Researchers at the University of Illinois at Urbana-Champaign have constructed a quantum-mechanical state in which the colors of three photons are intertwined with each other. The state is a special combination called the W state, which retains some entanglement, even if one of the three photons is lost, making it useful for quantum communication. Such entangled states also allow new quantum applications and tests of fundamental physics.
The uniqueness of this work is that researchers have used the color or energy of photons as a tangling degree of freedom, whereas previous work has used polarization. The energy of a photon cannot be easily changed, which reduces the possibility of errors when the energy entangled W state propagates over a long distance. The condition is checked for the first time by measuring information about the two photon subsystems. Their findings were published in Physical Review Letters .
"People have created W states that have been intertwined with polarization," notes Bin Fang, a graduate student in the project. "However, this is the first discrete W-state entangled with energy and the first three-photon entangled state created in optical fiber."
To create the state, researchers shine a laser in a glass fiber. Through a process called spontaneous four-wave mixing, four laser photons interact with the fiber and are destroyed to create two pairs of photons of different colors (for example, two red and green photons). These four photons are used to construct the 3-photon W state. One of them is detected as green, leaving the other three entangled as W states, consisting of all possible iterations of two red photons and a green photon at one time.
Comparison of twisted photons by radial position and moment
B. Fang et al, A three-photon discrete energy entangled W state in optical fiber, Physical Review Letters (2019). Doi: 10.1103 / PhysRevLett.123.070508
The University of Illinois at Urbana-Champagne
Researchers create the first W-state with three photons intertwined with color (2019, September 23)
Downloaded September 23, 2019
This document is copyright. Apart from any fair dealing for private or research purposes, no
part may be reproduced without written permission. Content is provided for information only.