doped crystals, the same type of crystals that are nowadays widely used in solid-‐state lasers, and notably in the green laser pointers that everyone can buy.
Entanglement in itself is not new; it is routinely produced with photons in many laboratories around the world. However, to go from entanglement between two elementary particles of light, to entanglement between to macroscopic objects, is a challenging task. “Each crystal contains about ten billion rare-‐earth ions that can collectively absorb a single photon. If this single photon is first sent onto a half-‐silvered mirror, it emerges as an entangled state of light that can be absorbed by the crystals, thereby transferring the entanglement from light to two solid objects,” explains co-‐author Félix Bussières. The main difficulty is in fact to prove that the crystals have indeed been entangled, which the team achieved by transferring back the entanglement into light and then performing sophisticated measurements on the light particles.
But entanglement is not just a striking feature of quantum mechanics: it is a much needed resource for quantum communication. What is envisioned by the researchers is a “quantum internet” where nodes can exchange and processing quantum bits of information. Quantum physics then allows nodes to be entangled, and thus gain the ability to perform important tasks, such as provably secure encryption of messages over distances of a thousand kilometres or more, which is not known to be feasible otherwise. The achievement of the research team is a crucial step towards the realization of practical quantum networks.
Press embargo lifts on 04 March at 1800 London time / 1300 US Eastern time
Source: “Heralded quantum entangled between two crystals” Imam Usmani, Christoph Clausen, Félix Bussières, Nicolas Sangouard, Mikael Afzelius & Nicolas Gisin Nature Photonics (advanced online publication) DOI: 10.1038/NPHOTON.2012.34 (2012) (Journalists should seek to credit the relevant Nature publication as the source of stories covered)
For further information, please contact: Mikael Afzelius Group of Applied Physics University of Geneva Chemin de Pinchat 22 1211 Genève 4 +41 22 379 0507 [email protected]
or
Nicolas Gisin Group of Applied Physics University of Geneva Chemin de Pinchat 22 1211 Genève 4 +41 22 379 0502 [email protected]
For information about the press embargo, please contact:
From North America Neda Afsarmanesh, Nature New York Tel: +1 212 726 9231; Fax: +1 646 563 7117 E-mail: [email protected] From Japan, Korea, China, Singapore and Taiwan Mika Nakano, Nature Tokyo Tel: +81 3 3267 8751; E-mail: [email protected] From the UK/Europe/other countries not listed above Rachel Twinn, Nature London Tel: +44 20 7843 4658; E-mail: [email protected]
