- Category: Science & Technology
by Colin Barras - NewScientist.com Photo: Photons emitted in a coherent beam from a laser. Physicists have created a "fat" particle made of a record-breaking five entangled photons in a quantum state with echoes of Schrödinger's cat. Such photons could be put to use in high-resolution imaging. The physical properties of entangled particles are intimately linked, even across vast distances. Physicists want to entangle ever-larger numbers of particles to understand why the phenomenon isn't seen at the macroscopic scale.
It's already possible to entangle six photons in a so-called graph state – ideal for quantum computing because each particle occupies a unique mode, or route, through a quantum circuit.
Photo Image: The wavefronts resulting from the interference of two coherent point-sources 40 wavelengths apart.
But another form of entanglement that is employed in high-resolution imaging has been stalled at three or four photons – until now.
In a "NOON" state, if the entangled photons are given a choice of two paths through an optical medium, all will opt to follow the same one. As such, a NOON state is comparable to Erwin Schrödinger's famous thought experiment, in which a cat can occupy only one of two states – alive or dead – when it is hidden in a box and exposed to a potentially lethal source.
Now Itai Afek, Oron Ambar and Yaron Silberberg at the Weizmann Institute of Science in Rehovot, Israel, have pushed the number of photons entangled in the NOON state up to a record-breaking five.
Split pulses
They used a laser to generate short pulses of infrared light and split each pulse in two. They then converted one half into a quantum pulse, using a transparent crystal of beta barium borate to cleave some of the photons into entangled pairs that behave in a correlated way. Finally, they combined this quantum pulse with the other half of the pulse, theoretically generating a NOON state containing up to five entangled photons...MORE...
